Set Theory Talks

Global set theory seminar and conference announcements

Logic Seminar 20 March 2024 17:00 hrs by Sun Mengzhou

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 20 March 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Speaker: Sun Mengzhou Title: The Kaufmann-Clote question on end extensions of models of arithmetic URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html A general question in the model theory of arithmetic is: For each theories S, T and natural number n, is it true that every countable sufficiently saturated model of S has a proper n-elementary end extension to a model of a T? Efforts over the past four decades have revealed answers to this question for S and T in the induction-collection hierarchy IΣ_n, BΣ_n, except the following instance by Clote and Kaufmann: Is it true that, given any integer n, every countable model of BΣ_n+2 has a proper n-elementary end extension to a model of BΣ_n+1? We present a positive answer to the Kaufmann-Clote question. The proof consists of a second-order ultrapower construction based on a low basis theorem. We also include a survey on the results related to the general question above. This is a joint work with Tin Lok Wong and Yue Yang.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 18, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 18, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Michał Godziszewski (Warsaw).
Title: Modal quantifiers, potential infinity, and Yablo sequences

Abstract: When properly arithmetized, Yablo’s paradox results in a set of formulas which (with local disquotation in the background) turns out to be consistent, but omega-inconsistent. Adding either uniform disquotation or the omega-rule results in  inconsistency. Since the paradox involves an infinite sequence of sentences, one might think that it doesn’t arise in finitary contexts. We study whether it does. It turns out that the issue depends on how the finitistic approach is formalized. On one of them, proposed by Marcin Mostowski, all the paradoxical sentences simply fail to hold. This happens at a price: the underlying finitistic arithmetic itself is omega-inconsistent. Finally, when studied in the context of a finitistic approach which preserves the truth of standard arithmetic, the paradox strikes back — it does so with double force, for now the inconsistency can be obtained without the use of uniform disquotation or the omega-rule.

Note: This is joint work with Rafał Urbaniak (Gdańsk).




- - - - Tuesday, Mar 19, 2024 - - - -

MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Virtual (email Victoria Gitman for meeting id)
Tuesday, March 19, 1pm

Roman Kossak, CUNY
The lattice problem for models of PA

The lattice problem for models of PA is to determine which lattices can be represented either as lattices of elementary substructures of a model of PA or, more generally, which can be represented as lattices of elementary substructures of a model N that contain a given elementary substructure M of N. I will talk about the history of the problem, from the seminal paper of Haim Gaifman from 1976 and other early results to some recent work of Jim Schmerl. There is much to talk about.



Computational Logic Seminar  
Spring 2024 
(online)
Tuesday, March 19, Time 2:00 - 4:00 PM 
zoom link: contact Sergei Artremov sartemov@gmail.com
SpeakerTudor ProtopopescuCUNY
Title: Logics of Intuitionistic Knowledge and Verification

Abstract: We present intuitionistic epistemic systems IEL-, IEL and IEL+, systems of verification based belief, knowledge and strict knowledge. The intuitionistic epistemic language captures basic reasoning about intuitionistic knowledge and belief, but its language has expressive limitations. Following Gödel's explication of IPC as a fragment of the more expressive system of classical modal logic S4, we present a faithful embedding of the intuitionistic systems into S4 extended with a verification modality. These systems in turn have explicit counterparts in the Logic of Proofs extended with a verification modality.



- - - - Wednesday, Mar 20, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Sina Hazratpour, Johns Hopkins University.

Date and Time:     Wednesday March 20, 2024, 7:00 - 8:30 PM.

Title:     Fibred Categories in Lean.


Abstract: Fibred categories are one of the most important and useful concepts in category theory and its application in categorical logic. In this talk I present my recent formalization of fibred categories in the interactive theorem prover Lean 4. I begin by highlighting certain technical challenges associated with handling the equality of objects and functors within the extensional dependent type system of Lean, and how they can be overcome. In this direction, I will demonstrate how we can take advantage of dependent coercion, instance synthesis, and automation tactics from the Lean toolbox. Finally I will discuss a formalization of Homotopy Type Theory in Lean 4 using a fired categorical framework.




- - - - Thursday, Mar 21, 2024 - - - -



- - - - Friday, Mar 22, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 22, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.

Arthur Apter, CUNY
A choiceless answer to a question of Woodin

In a lecture presented in July 2023, Moti Gitik discussed the following question from the 1980s due to Woodin, as well as approaches to its solution and why it is so difficult to solve:

Question: Assuming there is no inner model of ZFC with a strong cardinal, is it possible to have a model  of ZFC such that ' and  for every ', together with the existence of an inner model  of ZFC such that for the  so that  and  ' is measurable and '?

I will discuss how to find answers to this question, if we drop the requirement that  satisfies the Axiom of Choice. I will also briefly discuss the phenomenon that on occasion, when the Axiom of Choice is removed from consideration, a technically challenging question or problem becomes more tractable. One may, however, end up with models satisfying conclusions that are impossible in ZFC.

Reference: A. Apter, 'A Note on a Question of Woodin', Bulletin of the Polish Academy of Sciences (Mathematics), volume 71(2), 2023, 115--121.



Logic Workshop
CUNY Graduate Center
Friday Mar 22, 2:00pm-3:30pm, Room 5417
Kameryn Williams, Bard College at Simon's Rock

Mediate cardinals

In the late 1910s Bertrand Russell was occupied with two things: getting into political trouble for his pacifism and trying to understand the foundations of mathematics. His students were hard at work with him on this second occupation. One of those students was Dorothy Wrinch. In 1923 she gave a characterization of the axiom of choice in terms of a generalization of the notion of a Dedekind-finite infinite set. Unfortunately, her career turned toward mathematical biology and her logical work was forgotten by history.

This talk is part of a project of revisiting Wrinch's work from a modern perspective. I will present the main result of her 1923 paper, that AC is equivalent to the non-existence of what she termed mediate cardinals. I will also talk about some new independence results. The two main results are: (1) the smallest  for which a -mediate cardinal exists can consistently be any regular  and (2) the collection of regular  for which exact -mediate cardinals exist can consistently be any class.



Next Week in Logic at CUNY:

- - - - Monday, Mar 25, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 25, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Dan Marshall (Lingnan)
Title: A moderate theory of overall resemblance

Abstract: This paper defends the moderate theory of overall resemblance stated by: A) y is at least as similar to x as z is iff: i) every resemblance property shared by x and z is also shared by x and y, and ii) for any resemblance family of properties F, y is at least as similar to x as z is with respect to F. In this account, a resemblance property is a property that corresponds to a genuine respect in which two things can resemble each other, whereas a resemblance family is a set of properties with respect to which things can be more or less similar to each other. An example of a resemblance property is being cubical, an example of a non-resemblance property is being either a gold cube or a silver sphere, and an example of a resemblance family is the set of specific mass properties.



- - - - Tuesday, Mar 26, 2024 - - - -



- - - - Wednesday, Mar 27, 2024 - - - -



- - - - Thursday, Mar 28, 2024 - - - -



- - - - Friday, Mar 29, 2024 - - - -

** NO CLASSES AT CUNY GRADUATE CENTER **


- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
Groups, Logic, and Dynamics
This is the second installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

KGRC Talk - March 21

Kurt Godel Research Center
KGRC/Institute of Mathematics invites you to the following Set Theory Seminar talk: ”(Piecewise) convexembeddability on linear orders” M. Iannella (TU Wien) Kolingasse 14–16, 1090, 1st floor, SR 10, Thursday, March 21, 11:30am–1:00pm, hybride mode Given a nonempty set $\mathcal{L}$ of linear orders, we say that the linear order $L$ is $\mathcal{L}$-convex embeddable into the linear order $L'$ if it is possible to partition $L$ into convex sets, indexed by some element of $\mathcal{L}$, which are isomorphic to convex subsets of $L'$ ordered in the same way. This notion generalizes convex embeddability and (finite) piecewise convex embeddability, which arise from the special cases $\mathcal{L}=\{\mathbf{1}\}$ and $\mathcal{L}=\mathsf{Fin}$. In this talk we focus on the behaviour of these relations on the set of countable linear orders, first characterising when they are transitive, and hence a quasi-order. We then look at some combinatorial properties and complexity (with respect to Borel reducibility) of these quasi-orders. Finally, we analyse their extension to uncountable linear orders. The presented results stem from joint work with Alberto Marcone, Luca Motto Ros, and Vadim Weinstein. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. ******* Video recordings available so far of the Set Theory Seminar: March, 7: S. Hovath (ETH Zurich, CH, "Magic Sets" https://ucloud.univie.ac.at/index.php/s/LeTqoZN7aHCqDd5 March, 7: F. Uribe Zapata (TU Wien), "A general theory of iterated forcing using finitely additive measures" https://ucloud.univie.ac.at/index.php/s/kEwfXg8PNFp44MC ******* Updates at https://kgrc.univie.ac.at/eventsnews/ -- Mag. Petra Czarnecki de Czarnce-Chalupa Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16, #7.48 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

Set theory and topology seminar 19.03.2024 Piotr Szewczak

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in set theory and topology (on Tuesday 19.03.2024 at 17:15 in room A.4.1 C-19  (Wrocław University of Science and Technology) the lecture:
"Perfectly meager sets in the transitive sense and the Hurewicz property"
will be presented by

Piotr Szewczak (UKSW)


Abstract: 
We work in the Cantor space with the usual group operation +. A set X  is perfectly meager in the transitive sense if for any perfect set P there is an F-sigma set F containing X such that for every point t the intersection of t+F and P is meager in the relative topology of P. A set X is Hurewicz if for any sequence of increasing open covers of X one can select one set from each cover such that the chosen sets formulate a gamma-cover of X, i.e., an infinite cover such that each point from X belongs to all but finitely many sets from the cover. Nowik proved that each Hurewicz set which cannot be mapped continuously onto the Cantor set is perfectly meager in the transitive sense. We answer a question of Nowik and Tsaban, whether of the same assertion holds for each Hurewicz set with no copy of the Cantor set inside. We solve this problem, under CH, in the negative. 
This is a joint work with Tomasz Weiss and Lyubomyr Zdomskyy. 
The research was funded by the National Science Centre, Poland  and the Austrian Science Found under the Weave-UNISONO call in the Weave programme, project: Set-theoretic aspects of topological selections 2021/03/Y/ST1/00122

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)


About 15 minutes before the seminar we invite you for coffee and a chat to social room A.4.1.A in C-19. 


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 20th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Allen Gehret -- Asymptotic couples and set theory The subject ``asymptotic differential algebra'' has recently gained attention with the tremendous landmark results of Aschenbrenner, van den Dries, and van der Hoeven in the volume ``Asymptotic differential algebra and model theory of transseries''. In this talk I will describe a small piece of this world which I have been investigating, and its connection to set theory. The outline of the talk is as follows: I. 1-variable calculus, a "review" II. Asymptotic couples III. Dividing lines and set-theoretic independence results IV. Current/future work? (joint with Elliot Kaplan, Nigel Pynn-Coates,...) Best, David

47th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the morning.


Our speaker this week will be Sumun Iyer from Cornell University. This talk is going to take place this Friday,  Mar 15,  from 9am to 10am(UTC+8, Beijing time). 


Title: Extremely amenable groups of homeomorphisms

Abstract: A topological group is extremely amenable if every continuous action of it on a compact Hausdorff space has a fixed point. We will first survey some known results/ general tools about extreme amenability for homeomorphism groups of connected compact spaces. We discuss a construction due to Uspenskij which gives a condition equivalent to extreme amenability for this setting. We then show a Ramsey-type statement for subsets of simplices that, together with Uspenskij's construction, gives a new proof of a theorem due to Pestov: that the group of orientation-preserving homeomorphisms of the closed unit interval is extremely amenable. This is a joint work with Lukas Michel and Alex Scott.
___________________________________________________________________________________________________________________________________________________


This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title :The 47th Nankai Logic Colloquium -- Sumun Iyer 

Time :9:00am, Mar. 15, 2024(Beijing Time)

Zoom Number : 734 242 5443

Passcode :477893

Link :https://zoom.us/j/7342425443?pwd=EG6I3uatr8anqkk6HM5wZ9FKjhkjbC.1&omn=87197636384

_____________________________________________________________________


Best wishes,

Ming Xiao




This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 11, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 11, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Otávio Bueno (Miami)
Title: Dispensing with the grounds of logical necessity

Abstract: Logical laws are typically conceived as being necessary. But in virtue of what is this the case? That is, what are the grounds of logical necessity? In this paper, I examine four different answers to this question in terms of: truth-conditions, invariance of truth-values under different interpretations, possible worlds, and brute facts. I ultimately find all of them wanting. I conclude that an alternative conception of logic that dispenses altogether with grounds of logical necessity provides a less troublesome alternative. I then indicate some of the central features of this conception.




- - - - Tuesday, Mar 12, 2024 - - - -

MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Tuesday, March 12, 1pm

Albert Visser, Utrecht University
Restricted completions

This talk reports on research in collaboration with Ali Enayat and Mateusz Łełyk.

Steffen Lempp and Dino Rossegger asked: is there a consistent completion of  that is axiomatised by sentences of bounded quantifier-alternation complexity? We show that there is no such restricted completion. We also show that, if one changes the measure of complexity to being , there is a restricted completion. Specifically, we show that the true theory of the non-negative part of  can be axiomatised by a single sentence plus a set of -sentences.

In our talk we will sketch these two answers. One of our aims is to make clear is that the negative answer for the case of quantifier-alternation complexity simply follows from Rosser's Theorem viewed from a sufficiently abstract standpoint.




- - - - Wednesday, Mar 13, 2024 - - - -



- - - - Thursday, Mar 14, 2024 - - - -



- - - - Friday, Mar 15, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 15, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Chris Lambie-Hanson, Czech Academy of Sciences

Squares, ultrafilters and forcing axioms

A uniform ultrafilter  over a cardinal  is called indecomposable if, whenever  and , there is a set  such that  is countable. Indecomposability is a natural weakening of -completeness and has a number of implications for, e.g., the structure of ultraproducts. In the 1980s, Sheard answered a question of Silver by proving the consistency of the existence of an inaccessible but not weakly compact cardinal carrying an indecomposable ultrafilter. Recently, however, Goldberg proved that this situation cannot hold above a strongly compact cardinal: If  is strongly compact and  carries an indecomposable ultrafilter, then  is either measurable or a singular limit of countably many measurable cardinals. We prove that the same conclusion follows from the Proper Forcing Axiom, thus adding to the long list of statements first shown to hold above a strongly compact or supercompact cardinal and later shown also to follow from PFA. Time permitting, we will employ certain indexed square principles to prove that our results are sharp. This is joint work with Assaf Rinot and Jing Zhang.



Logic Workshop
CUNY Graduate Center
Friday Mar 15, 2:00pm-3:30pm, Room 5417
Michał Godziszewski, University of Warsaw

Tennebaum's Theorem for quotient presentations and model-theoretic skepticism

A computable quotient presentation of a mathematical structure  consists of a computable structure on the natural numbers , meaning that the operations and relations of the structure are computable, and an equivalence relation  on , not necessarily computable but which is a congruence with respect to this structure, such that the quotient  is isomorphic to the given structure . Thus, one may consider computable quotient presentations of graphs, groups, orders, rings and so on.
A natural question asked by B. Khoussainov in 2016, is if the Tennenbaum Thoerem extends to the context of computable presentations of nonstandard models of arithmetic. In a joint work with J.D. Hamkins we have proved that no nonstandard model of arithmetic admits a computable quotient presentation by a computably enumerable equivalence relation on the natural numbers.
However, as it happens, there exists a nonstandard model of arithmetic admitting a computable quotient presentation by a co-c.e. equivalence relation. Actually, there are infinitely many of those. The idea of the proof consists is simulating the Henkin construction via finite injury priority argument. What is quite surprising, the construction works (i.e. injury lemma holds) by Hilbert's Basis Theorem. The latter argument is joint work with T. Slaman and L. Harrington.




Next Week in Logic at CUNY:

- - - - Monday, Mar 18, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 18, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Michał Godziszewski (Warsaw).
Title: Modal quantifiers, potential infinity, and Yablo sequences

Abstract: When properly arithmetized, Yablo’s paradox results in a set of formulas which (with local disquotation in the background) turns out to be consistent, but omega-inconsistent. Adding either uniform disquotation or the omega-rule results in  inconsistency. Since the paradox involves an infinite sequence of sentences, one might think that it doesn’t arise in finitary contexts. We study whether it does. It turns out that the issue depends on how the finitistic approach is formalized. On one of them, proposed by Marcin Mostowski, all the paradoxical sentences simply fail to hold. This happens at a price: the underlying finitistic arithmetic itself is omega-inconsistent. Finally, when studied in the context of a finitistic approach which preserves the truth of standard arithmetic, the paradox strikes back — it does so with double force, for now the inconsistency can be obtained without the use of uniform disquotation or the omega-rule.

Note: This is joint work with Rafał Urbaniak (Gdańsk).




- - - - Tuesday, Mar 19, 2024 - - - -



- - - - Wednesday, Mar 20, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Sina Hazratpour, Johns Hopkins University.

Date and Time:     Wednesday March 20, 2024, 7:00 - 8:30 PM.

Title:     Fibred Categories in Lean.


Abstract: Fibred categories are one of the most important and useful concepts in category theory and its application in categorical logic. In this talk I present my recent formalization of fibred categories in the interactive theorem prover Lean 4. I begin by highlighting certain technical challenges associated with handling the equality of objects and functors within the extensional dependent type system of Lean, and how they can be overcome. In this direction, I will demonstrate how we can take advantage of dependent coercion, instance synthesis, and automation tactics from the Lean toolbox. Finally I will discuss a formalization of Homotopy Type Theory in Lean 4 using a fired categorical framework.




- - - - Thursday, Mar 21, 2024 - - - -



- - - - Friday, Mar 22, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 22, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.

Arthur Apter, CUNY
A choiceless answer to a question of Woodin

In a lecture presented in July 2023, Moti Gitik discussed the following question from the 1980s due to Woodin, as well as approaches to its solution and why it is so difficult to solve:

Question: Assuming there is no inner model of ZFC with a strong cardinal, is it possible to have a model  of ZFC such that ' and  for every ', together with the existence of an inner model  of ZFC such that for the  so that  and  ' is measurable and '?

I will discuss how to find answers to this question, if we drop the requirement that  satisfies the Axiom of Choice. I will also briefly discuss the phenomenon that on occasion, when the Axiom of Choice is removed from consideration, a technically challenging question or problem becomes more tractable. One may, however, end up with models satisfying conclusions that are impossible in ZFC.

Reference: A. Apter, 'A Note on a Question of Woodin', Bulletin of the Polish Academy of Sciences (Mathematics), volume 71(2), 2023, 115--121.



Logic Workshop
CUNY Graduate Center
Friday Mar 22, 2:00pm-3:30pm, Room 5417
Kameryn Williams Bard College at Simon's Rock



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
Groups, Logic, and Dynamics
This is the second installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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KGRC Talks - March 11-15

Kurt Godel Research Center
KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14–16, 1090, 1st floor, SR 10, Thursday, March 14, 11:30am–1:00pm. ”How economists forgot about multi-player utility and how we remembered” D. Schrittesser (Harbin Institute of Technology, Harbin, CN) This is all joint work with Ali M. Khan (Johns Hopkins) and Paul Arthur Pedersen (CUNY). Game theory as practiced by economists is often couched in a setting where players pick strategies, and then a utility function tells them who has which pay off (the so-called ”normal form” of a game). For two person games, an important special case is the zero sum game: the case where pay offs always sum to zero. Aumann, the sixties, defined ”strictly competitive games”, two player games in which what is good for one player is bad for the other. Aumann frequently stated that this is the same class as the zero sum games—for an appropriate choice of utility function (and provided the players strategy spaces are closed under mixing). We claim that Aumann must have known this because he knew the multidimensional theory of utility. But then in 2009, Adler, Daskalakis and Papadimitriou gave a non-trivial proof of the fact claimed by Aumann, for finite games, claiming that no such proof exists in the literature. This was generalized in 2023 by Rai- mondo to games where the set of strategies available to each player is an appropriate set of probability measures on [0,1] (or if you’re feeling fancy, on a standard Borel space). In this talk, I shall show what Aumann and others must already have been aware of, but what has apparently been forgotten in the meantime: That these results, and more general ones, follow easily from the theory of mutlidimensional utility developed in the 60ies and early 70ies by Fishburn, Roberts, and others. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, March 14, 3:00pm–3:50pm, hybrid mode ”Projective Fraisse limits of trees” Aleksandra Kwiatkowska (University of Münster, DE*)* We continue the study of projective Fraisse limits developed by Irwin-Solecki and Panagiotopoulos-Solecki by investigating families of epimorphisms between finite trees and finite rooted trees. We focus on particular classes of epimorphisms such as monotone, confluent or simple confluent, which are adaptations to graphs of monotone or confluent maps from continuum theory. As the topological realizations of the projective Fraisse limits we obtain the dendrite D_3 the Mohler-Nikiel universal dendroid, as well as new, interesting compact connected spaces (continua) for which we do not yet have topological characterizations. The talk is based on joint work with Charatonik, Roe, Yang. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to aristotelis.panagiotopoulos@univie.ac.at.

Set theory and topology seminar 12.03.2024 Grigor Sargsyan

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in set theory and topology (on Tuesday 12.03.2024 at 17:15 in room A.4.1 C-19  (Wrocław University of Science and Technology) the lecture:
"Forcing extensions of models of determinacy"
will be presented by

Grigor Sargsyan (IMPAN)


Abstract: 
We will give an overview of what has been recently forced over models of determinacy. In particular,  we will
explain how to obtain combinatorially rich ZFC extensions by forcing over a model of determinacy axioms. Part of this work\
are joint with Paul Larson and Douglas Blue.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)


About 15 minutes before the seminar we invite you for coffee and a chat to social room A.4.1.A in C-19. 


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 13th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Stefan Geschke -- Separating Borel chromatic numbers We discuss various graphs on the Cantor space and discuss the question whether their Borel chromatic numbers can consistently be different. Moreover, there will be an extra seminar this week, Friday March 8th, 14:00--15:30, Institute of Mathematics CAS, seminar room Konirna, organized by Wieslaw Kubis. Program: Lionel Nguyen Van The -- Revisiting the Erdös-Rado canonical partition theorem One of the numerous strengthenings of Ramsey's theorem is due to Erdös and Rado, who analyzed what partition properties can be obtained on m-subsets of the naturals when colorings are not necessarily finite. Large monochromatic sets may not appear in that case, but there is a finite list of behaviors, called "canonical", to which every coloring reduces. The purpose of this talk will be to remind certain not so well known analogous theorems of the same flavor that were obtained by Prömel in the eighties for various classes of structures (like graphs or hypergraphs), and to show how such theorems can in fact be deduced in the more general setting of Fraïssé classes. Best, David

KGRC Set Theory Talks - March 4-8

Kurt Godel Research Center
The KGRC welcomes as guests:

Alexi Block Gorman, Ohio State University, Columbus, US (host: Matthias Aschenbrenner) visits March 3–9

Elliot Kaplan, McMaster University, Hamilton, CA, Columbus, US (host: Nigel Pynn-Coates) visits March 3–9

Silvan Horvath, ETH Zurich, CH (host: Vera Fischer) visits March 4–July 31

* * * * * * * * *

KGRC/Institute of Mathematics invites you to the following talks:
(updates at https://kgrc.univie.ac.at/) )


SET THEORY SEMINAR
Kolingasse 14–16, 1090, 1st floor, SR 10,
Thursday, March 7, 11:30am – 12:00pm, hybrid mode

”Magic Sets”
S. Horvath (ETH Zurich, CH)


A Magic Set is a set M of reals with the property that for all nowhere constant, continuous functions f and
g on the reals it holds that f [M ] ⊆ g[M ] implies f = g.
I will cover some of the basic results on magic sets and introduce magic forcing - a forcing notion that adds
a new magic set to the ground model.

Zoom: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at.
Meeting ID: 671 1734 6051
Passcode: kgrc
Please direct any questions about this talk to vera.fischer@univie.ac.at.

* * * * * * * * *

SET THEORY SEMINAR
Kolingasse 14–16, 1090, 1st floor, SR 10,
Thursday, March 7, 12:00pm – 13:00pm, hybrid mode

”A general theory of iterated forcing using finitely additive measures”
A. F. Uribe Zapata (TU Wien)


Saharon Shelah in 2000 introduced a finite-support iteration using finitely additive measures to prove that,
consistently, the covering of the null ideal may have countable cofinality. In 2019, Jakob Kellner, Saharon
Shelah, and Anda R. T ̆anasie achieved some new results and applications using such iterations.

In this talk, based on the works mentioned above, we present a general theory of iterated forcing using
finitely additive measures, which was developed in the speaker’s master’s thesis. For this purpose, we intro-
duce two new notions: on the one hand, we define a new linkedness property, which we call ”FAM-linked”
and, on the other hand, we generalize the idea of intersection number to forcing notions, which justifies the
limit steps of our iteration theory. Finally, we show a new separation of the left-side of Cicho ́n’s diagram
allowing a singular value.

Zoom info
Zoom: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at.
Passcode: kgrc
Please direct any questions about this talk to vera.fischer@univie.ac.at.


* * * * * * * * *

VIDEO recordings available so far of the LOGIC COLLOQUIUM:
January 25: Y. Khomskii (Amsterdam U College, NL and U Hamburg, DE) "Trees, Transcendence and Quasi-generic reals"https://ucloud.univie.ac.at/index.php/s/Wd9DPzXqQsnBPzC
November 16: D. A. Mejía (Shizuoka U, JP) ”Iterations with ultrafilter-limits and fam-limits” https://ucloud.univie.ac.at/index.php/s/T6pD2XgwTfNPYtn

—–

The LECTURE NOTE for Diego Mejía’s mini-course available so far of the Set Theory Seminar:
January 25: D. A. Mejıa (Shizuoka U, JP) ”Forcing techniques for Cicho ́n’s Maximum” https://mathematik.univie.ac.at/fileadmin/user_upload/f_mathematik/Events_News/Vortraege_Events/2023-24/20240122_Mejia_minicourse-1.pdf.

VIDEO recordings available so far of the SET THEORY SEMINAR:
January 25: D. A. Mejía (Shizuoka U, JP), ”Forcing techniques for Cicho ́n’s Maximum VI” video: https://ucloud.univie.ac.at/index.php/s/8EyKfLZW3NBH4f2
January 18: D. A. Mejía (Shizuoka U, JP), ”Forcing techniques for Cicho ́n’s Maximum V” video:https://ucloud.univie.ac.at/index.php/s/QrKjY6CYtJMx7WT
January 11: D. A. Mejía (Shizuoka U, JP), ”Forcing techniques for Cicho ́n’s Maximum IV” https://ucloud.univie.ac.at/index.php/s/KFpbqsLjQm3tcKn
December 12: "Forcing techniques for Cichoń's Maximum: Preservation theory for cardinal characteristics III" video : https://ucloud.univie.ac.at/index.phps/rddck2AZwnPp39r
December 7: "Forcing techniques for Cichoń's Maximum: FS iterations II" video:https://ucloud.univie.ac.at/index.php/s/iwqKFiYCEpPaPsN
November 30: "Forcing techniques for Cichoń's Maximum I" video: https://ucloud.univie.ac.at/index.php/s/xWjSe9eA92ReRV9
-- 
Mag. Petra Czarnecki de Czarnce-Chalupa
Institute of Mathematics (Kurt Goedel Research Center, Logic)
University of Vienna
Kolingasse 14-16, #7.48
1090 Vienna, Austria
Phone: +43/ (0)1 4277-50501

NUS Logic Seminar Talk by Rupert Hoelzl on 6 March 2024 17:00 hrs

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 6 March 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Speaker: Rupert Hoelzl, Universitaet der Bundeswehr, Munich Title: Benign approximations and non-speedability Abstract: A left-computable number x is called regainingly approximable if there is a computable increasing sequence (x_n)_{n in N} of rational numbers converging to x such that x-x_n < 2^-n. for infinitely many n in N; and it is called nearly computable if there is such an (x_n)_n such that for every computable increasing function s:N -> N the sequence (x_{s(n+1)}-x_{s(n)}){n in N} converges computably to 0. In this talk we study the relationship between both concepts by constructing on the one hand a non-computable number that is both regainingly approximable and nearly computable, and on the other hand a left-computable number that is nearly computable but not regainingly approximable; it then easily follows that the two notions are incomparable with non-trivial intersection. With this relationship clarified, we then hold the keys to answering an open question of Merkle and Titov: they studied speedable numbers, that is, left-computable numbers whose approximations can be sped up in a certain sense, and asked whether, among the left-computable numbers, being Martin-Loef random is equivalent to being non-speedable. As we show that the concepts of speedable and regainingly approximable numbers are equivalent within the nearly computable numbers, our second construction provides a negative answer. This is joint work with Philip Janicki. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Set theory and topology seminar 5.03.2024 Agnieszka Widz

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in set theory and topology (on Tuesday 5.03.2024 at 17:15 in room A.4.1 C-19  (Wrocław University of Science and Technology) the lecture:
"Random Graph"
will be presented by

Agnieszka Widz


Abstract: 
The Random Graph can be generated almost surely by connecting vertices with a fixed probability $p\in(0,1)$, independently of other pairs. In my talk, I will recall the construction and explore interesting properties of the Random Graph, investigating the impact of varying probabilities for each edge. Specifically, I will characterize sequences $(p_n)_{n\in\IN}$ for which there exists a bijection $f$  between pairs of vertices in $\IN$, such that if we connect vertices $v$ and $w$ with probability $p_{f(\{v,w\})}$, the Random Graph emerges almost surely.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)


About 15 minutes before the seminar we invite you for coffee and a chat to social room A.4.1.A in C-19. 


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 4, 2024 - - - -

Rutgers Logic Seminar
Monday, March 4, 3:30pm, Rutgers University, Hill 705
Sean Cox, Virginia Commonwealth
Sparse systems, CH, and Denjoy-Carleman classes

Abstract:  Hardin and Taylor proved that, for any set $S$, a wellordering of ${}^{\mathbb{R}} S$ allows one to build a "predictor" $\mathcal{P}$ for partial functions from $\mathbb{R} \to S$, in the sense that for any total $F \in  {}^{\mathbb{R}} S$, $\mathcal{P}(F \restriction (-\infty,t)) = F(t)$ for almost every $t \in \mathbb{R}$.  They asked:  for which classes $\Gamma \subseteq \text{Homeo}^+(\mathbb{R})$ could one further arrange that $\mathcal{P}$ is invariant with respect to precomposition with members of $\Gamma$?  Subsequent work of Hardin-Taylor,  Bajpai-Velleman, and my joint work with Aldi, Buffkin, Cline, Cody, Elpers, and Lee have made progress on this problem.  This talk will focus on the negative direction:  if $\Gamma$ carries a "sparse system", then there is no $\Gamma$-invariant predictor.  In recent work with Aldi, Buffkin, and Cline, we proved that 1) sparse systems always exist for "non-quasi-analytic" Denjoy-Carleman classes, and 2) CH holds if and only if some--equivalently, every--quasi-analytic Denjoy Carleman class carries a sparse system.  The latter strengthens the previous Cody-Cox-Lee result that CH is equivalent to existence of a sparse analytic system.


Logic and Metaphysics Workshop
Date: Monday, March 4, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Elise Crull (CUNY).
Title: Declaring no dependence

Abstract: Viable fundamental ontologies require at least one suitably stable, generic-yet-toothy metaphysical dependence relation to establish fundamentality. In this talk I argue that recent experiments in quantum physics using Page-Wootters devices to model global vs. local dynamics cast serious doubt on the existence of such metaphysical dependence relations when – and arguably, inevitably within any ontological framework – physical systems serve as the relata.



- - - - Tuesday, Mar 5, 2024 - - - -

MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Tuesday, March 5, 1pm
Virtual: email Victoria Gitman (vgitman@gmail.com) for meeting id
Piotr Gruza University of Warsaw

Tightness and solidity in fragments of Peano Arithmetic

It was shown by Visser that Peano Arithmetic has the property that no two distinct extensions of it (in its language) are bi-interpretable. Enayat proposed to refer to this property of a theory as tightness and to carry out a more systematic study of tightness and its stronger variants, which he called neatness and solidity.

Enayat proved that not only , but also , and  are solid; and on the other hand, that finitely axiomatisable fragments of them are not even tight. Later work by a number of authors showed that many natural proper fragments of these theories are also not tight.

Enayat asked whether there are proper solid subtheories (containing some basic axioms that depend on the theory) of the theories listed above. We answer this question in the case of  by proving that for every  there exists a solid theory strictly between  and . Furthermore, we can require that the theory does not interpret , and that if any true arithmetic sentence is added to it, the theory still does not prove .

Joint work with Leszek Kołodziejczyk and Mateusz Łełyk.



Computational Logic Seminar  
Spring 2024 (online) For a zoom link contact S.Artemov
Tuesday, March 5, Time 2:00 - 4:00 PM
Speaker: Sergei Artemov, Graduate Center
Title: On Tolerance Analysis in Extensive-Form Games.

Abstract: Epistemic assumptions, including rationality of actors, can change during the game, e.g., due to unexpected moves of players. We discuss a body of examples and outline the corresponding logic foundation of belief revision in games.

 

- - - - Wednesday, Mar 6, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Jean-Pierre Marquis, Universite de Montreal.

Date and Time:     Wednesday March 6, 2024, 7:00 - 8:30 PM. IN PERSON TALK!

Title:     Hom sweet Hom: a sketch of the history of duality in category theory.


Abstract: Duality, in its various forms and roles, played a surprisingly important part in the development of category theory. In this talk, I will concentrate on the development of these forms and roles that lead to the categorical formulation of Stone-type dualities in the 1970s. I will emphasize the epistemological gain and loss along the way.




- - - - Thursday, Mar 7, 2024 - - - -



- - - - Friday, Mar 8, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 8, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Jonathan Osinski University of Hamburg

We consider logics in which the collection of sentences over a set-sized vocabulary can form a proper class. The easiest example of such a logic is , which allows for disjunctions and conjunctions over arbitrarily sized sets of formulas and quantification over strings of variables of any infinite length. Model theory of  is very restricted. For instance, it is inconsistent for it to have nice compactness or Löwenheim-Skolem properties. However, Trevor Wilson recently showed that the existence of a Löwenheim-Skolem-Tarski number of a certain class-sized fragment of  is equivalent to the existence of a supercompact cardinal, and various other related results. We continue this work by considering several appropriate class-sized logics and their relations to large cardinals. This is joint work with Trevor Wilson.



Next Week in Logic at CUNY:

- - - - Monday, Mar 11, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 11, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Otávio Bueno (Miami)
Title: Dispensing with the grounds of logical necessity

Abstract: Logical laws are typically conceived as being necessary. But in virtue of what is this the case? That is, what are the grounds of logical necessity? In this paper, I examine four different answers to this question in terms of: truth-conditions, invariance of truth-values under different interpretations, possible worlds, and brute facts. I ultimately find all of them wanting. I conclude that an alternative conception of logic that dispenses altogether with grounds of logical necessity provides a less troublesome alternative. I then indicate some of the central features of this conception.




- - - - Tuesday, Mar 12, 2024 - - - -

MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Tuesday, March 12, 1pm

Albert Visser, Utrecht University
Restricted completions

This talk reports on research in collaboration with Ali Enayat and Mateusz Łełyk.

Steffen Lempp and Dino Rossegger asked: is there a consistent completion of  that is axiomatised by sentences of bounded quantifier-alternation complexity? We show that there is no such restricted completion. We also show that, if one changes the measure of complexity to being , there is a restricted completion. Specifically, we show that the true theory of the non-negative part of  can be axiomatised by a single sentence plus a set of -sentences.

In our talk we will sketch these two answers. One of our aims is to make clear is that the negative answer for the case of quantifier-alternation complexity simply follows from Rosser's Theorem viewed from a sufficiently abstract standpoint.




- - - - Wednesday, Mar 13, 2024 - - - -



- - - - Thursday, Mar 14, 2024 - - - -



- - - - Friday, Mar 15, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 15, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Chris Lambie-Hanson, Czech Academy of Sciences


Logic Workshop
CUNY Graduate Center
Friday Mar 15, 2:00pm-3:30pm, Room 5417
Michał Godziszewski, University of Warsaw



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
Groups, Logic, and Dynamics
This is the second installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, Due to the scheduled water supply outage in the Institute next Wednesday, the seminar is cancelled next week (March 6th). Stefan's talk will take place one week later, Wednesday March 13th. I will send one more regular announcement during week before the seminar. Best, David On 29/02/2024 21:05, David Chodounsky wrote: > Dear all, > > The seminar meets on Wednesday March 6th at 11:00 in the Institute of > Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. > > > Program: Stefan Geschke -- Separating Borel chromatic numbers > > We discuss various graphs on the Cantor space and discuss the question > whether their Borel chromatic numbers can consistently be different. > > > Best, > David

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 6th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Stefan Geschke -- Separating Borel chromatic numbers We discuss various graphs on the Cantor space and discuss the question whether their Borel chromatic numbers can consistently be different. Best, David

45th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

Hello! This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Takayuki Kihara from Nagoya University. This talk is going to take place this Friday, Mar. 01, from 4pm to 5pm(UTC+8, Beijing time). 

[Title]
On the Wadge degrees of Borel partitions

[Abstract]
In descriptive set theory, there are a lot of semi-well-ordered hierarchies, such as the Borel hierarchy, the projective hierarchy, and the difference hierarchy. Under AD, their ultimate refinement is provided by the Wadge degrees, which is also semi-well-ordered.

Now, the question arises: what exactly gives rise to this semi-well-ordered structure?

Our goal is to reveal the true structure behind this semi-well-order. To achieve this, it is crucial to handle not subsets (two-valued functions) but partitions (k-valued functions). As long as we only observe two-valued functions, all dynamic mechanisms lurking behind collapse, appearing to our eyes only as a semi-well-order. By dealing with partitions, we can expose the ultimate dynamic structure that was concealed. What existed there is not a semi-well-order but rather a better quasi-order, -- a sort of transfinite "matryoshkas" of trees.

_____________________________________________________________________________________________________

Title :The 45th Nankai Logic Colloquium --Takayuki Kihara 
Time :16:00pm, Mar. 1, 2024(Beijing Time)
Zoom Number : 776 677 2207
Passcode :477893
_____________________________________________________________________

The records of past talks can be accessed at https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao




Cross-Alps Logic Seminar (speaker: Simon Henry)

Cross-Alps Logic Seminar
On Friday 01.03.2024 at 16.00 CET
Simon Henry (University of Ottawa)
will give a talk on 
Higher categorical language

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.

The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2022 'Models, Sets and Classifications'.

All the best,
Vincenzo

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 26, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, Feb 26, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Matteo Plebani (Turin).
Title: Semantic paradoxes as collective tragedies

Abstract: What does it mean to solve a paradox? A common assumption is that to solve a paradox we need to find the wrong step in a certain piece of reasoning. In this talk, I will argue while in the case of some paradoxes such an assumption might be correct, in the case of paradoxes such as the liar and Curry’s paradox it can be questioned.




- - - - Tuesday, Feb 27, 2024 - - - -

MOPA
CUNY Graduate Center
Tuesday, Feb 27, 1pm
Virtual: email Victoria Gitman (vgitman@gmail.com) for meeting id
Elliot Glazer Harvard University



Computational Logic Seminar  
Spring 2024 (online)
Tuesday, February 27, 2:00 - 4:00 PM
For a ZOOM link contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Vincent Peluce, Graduate Center
Title: What is Intuitionistic Arithmetic

Abstract:  L.E.J. Brouwer famously took the subject’s intuition of time to be foundational and from there ventured to build up mathematics. Despite being largely critical of formal methods, Brouwer valued axiomatic systems for their use in both communication and memory. Through the Dutch Mathematical Society, Gerrit Mannoury posed a challenge in 1927 to provide an axiomatization of intuitionistic arithmetic. Arend Heyting’s 1928 axiomatization was chosen as the winner and has since enjoyed the status of being the de facto formalization of intuitionistic arithmetic. We argue that axiomatizations of intuitionistic arithmetic ought to make explicit the role of the subject’s activity in the intuitionistic arithmetical process. While Heyting Arithmetic is useful when we want to contrast constructed objects with platonistic ones, Heyting Arithmetic omits the contribution of the subject and thus falls short as a response to Mannoury’s challenge. We offer our own solution, Doxastic Heyting Arithmetic, or DHA, which we contend axiomatizes Brouwerian intuitionistic arithmetic



- - - - Wednesday, Feb 28, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Astra Kolomatskaia, Stony Brook.
Date and Time:     Wednesday February 28, 2024, 7:00 - 8:30 PM. IN PERSON TALK! Room 6417
Title:     Displayed Type Theory and Semi-Simplicial Types.

Abstract: One way to think about the language of Homotopy Type Theory [HoTT], is that it enforces that anything you can say is "up to homotopy". In particular, equality proofs are not strict, but rather carry the data of a particular [class of] deformation. In HoTT, all types have the structure of an infinity groupoid, and thus the language allows for conveniently working with certain infinitary structures synthetically. However, one of the most important and long standing open problems in the field is to analytically define infinitary structures such as semi-simplicial types [i.e. semi-simplicial sets "valued in" homotopy types]. The primary difficulty with this has been that as soon as you use the equality symbol in an attempted definition of such a structure, you fall into a pit of higher coherence issues such that infinitely many layers of higher coherences, with each depending on the proofs of all of the prior ones and growing exponentially in complexity, become required. In HoTT, therefore, one comes directly face-to-face with the core problems of homotopy coherent mathematics.

In this talk, we will construct semi-simplicial types in Displayed Type Theory [dTT], a fully semantically general homotopy type theory. Many of our main results are independent of type theory and will say something new and surprising about the homotopy theoretic notion of a classifier for semi-simplicial objects.

This talk is based on joint work with Michael Shulman. Reference: https://arxiv.org/abs/2311.18781



- - - - Thursday, Feb 29, 2024 - - - -



- - - - Friday, Mar 1, 2024 - - - -

Model Theory Seminar
CUNY Graduate Center
Friday Mar 1, 12:30pm NY time, Room: 6495
Rehana Patel Wesleyan University
I will present a transfer principle in structural Ramsey theory from finite structures to ultraproducts. In joint work with Bartosova, Dzamonja and Scow, we show that under certain mild conditions and assuming CH, when a class of finite structures has finite small Ramsey degrees, the ultraproduct has finite big Ramsey degrees for internal colorings. All Ramsey-theoretic definitions will be provided, and if time permits, I will give a sketch of the proof.




Logic Workshop
CUNY Graduate Center
Friday Mar 1, 2:00pm-3:30pm, Room 5417

Alf Dolich, CUNY
Component Closed Structures on the Reals

A structure, R, expanding  is called component closed if whenever  is definable so are all of 's connected components. Two basic examples of component closed structures are  and . It turns out that these two structures are exemplary of a general phenomenon for component closed structures from a broad class of expansions of : either their definable sets are very 'tame' (as in the case of the real closed field) or they are quite 'wild' (as in the case of the real field expanded by the integers).



Next Week in Logic at CUNY:

- - - - Monday, Mar 4, 2024 - - - -

Rutgers Logic Seminar
Monday, March 4, 3:30pm, Rutgers University, Hill 705
Sean Cox, Virginia Commonwealth


Logic and Metaphysics Workshop
Date: Monday, March 4, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Elise Crull (CUNY).
Title: Declaring no dependence

Abstract: Viable fundamental ontologies require at least one suitably stable, generic-yet-toothy metaphysical dependence relation to establish fundamentality. In this talk I argue that recent experiments in quantum physics using Page-Wootters devices to model global vs. local dynamics cast serious doubt on the existence of such metaphysical dependence relations when – and arguably, inevitably within any ontological framework – physical systems serve as the relata.



- - - - Tuesday, Mar 5, 2024 - - - -

MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Tuesday, March 5, 1pm
Virtual: email Victoria Gitman (vgitman@gmail.com) for meeting id
Piotr Gruza University of Warsaw



- - - - Wednesday, Mar 6, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Jean-Pierre Marquis, Universite de Montreal.

Date and Time:     Wednesday March 6, 2024, 7:00 - 8:30 PM. IN PERSON TALK!

Title:     Hom sweet Hom: a sketch of the history of duality in category theory.


Abstract: Duality, in its various forms and roles, played a surprisingly important part in the development of category theory. In this talk, I will concentrate on the development of these forms and roles that lead to the categorical formulation of Stone-type dualities in the 1970s. I will emphasize the epistemological gain and loss along the way.




- - - - Thursday, Mar 7, 2024 - - - -



- - - - Friday, Mar 8, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 8, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Jonathan Osinski University of Hamburg



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
Groups, Logic, and Dynamics
This is the second installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 28th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Pavel Pudlák -- Colorings of $k$-sets with low discrepancy on small sets Joint result with Vojtech Rodl According to Ramsey theorem, for every $k$ and $n$, if $N$ is sufficiently large, then for every 2-coloring $\psi$ of $k$-element subsets of $[N]$ there exists a monochromatic set $S\sub[N]$ (a set such that all $k$-element subsets of $S$ have the same color given by $\psi$), $|S|=m$. The least such number is denoted by $R_k(m)$. Old results of Erd\H os, Hajnal and Rado (1965) imply that $R_k(m)\leq {\rm tw}_{k}(c m)$, where $\tw_k(x)$ is the tower function defined by ${\rm tw}_1(x)=x$ and ${\rm tw}_{i+1}(x)=2^{{\rm tw}_i(x)}$. On the other hand, these authors also showed that if $N\leq {\rm tw}_{k-1}(c'm^2)$, then there exists a coloring~$\psi$ such that there is no monochromatic $S\sub[N]$, $|S|=m$. We are interested in the question what more one can say when $N$ is smaller than ${\rm tw}_{k-1}(m)$ and $m$ is only slightly larger than $k$. We will show that, for particular values of the parameters $k,m,N$, there are colorings such that on all subsets $S$, $|S|\geq m$, the number of $k$-subsets of one color is close to the number of $k$-subsets of the other color. Best, David

44th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

Happy Chinese New Year, Nankai Logic Colloquium is resuming for the new semester!

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Clark Lyons from the University of California, Los Angeles. This talk is going to take place this Friday, Feb 23, from 9am to 10am(UTC+8, Beijing time). 

Title: Baire Measurable Matchings in Non-amenable Graphs

Abstract: Tutte's theorem provides a necessary and sufficient condition 
for a finite graph to have a perfect matching. In this talk I will 
present joint work with Kastner showing that if a locally finite Borel 
graph satisfies a strengthened form of Tutte's condition, then it has a 
perfect matching which is Baire measurable. As a consequence, the 
Schreier graph of a free action of a non-amenable group on a Polish 
space admits a Baire measurable perfect matching. This is analogous to 
the result of Csoka and Lippner on factor of IID perfect matchings for 
non-amenable Cayley graphs.

_____________________________________________________________________________________________________

Title :The 44th Nankai Logic Colloquium --Clark Lyons 
Time :9:00am, Feb. 23, 2024(Beijing Time)
Zoom Number : 776 677 2207
Passcode :477893
_____________________________________________________________________

The records of past talks can be accessed at https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao




Set theory and topology seminar 27.02.2024 Grzegorz Plebanek

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in set theory and topology (on Tuesday 27.02.2024 at 17:15 in room A.4.1 C-19  (Wrocław University of Science and Technology) the lecture:
"Aftermath of the Winter School"
will be presented by

Grzegorz Plebanek


Abstract: 
We shall discuss two problems on measures on compact spaces posed by Jiri Spurny. 

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)


About 15 minutes before the seminar we invite you for coffee and a chat to social room A.4.1.A in C-19. 


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 21st at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- Preserving independent families We will review some classical facts about the preservation of independent families and facts related to the side by side Sacks model. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 19, 2024 - - - -

Rutgers Logic Seminar
Monday, Feb 19, 3:30pm, Rutgers University, Hill 705
Artem Chernikov, Maryland
Intersecting sets in probability spaces and Shelah's classification

Abstract: For any fixed n and e > 0, given a sufficiently long sequence of events in a probability space all of measure at least e, some n of them will have a common intersection. This follows from the inclusion-exclusion principle.  A more subtle pattern: for any 0 < p < q < 1, we can't find events A_i and B_i so that the measure of A_i intersected B_j is less that p and of A_j intersected B_i is greater than q for all 1 < i < j < n, assuming n is sufficiently large. This is closely connected to a fundamental model-theoretic property of probability algebras called stability. We will discuss these and more complicated patterns that arise when our events are indexed by multiple indices. In particular, how such results are connected to higher arity generalizations of de Finetti's theorem in probability, structural Ramsey theory, hypergraph regularity in combinatorics, and model theory (no prior knowledge is expected - all of these will be introduced).




- - - - Tuesday, Feb 20, 2024 - - - -

Computational Logic Seminar  
Spring 2024 
(online)
Tuesday, February 20  

SpeakerMatteo Plebani, The University of Turin
Title: Counterpossibles in relative computability theory: a closer look
Abstract: A counterpossible is a counterfactual with an impossible antecedent, like “if zero were equal to one, two would be equal to five”. Matthias Jenny [Jenny, 2018] has argued that the following is an example of a false counterpossible:

HT If the validity problem were algorithmically solvable, then arithmetical truth would be also algorithmically decidable

As Jenny himself emphasizes, establishing that HT is a false counterpossible would be highly significant. According to the standard analysis of counterfactuals ([Lewis, 1973], [Stalnaker, 1968]) all counterpossibles are vacuously true. If HT is false, then, the standard analysis of counterfactuals is wrong. 

In this paper, we will argue that HT admits two readings, which are expressed by two different ways of formalizing HT. Under the first reading, HT is clearly a counterpossible. Under the second reading, HT is clearly false. Hence, it is possible to read HT as a counterpossible (section 2) and it is possible to read HT as a false claim (section 3). However, it is unclear that it is possible to do both things at once, i.e. interpret HT as a false counterpossible.

It can be proven that the two readings are not equivalent. The formalization expressing the first reading is a mathematical theorem, which means that under the first reading, HT is a true counterpossible. On the other hand, I will argue that under the second reading HT, while false, is best interpreted as a counterpossible with a contingent antecedent.





- - - - Wednesday, Feb 21, 2024 - - - -



- - - - Thursday, Feb 22, 2024 - - - -



- - - - Friday, Feb 23, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday Feb 23, 2:00pm-3:30pm, Room 5417
Tom Benhamou Rutgers University
Commutativity of cofinal types of ultrafilters

The Tukey order finds its origins in the concept of Moore-Smith convergence in topology, and is especially important when restricted to ultrafilters with reverse inclusion. The Tukey order of ultrafilters over  was studied intensively by Blass, Dobrinen, Isbell, Raghavan, Shelah, Todorcevic and many others, but still contains many fundamental unresolved problems. After reviewing the topological background for the Tukey order, I will present a recent development in the theory of the Tukey order restricted to ultrafilters on measurable cardinals, and explain how different the situation is when compared to ultrafilters on . Moreover, we will see an important application to the Galvin property of ultrafilters. In the second part of the talk, we will demonstrate how ideas and intuition from ultrafilters over measurable cardinals lead to new results on the Tukey order restricted to ultrafilters over . This is joint with Natasha Dobrinen.




Next Week in Logic at CUNY:

- - - - Monday, Feb 26, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, Feb 26, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Matteo Plebani (Turin).
Title: Semantic paradoxes as collective tragedies

Abstract: What does it mean to solve a paradox? A common assumption is that to solve a paradox we need to find the wrong step in a certain piece of reasoning. In this talk, I will argue while in the case of some paradoxes such an assumption might be correct, in the case of paradoxes such as the liar and Curry’s paradox it can be questioned.




- - - - Tuesday, Feb 27, 2024 - - - -

MOPA
CUNY Graduate Center
Tuesday, Feb 27, 1pm
Virtual: email Victoria Gitman (vgitman@gmail.com) for meeting id
Elliot Glazer Harvard University



- - - - Wednesday, Feb 28, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Astra Kolomatskaia, Stony Brook.
Date and Time:     Wednesday February 28, 2024, 7:00 - 8:30 PM. IN PERSON TALK! Room 6417
Title:     Displayed Type Theory and Semi-Simplicial Types.

Abstract: One way to think about the language of Homotopy Type Theory [HoTT], is that it enforces that anything you can say is "up to homotopy". In particular, equality proofs are not strict, but rather carry the data of a particular [class of] deformation. In HoTT, all types have the structure of an infinity groupoid, and thus the language allows for conveniently working with certain infinitary structures synthetically. However, one of the most important and long standing open problems in the field is to analytically define infinitary structures such as semi-simplicial types [i.e. semi-simplicial sets "valued in" homotopy types]. The primary difficulty with this has been that as soon as you use the equality symbol in an attempted definition of such a structure, you fall into a pit of higher coherence issues such that infinitely many layers of higher coherences, with each depending on the proofs of all of the prior ones and growing exponentially in complexity, become required. In HoTT, therefore, one comes directly face-to-face with the core problems of homotopy coherent mathematics.

  • In this talk, we will construct semi-simplicial types in Displayed Type Theory [dTT], a fully semantically general homotopy type theory. Many of our main results are independent of type theory and will say something new and surprising about the homotopy theoretic notion of a classifier for semi-simplicial objects.

    This talk is based on joint work with Michael Shulman. Reference: https://arxiv.org/abs/2311.18781



- - - - Thursday, Feb 29, 2024 - - - -



- - - - Friday, Mar 1, 2024 - - - -

Model Theory Seminar
CUNY Graduate Center
Friday Mar 1, 12:30pm NY time, Room: 6495
Rehana Patel Wesleyan University


Logic Workshop
CUNY Graduate Center
Friday Mar 1, 2:00pm-3:30pm, Room 5417

Alf Dolich, CUNY
Component Closed Structures on the Reals

A structure, R, expanding  is called component closed if whenever  is definable so are all of 's connected components. Two basic examples of component closed structures are  and . It turns out that these two structures are exemplary of a general phenomenon for component closed structures from a broad class of expansions of : either their definable sets are very 'tame' (as in the case of the real closed field) or they are quite 'wild' (as in the case of the real field expanded by the integers).





- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
Groups, Logic, and Dynamics
This is the second installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Logic Seminar Wed 21.02.2024 17:00 hrs at NUS by Neil Barton

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 21 February 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Speaker: Neil Barton Title: Title: Potentialist Sets, Intensions, and Non-Classicality A popular view in the philosophy of set theory is that of *potentialism*: the position that the set-theoretic universe unfolds as more sets come into existence or become accessible to us. This often gets formalised using *modal logic*, but there is always a question of how to move to *non-modal* theories. In this latter regard, a difficult question for the potentialist is to explain how *intensional entities* (entities individuated by an application condition rather than an extension) behave, and in particular what logic governs them. This talk will discuss some work in progress on this issue. We'll see how to motivate acceptance of different propositional logics for different flavours of potentialism, and discuss the prospects for proving results about the kinds of first-order theories validated. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 12, 2024 - - - -

Rutgers Logic Seminar
Monday, Feb 12, 3:30pm, Rutgers University, Hill 705
Gunter Fuchs, CUNY
Blurry HOD: a hierarchy of inner models

For a cardinal $\kappa\ge 2$, one can weaken the classical concept "x is ordinal definable" (i.e., x is the unique object satisfying some condition involving ordinal parameters) to "x is <$\kappa$-blurrily ordinal definable," meaning that x is one of fewer than $\kappa$ many objects satisfying some condition involving ordinal parameters. By considering the hereditary version of this, one naturally arrives at the inner model <$\kappa$-HOD, the class of all hereditarily <$\kappa$-blurrily ordinal definable sets. In ZFC, by varying $\kappa$, one obtains a hierarchy of inner models spanning the entire spectrum from HOD to V. Those stages in the hierarchy where something new is added I call leaps.

I will give an overview of what is known about this hierarchy: ZFC-provable facts regarding the relationships between the stages of the hierarchy and the basic structure of leaps, and consistency results on leap constellations, including consistency strength determinations.




- - - - Tuesday, Feb 13, 2024 - - - -

MOPA
CUNY Graduate Center
Tuesday, Feb 13, 1pm
Virtual: email Victoria Gitman (vgitman@gmail.com) for meeting id
Dino Rossegger TU Wien
The Borel complexity of first-order theories

The Borel hierarchy gives a robust way to stratify the complexity of sets of countable structures and is intimately tied with definability in infinitary logic via the Lopez-Escobar theorem. However, what happens with sets axiomatizable in finitary first-order logic, such as the set of structures satisfying a given finitary first-order theory T? Is the complexity of the set of T's models in any way related to the quantifier complexity of the sentences axiomatizing it? In particular, if a theory T is not axiomatizable by a set of sentences of bounded quantifier complexity, can the set of models of T still be at a finite level of the Borel hierarchy?

In this talk, we will present results concerning these questions:

In joint work with Andrews, Gonzalez, Lempp, and Zhu we show that the set of models of a theory T is -complete if and only if T does not have an axiomatization by sentences of bounded quantifier complexity, answering the last question in the negative. We also characterize the Borel complexity of the set of models of complete theories in terms of their finitary axiomatizations. Our results suggest that infinitary logic does not provide any efficacy when defining first-order properties, a phenomenon already observed by Wadge and Keisler and, recently, rediscovered by Harrison-Trainor and Kretschmer using different techniques.

Combining our results with recent results by Enayat and Visser, we obtain that a large class of theories studied in the foundations of mathematics, sequential theories, have a maximal complicated set of models.


Computational Logic Seminar  
Spring 2024 
(online)
Tuesday, February 13  
Time 2:00 - 4:00 PM 
For a zoom link contact Sergei Artemov (
SArtemov@gc.cuny.edu)
Speaker: Melvin Fitting, CUNY Graduate Center
Title: About Semantic Tableaus

Abstract:I will sketch the basics of tableau proof systems, beginning with those for classical propositional logic.  Then I will move to intuitionistic tableaus and modal tableaus (more than one kind of tableau system).  Finally I’ll say something about quantifiers.  Slides exist for the beginning part of the talk.  When they run out I’ll work on the Zoom equivalent of a blackboard.




- - - - Wednesday, Feb 14, 2024 - - - -



- - - - Thursday, Feb 15, 2024 - - - -



- - - - Friday, Feb 16, 2024 - - - -

Computability Seminar
CUNY Graduate Center
Friday, Feb 16, 10:30-11:30am NY time, Room: 3305
Speaker: Andrea Volpi, University of Udine

Largeness notions

Finite Ramsey Theorem states that fixed , there exists  such that for each coloring of  with  colors, there is a homogeneous subset  of  of cardinality at least . Starting with the celebrated Paris-Harrington theorem, many Ramsey-like results have been studied using different largeness notions rather than the cardinality. I will introduce the largeness notion defined by Ketonen and Solovay based on fundamental sequences of ordinals. Then I will describe an alternative and more flexible largeness notion using blocks and barriers. If time allows, I will talk about how the latter can be used to study a more general Ramsey-like result.


Logic Workshop
CUNY Graduate Center
Friday Feb 16, 2:00pm-3:30pm, Room 5417
Damir Dzhafarov, University of Connecticut

The Ginsburg-Sands theorem and computability

In their 1979 paper `Minimal Infinite Topological Spaces,’ Ginsburg and Sands proved that every infinite topological space has an infinite subspace homeomorphic to exactly one of the following five topologies on : indiscrete, discrete, initial segment, final segment, and cofinite. The proof, while nonconstructive, features an interesting application of Ramsey's theorem for pairs (). We analyze this principle in computability theory and reverse mathematics, using Dorais's formalization of CSC spaces. Among our results are that the Ginsburg-Sands theorem for CSC spaces is equivalent to  while for Hausdorff spaces it is provable in . Furthermore, if we enrich a CSC space by adding the closure operator on points, then the Ginsburg-Sands theorem turns out to be equivalent to the Chain-Antichain Principle (). The most surprising case is that of the Ginsburg-Sands theorem restricted to  spaces. Here, we show that the principle lies strictly between  and , yielding perhaps the first natural theorem of ordinary mathematics (i.e., conceived outside of logic) to occupy this interval. I will discuss the proofs of both the implications and separations, which feature several novel combinatorial elements, and survey a new class of purely combinatorial principles below  and not implied by  revealed by our investigation. This is joint work with Heidi Benham, Andrew DeLapo, Reed Solomon, and Java Darleen Villano.




Next Week in Logic at CUNY:

- - - - Monday, Feb 19, 2024 - - - -



- - - - Tuesday, Feb 20, 2024 - - - -



- - - - Wednesday, Feb 21, 2024 - - - -



- - - - Thursday, Feb 22, 2024 - - - -



- - - - Friday, Feb 23, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday Feb 23, 2:00pm-3:30pm, Room 5417
Tom Benhamou Rutgers University



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
Groups, Logic, and Dynamics
This is the second installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 14th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet determined, the backup option is Chris and/or Šárka talking about Kurepa trees. Best, David

Logic Seminar Talk 7 February 2024 17:00 hrs by Alexander Rabinovich at NUS

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 7 February 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Speaker: Alexander Rabinovich, Tel Aviv University Title: The Church Synthesis Problem over Continuous Time Abstract: Church's Problem asks for the construction of a procedure which, given a logical specification S(I,O) between input-strings I and output-strings O, determines whether there exists an operator F that implements the specification in the sense that S(I,F(I)) holds for all inputs I. Buechi and Landweber gave a procedure to solve Church's problem for MSO specifications and operators computable by finite-state automata. We investigate a generalization of the Church synthesis problem to the continuous time of the non-negative reals. It turns out that in the continuous time there are phenomena which are very different from the canonical discrete time domain of the natural numbers. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 5, 2024 - - - -

Rutgers Logic Seminar
Monday, Feb 5, 3:30pm, Rutgers University, Hill 705
Filippo Calderoni, Rutgers
The L-space conjecture and descriptive set theory


Logic and Metaphysics Workshop
Date: Monday, Feb 5, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Roman Kossak, CUNY

TitleSome model theory for axiomatic theories of truth

 

AbstractTarski’s arithmetic is the complete theory of (N,+,x,Tr), where (N,+,x) is the standard model of arithmetic and Tr is the set of Gödel numbers of all true arithmetic sentences. An axiomatic theory of truth is an axiomatic subtheory of Tarski’s arithmetic. If (M,+,x,T) is a model of an axiomatic theory of truth, then we call T a truth class. In 1981, Kotlarski, Krajewski, and Lachlan proved that every completion of Peano’s arithmetic has a model that is expandable to a model  with a truth class T that satisfies all biconditionals in Tarski’s definition of truth formalized in PA. If T is such a truth class, it assigns truth values to all sentences in the sense of M, standard and nonstandard. The proof showed  that such truth classes can be quite pathological. For example, they may declare true some infinite disjunctions of the single sentence (0=1). In 2018, Enayat and Visser gave  a much simplified model-theoretic proof, which opened the door for further investigations of nonstandard truths, and many interesting new results by many authors appeared. I will survey some of them, concentrating on their model-theoretic content.






- - - - Tuesday, Feb 6, 2024 - - - -



- - - - Wednesday, Feb 7, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Saeed Salehi, Univeristy of Tarbiz.

Date and Time:     Wednesday February 7, 2024, 11:00AM - 12:00 NOON. NOTICE SPECIAL TIME!!! ZOOM TALK!!! (see website for zoom link)

Title:     On Chaitin's two HP's: (1) Heuristic Principle and (2) Halting Probability.


Abstract: Two important achievements of Chaitin will be investigated: the Omega number, which is claimed to be the halting probability of input-free programs, and the heuristic principle, which is claimed to hold for program-size complexity. Chaitin's heuristic principle says that the theories cannot prove the heavier sentences; the sentences and the theories were supposedly weighed by various computational complexities, which all turned out to be wrong or incomplete. In this talk, we will introduce a weighting that is not based on any computational complexity but on the provability power of the theories, for which Chaitin's heuristic principle holds true. Also, we will show that the Omega number is not equal to the halting probability of the input-free programs and will suggest some methods for calculating this probability, if any.




- - - - Thursday, Feb 8, 2024 - - - -



- - - - Friday, Feb 9, 2024 - - - -

Computability Seminar
CUNY Graduate Center
Friday, Feb 9, 10:30-11:30am NY time, Room: 3305
Title: Computability of equilibrium measures
Speaker:  Emma Dinowitz, Grad Center



Set Theory Seminar
CUNY Graduate Center
Friday, Feb 9, 12:30pm NY time, Room: 6494
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Tom Benhamou Rutgers University

Tukey-top ultrafilters under UA

In the first part of the talk, we will provide some background and motivation to study the Glavin property. In particular, we will present a recently discovered connection between the Galvin property and the Tukey order on ultrafilters. This is a joint result with Natasha Dobrinen. In the second part, we will introduce several diamond-like principles for ultrafilters, and prove some relations with the Galvin property. Finally, we use the Ultrapower Axiom to characterize the Galvin property in the known canonical inner models. The second and third part is joint work with Gabriel Goldberg.




Logic Workshop
CUNY Graduate Center
Friday Feb 9, 2:00pm-3:30pm, Room 5417
Russell Miller CUNY

Properties of Generic Algebraic Fields

The algebraic field extensions of the rational numbers  – equivalently, the subfields of the algebraic closure  – naturally form a topological space homeomorphic to Cantor space. Consequently, one can speak of 'large' collections of such fields, in the sense of Baire category: collections that are comeager in the space. Under a standard definition, the 1-generic fields form a comeager set in this space. Therefore, one may think of a property common to all 1-generic fields as a property that one might reasonably expect to be true of an arbitrarily chosen algebraic field.

We will present joint work with Eisenträger, Springer, and Westrick that proves several intriguing properties to be true of all 1-generic fields . First, in every such , both the subring  of the integers and the subring  of the algebraic integers of  cannot be defined within  by an existential formula, nor by a universal formula. (Subsequent work by Dittman and Fehm has shown that in fact these subrings are completely undefinable in these fields.) Next, for every presentation of every such , the root set

is always of low Turing degree relative to that presentation, but is essentially always undecidable relative to the presentation. Moreover, the set known as Hilbert's Tenth Problem for ,

is exactly as difficult as , which is its restriction to single-variable polynomials. Finally, even the question of having infinitely many solutions,

is only as difficult as . These results are proven by using a forcing notion on the fields and showing that it is decidable whether or not a given condition forces a given polynomial to have a root, or to have infinitely many roots.




Next Week in Logic at CUNY:

- - - - Monday, Feb 12, 2024 - - - -

Rutgers Logic Seminar
Monday, Feb 12, 3:30pm, Rutgers University, Hill 705
Gunter Fuchs, CUNY



- - - - Tuesday, Feb 13, 2024 - - - -

MOPA
CUNY Graduate Center
Tuesday, Feb 13, 1pm
Virtual: email Victoria Gitman (vgitman@gmail.com) for meeting id
Dino Rossegger TU Wien
The Borel complexity of first-order theories

The Borel hierarchy gives a robust way to stratify the complexity of sets of countable structures and is intimately tied with definability in infinitary logic via the Lopez-Escobar theorem. However, what happens with sets axiomatizable in finitary first-order logic, such as the set of structures satisfying a given finitary first-order theory T? Is the complexity of the set of T's models in any way related to the quantifier complexity of the sentences axiomatizing it? In particular, if a theory T is not axiomatizable by a set of sentences of bounded quantifier complexity, can the set of models of T still be at a finite level of the Borel hierarchy?

In this talk, we will present results concerning these questions:

In joint work with Andrews, Gonzalez, Lempp, and Zhu we show that the set of models of a theory T is -complete if and only if T does not have an axiomatization by sentences of bounded quantifier complexity, answering the last question in the negative. We also characterize the Borel complexity of the set of models of complete theories in terms of their finitary axiomatizations. Our results suggest that infinitary logic does not provide any efficacy when defining first-order properties, a phenomenon already observed by Wadge and Keisler and, recently, rediscovered by Harrison-Trainor and Kretschmer using different techniques.

Combining our results with recent results by Enayat and Visser, we obtain that a large class of theories studied in the foundations of mathematics, sequential theories, have a maximal complicated set of models.




- - - - Wednesday, Feb 14, 2024 - - - -



- - - - Thursday, Feb 15, 2024 - - - -



- - - - Friday, Feb 16, 2024 - - - -

Computability Seminar
CUNY Graduate Center
Friday, Feb 16, 10:30-11:30am NY time, Room: 3305
Speaker: Andrea Volpi, University of Udine

Largeness notions

Finite Ramsey Theorem states that fixed , there exists  such that for each coloring of  with  colors, there is a homogeneous subset  of  of cardinality at least . Starting with the celebrated Paris-Harrington theorem, many Ramsey-like results have been studied using different largeness notions rather than the cardinality. I will introduce the largeness notion defined by Ketonen and Solovay based on fundamental sequences of ordinals. Then I will describe an alternative and more flexible largeness notion using blocks and barriers. If time allows, I will talk about how the latter can be used to study a more general Ramsey-like result.


Logic Workshop
CUNY Graduate Center
Friday Feb 16, 2:00pm-3:30pm, Room 5417
Damir Dzhafarov, University of Connecticut


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, There is no seminar on Wednesday next week. However, we have Andy Zucker visiting the Institute during the next week, Andy will give a talk at the Set Theory and Analysis seminar on Tuesday morning 10:00--11:30, Institute of Mathematics CAS, Zitna 25, konirna room, ground floor, front building. Program: Andy Zucker -- Ultracoproducts and weak containment for flows of topological groups We develop the theory of ultracoproducts and weak containment for flows of arbitrary topological groups. This provides a nice complement to corresponding theories for p.m.p. actions and unitary representations of locally compact groups. For the class of locally Roelcke precompact groups, the theory is especially rich, allowing us to define for certain families of G-flows a suitable compact space of weak types. When G is locally compact, all G-flows belong to one such family, yielding a single compact space describing all weak types of G-flows. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Jan 29, 2024 - - - -

Rutgers Logic Seminar
Monday, Jan 29, 3:30pm, Rutgers University, Hill 705
Jenna Zomback, Maryland
Boundary actions of free semigroups




- - - - Tuesday, Jan 30, 2024 - - - -



- - - - Wednesday, Jan 31, 2024 - - - -



- - - - Thursday, Feb 1, 2024 - - - -



- - - - Friday, Feb 2, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 2, 12:30pm NY time, Room: 6494
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Dima Sinapova Rutgers University




Logic Workshop
CUNY Graduate Center
Friday Feb 2, 2:00pm-3:30pm, Room 5417
Gunter Fuchs CUNY
TBA



Next Week in Logic at CUNY:

- - - - Monday, Feb 5, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, Feb 5, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395

TitleSome model theory for axiomatic theories of truth

 

AbstractTarski’s arithmetic is the complete theory of (N,+,x,Tr), where (N,+,x) is the standard model of arithmetic and Tr is the set of Gödel numbers of all true arithmetic sentences. An axiomatic theory of truth is an axiomatic subtheory of Tarski’s arithmetic. If (M,+,x,T) is a model of an axiomatic theory of truth, then we call T a truth class. In 1981, Kotlarski, Krajewski, and Lachlan proved that every completion of Peano’s arithmetic has a model that is expandable to a model  with a truth class T that satisfies all biconditionals in Tarski’s definition of truth formalized in PA. If T is such a truth class, it assigns truth values to all sentences in the sense of M, standard and nonstandard. The proof showed  that such truth classes can be quite pathological. For example, they may declare true some infinite disjunctions of the single sentence (0=1). In 2018, Enayat and Visser gave  a much simplified model-theoretic proof, which opened the door for further investigations of nonstandard truths, and many interesting new results by many authors appeared. I will survey some of them, concentrating on their model-theoretic content.






- - - - Tuesday, Feb 6, 2024 - - - -



- - - - Wednesday, Feb 7, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Saeed Salehi, Univeristy of Tarbiz.

Date and Time:     Wednesday February 7, 2024, 11:00AM - 12:00 NOON. NOTICE SPECIAL TIME!!! ZOOM TALK!!! (see website for zoom link)

Title:     On Chaitin's two HP's: (1) Heuristic Principle and (2) Halting Probability.


Abstract: Two important achievements of Chaitin will be investigated: the Omega number, which is claimed to be the halting probability of input-free programs, and the heuristic principle, which is claimed to hold for program-size complexity. Chaitin's heuristic principle says that the theories cannot prove the heavier sentences; the sentences and the theories were supposedly weighed by various computational complexities, which all turned out to be wrong or incomplete. In this talk, we will introduce a weighting that is not based on any computational complexity but on the provability power of the theories, for which Chaitin's heuristic principle holds true. Also, we will show that the Omega number is not equal to the halting probability of the input-free programs and will suggest some methods for calculating this probability, if any.




- - - - Thursday, Feb 8, 2024 - - - -



- - - - Friday, Feb 9, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 9, 12:30pm NY time, Room: 6494
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Tom Benhamou Rutgers University




Logic Workshop
CUNY Graduate Center
Friday Feb 9, 2:00pm-3:30pm, Room 5417
Russell Miller CUNY
TBA


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

43rd Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Alexander S. Kechris from the California Institute of Technology. This talk is going to take place this Friday, Jan 26, from 9am to 10am(UTC+8, Beijing time). 



Title: The compact action realization problem
Abstract:
In this talk I will discuss realizations of countable Borel equivalence relations by continuous actions of countable groups, focusing in particular on the problem of realization by continuous actions on compact spaces and more specifically subshifts. This also leads to considering a natural universal space for actions and equivalence relations via subshifts and the study of the descriptive and topological properties in this universal space of various classes of countable Borel equivalence relations, especially the hyperfinite ones.
_____________________________________________________________________________________________________ 
Title :The 43rd Nankai Logic Colloquium --Alexander S. Kechris
Time :9:00am, Jan. 26, 2024(Beijing Time)
Zoom Number : 776 677 2207
Passcode :477893
Link :https://us02web.zoom.us/j/7766772207?pwd=eUtGVzBMdExhZWl6ZllRRFZaVnU2dz09&omn=85249314599
_____________________________________________________________________

The records of past talks can be accessed at https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao




7th Workshop on Generalised Baire Spaces

Conference
This is the seventh in a series of workshops that have taken place from 2014. These workshops aim to connect researchers working in the descriptive set theory of Baire and Cantor spaces of functions on uncountable cardinals and its connections with infinite combinatorics and model theory. The upcoming workshop features several well-known speakers and aims to connect this area with large cardinals. There will be ample time for discussion and collaboration.
Link to more info

Invitation to Logic Seminar 31 January 2024 17:00 hrs at NUS by Yu Liang

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 31 January 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Speaker: Yu Liang Title: Some Applications of Recursion Theory to Geometric Measure Theory Abstract: Geometric measure theory relates effectivity notions to dimensions and measures like the Hausdorff dimension. The talk gives further links to the Axiom of Determinacy over ZF (it is not consistent with ZFC) and how these influence the geometry of the finite-dimensional Euclidian Space and its subsets. The talk explains the theorems of Besicovitch and Davis, of father and son Lutz and of Slaman; these theorems are related to recent results in the field including those by the speaker. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

The Spring 2024 semester starts this Thursday, 1/25 -- welcome back!  While many seminars will not meet this week, please take note of the special memorial event for Martin Davis on Friday 1/26.

Best,
Jonas

This Week in Logic at CUNY:

- - - - Monday, Jan 22, 2024 - - - -

Rutgers Logic Seminar
Monday, Dec 11, 3:30pm, Rutgers University, Hill 705
Will Boney (Texas State)
Building generalized indiscernibles in nonelementary classes with set theory



- - - - Tuesday, Jan 23, 2024 - - - -



- - - - Wednesday, Jan 24, 2024 - - - -



- - - - Thursday, Jan 25, 2024 - - - -



- - - - Friday, Jan 26, 2024 - - - -

Memorial Lectures for Martin Davis
January 26, 2024
Courant Institute

All are welcome to attend this special event in memory of Professor Martin Davis.
There will be three lectures on his work from 1:00 - 2:30 pm, a memorial for Martin
and Virginia Davis from 2:45 - 3:45 pm, and a reception afterwards from 4-6 pm.
Preregistration is requested, ideally by January 15, using the website
https://cims.nyu.edu/dynamic/conferences/davis-memorial/




Next Week in Logic at CUNY:

- - - - Monday, Jan 29, 2024 - - - -



- - - - Tuesday, Jan 30, 2024 - - - -



- - - - Wednesday, Jan 31, 2024 - - - -



- - - - Thursday, Feb 1, 2024 - - - -



- - - - Friday, Feb 2, 2024 - - - -




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 24th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There will be no seminar on Wednesday January 31st (Winter School) and probably no seminar on February 7th (workshop in Bristol). Program January 24th: Cesar Corral -- MAD families with pseudocompact hyperspaces Pseudocompactness of hyperspaces was studied by J. Ginsburg, who asked whether there is a relationship between the pseudocompactness of X^\omega and the hyperspace exp(X) for a topological space X. For an almost disjoint family \mathcal{A}, maximality is equivalent to the pseudocompactness of \Psi(\mathcal{A}) and that of \Psi(\mathcal{A})^\omega. Hence J. Cao and T. Nogura asked whether some/every MAD family has a pseudocompact hyperspace. Recently, the statement that every MAD family has a pseudocompact hyperspace was proved to be equivalent to the Novak or Baire number \mathfrak{n} being greater than \mathfrak{c}, however, not much more is known about the existence of MAD families with pseudocompact hyperspace. We will address this problem by showing many models and cardinal invariant assumptions that imply the existence of MAD families with pseudocompact hyperspace. Best, David

Second Wrocław Logic Conference, Wrocław, 31 May to 2 Jun, 2024

Conference
SECOND WROCLAW LOGIC CONFERENCE will take place 31st May - 2nd June 2024, in Wrocław, Poland. The website of the conference: https://prac.im.pwr.edu.pl/~twowlc/ There is no conference fee. There will be two special lectures during the conference: * Mostowski lecture, by Stevo Todorcevic, * Ryll-Nardzewski lecture, by Jan van Mill. Invited speakers: Monroe Eskew (KGRC) Rafal Filipow, University of Gdańsk Takehiko Gappo, TU Wien Martin Goldstern, TU Wien Eliza Jabłońska, AGH Ziemowit Kostana, University of Warsaw and Bar-Ilan University Andrzej Kucharski, University of Silesia Aleksandra Kwiatkowska, University of Wrocław & WWU Munster Andreas Lietz, University of Munster Matteo Viale, University of Torino Zoltán Vidnyánszky, Eotvos University Bartosz Wcisło, University of Gdańsk The conference is organized by Politechnika Wrocławska and Uniwersytet Wrocławski. This is a continuation of First Gdansk Logic Conference. Scientific Committee: Arturo Martinez-Celis (Uniwersytet Wrocławski) Grigor Sargsyan (Polish Academy of Sciences) Szymon Żeberski (Politechnika Wrocławska) Organizing Committee: Wrocław Set Theory Group & Grigor Sargsyan
Link to more info

Set Theory and Topology Seminar 23.01.2024 Łukasz Mazurkiewicz

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 23.01.2024 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Analytic families of trees"

will be presented by

Łukasz Mazurkiewicz


Abstract.


Every tree can be seen as a point in a space P(2^<\omega) or P(\omega^<\omega). Therefore, families of trees are subsets of these "incarnations" of Cantor space and, as such, can be analyzed from the perspective of descriptive complexity. In this talk I would like to explore some classical families of trees with some focus put on the ones, which are analytic complete.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Urgent Announcement of Nankai Logic Colloquium: change to Voov (Tencent meeting)

Nankai Logic Colloquium

Hello everyone,

Sorry, we have changed the meeting software to Voov (Tencent meeting) because the our Zoom account has been banned. 

Please download Voov (Tencent meeting) from the following link:

https://voovmeeting.com/download-center.html?from=1002

the attachment is the Manual for using Voov (Tencent meeting)

_____________________________________________________________________________________________________

Title :The 42nd Nankai Logic Colloquium --Gianluca Paolini
Time :16:00pm, Jan. 19, 2024(Beijing Time)
Voov (Tencent meeting) Number : 370 658 815
Passcode : 123456
_____________________________________________________________________

Best Wishes,

Ming Xiao







Set Theory in the United Kingdom, London, February 15, 2024

Conference
You are invited to attend (or zoom-into) STUK 12, Set Theory in the United Kingdom. The meeting will take place on the campus of UCL on February 15, 2024, from 11am-6pm and will be broadcast via zoom. https://www.dpmms.cam.ac.uk/~dbl25/STUK/ Invited speakers will include: Shaun Allison Raiean Banerjee Martina Ianella The scientific organizers are Benedikt Loewe and Andrew Brooke-Taylor. The local organizer is Samuel Coskey.
Link to more info

42nd Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Gianluca Paolini from the University of Turin. This talk is going to take place this Friday, Jan 19, from 4pm to 5pm(UTC+8, Beijing time). 

Title: The Isomorphism Problem for Oligomorphic Groups with Weak Elimination of Imaginaries

Abstract: In Nies et al. [JML 22 (2022)] it was asked if equality on the reals is sharp as a lower bound for the complexity of topological isomorphism between oligomorphic groups. We prove that under the assumption of weak elimination of imaginaries this is indeed the case. Our methods are model theoretic and they also have applications on the classical problem of reconstruction of isomorphisms of permutation groups from (topological) isomorphisms of automorphisms groups. As a concrete application, we give an explicit description of Aut(GL(V)) for any vector space V of dimension \aleph_0 over a finite field, in affinity with the  classical description for finite dimensional spaces due to Schreier and van der Waerden.

_____________________________________________________________________________________________________
Title :The 42nd Nankai Logic Colloquium --Gianluca Polini
Time :16:00pm, Jan. 19, 2024(Beijing Time)
Zoom Number : 708 354 1963
Passcode : 477893

_____________________________________________________________________

The records of past talks can be accessed at https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao


Cross-Alps Logic Seminar for World Logic Day (speaker: Charles Steinhorn)

Cross-Alps Logic Seminar

On Friday 19.01.2023 at 16:00

on the occasion of World Logic Day 2024, a special session of the Cross-Alps Logic Seminars will take place, with special guest
Charles Steinhorn (Vassar College)
who will give a talk on
O-minimality as a framework for tame mathematical economics

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2022 'Models, sets and classification'.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 17th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Indecomposable ultrafilters and the Proper Forcing Axiom A common heuristic in the study of forcing axioms and compactness principles is the following: in models of strong forcing axioms, such as PFA, the cardinal omega_2 behaves in many ways like a strongly compact or supercompact cardinal. For example, classical results in the study of large cardinals imply that the Singular Cardinal Hypothesis holds, and square principles fail, above a strongly compact cardinal. Much later, both of these conclusions were also shown to follow from the Proper Forcing Axiom. In this talk, we present a very recent result in this vein. We will prove that, if PFA holds and kappa is a cardinal carrying a uniform indecomposable ultrafilter, then kappa is either measurable or a countable limit of measurable cardinals, providing an analogue of a recent result of Goldberg establishing the same conclusion above a strongly compact cardinal. This is joint work with Assaf Rinot and Jing Zhang. Best, David

Logic Seminar at NUS Wed 17.01.2024 17:00 hrs by Tatsuta Makoto

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 17 January 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Speaker: Tatsuta Makoto Title: Brotherston's Conjecture: Equivalence of Inductive Definitions and Cyclic Proofs URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html An inductive definition is a way to define a predicate by an expression which may contain the predicate itself. The predicate is interpreted by the least fixed point of the defining equation. Inductive definitions are important in computer science, since they can define useful recursive data structures such as lists and trees. Inductive definitions are important also in mathematical logic, since they increase the proof theoretic strength. Martin-Loef's system of inductive definitions given in 1971 is one of the most popular system of inductive definitions. In 2006 Brotherston proposed an alternative formalization of inductive definitions, called a cyclic proof system. In general, for proof search, a cyclic proof system can find an induction formula in a more efficient way than Martin-Loef's system, since a cyclic proof system does not have to choose fixed induction formulas in advance. The equivalence of the provability of Martin-Loef's system for inductive definitions and that of the cyclic proof system was conjectured in 2006. The speaker and Berardi solved it in 2017. This talk will explain this problem.

41st Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Felipe Garcia-Ramos from Jagiellonian University. This talk is going to take place this Friday, Jan 12, from 4pm to 5pm(UTC+8, Beijing time). 


Title: Local entropy theory and descriptive complexity. 

Abstract: We will discuss the descriptive complexity of families of dynamical systems that appear in the context of local entropy theory, such as completely positive entropy, uniform positive entropy, and completely positive mean dimension. 

The talk will contain joint work with Udayan Darji and joint work with Yonatan Gutman. 
_____________________________________________________________________________________________________ 
Title :The 41st Nankai Logic Colloquium --Felipe Garcia-Ramos
Time :16:00pm, Jan. 12, 2024(Beijing Time)
Zoom Number : 708 354 1963
Passcode : 477893
Link :https://zoom.us/j/7083541963?pwd=cEcxRUgzNEtaWXJMeGszU2NCclVLZz09&omn=93150685735
_____________________________________________________________________

The records of past talks can be accessed at https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao




KGRC Talks - January 8-12

Kurt Godel Research Center
The KGRC welcomes as guest: Aleksander Cieślak (host: Damian Sobota) visits January 8-12, 2024. * * * * * * * * * The KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) SET THEORY SEMINAR, Kolingasse 14-16, 1090, 1st floor, SR 10, TUESDAY, January 9, 3:00pm - 4:30pm, hybrid mode. (Please note the unusual date and time!) "Cofinalities of tree ideals" A. Cieślak (Wrocław U of Technology, PL) If $\mathcal{T}$ is a collection of trees on $\omega^\omega$, then we define the tree ideal $t_0$ as a collection of these $X\subset \omega^\omega$ such that each $T\in\mathcal{T}$ has a subtree $S\in\mathcal{T}$ which shares no branches with $X$. We will be interested in the cofinalities of tree ideals. Building on the work of Brendle, Khomskii, and Wohofsky, we will analyse the condition called "Incompatibility Shrinking Property", which implies that $cof(t_0)>2^\omega$. We will investigate under which assumptions this property is satisfied for two types of trees. These types are Laver and Miller trees which split positively according to some fixed ideal on $\omega$. Joint work with Arturo Martinez Celis. Zoom: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * SET THEORY SEMINAR, Kolingasse 14-16, 1090, 1st floor, SR 10, Thursday, January 11, 11:30am - 1:00pm, hybrid mode. "Forcing techniques for Cichoń's Maximum: FS iterations with measures and ultrafilters on the natural numbers" D. A. Mejía (Shizuoka U, JP) Mini-course (30.11.2023-25.01.2024, 6 lectures) - 4th lecture: We complete the proof of the consistency of the constellation for the left side of Cichoń's diagram by showing how to preserve a strong witness for the unbounding number. However, this requires a modification of the iteration, and a new theory of iterations with measures and ultrafilters. Zoom: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * LOGIC COLlOQUIUM, Faculty of Mathematcs/KGRC, Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, January 11, 3:00pm - 3:50pm, hybrid mode. "The Model Theoretic Covering Reflection Property" A. Lietz (TU Wien) The Covering Reflection Property holds at a cardinal $\kappa$ if for every first order structure $\mathcal B$ in a countable language, there is some $\mathcal A$ of size $<\kappa$ so that $\mathcal B$ can be covered with the ranges of elementary embeddings $j:\mathcal A\rightarrow \mathcal B$. That is, for every $b\in\mathcal B$, there is some $a\in\mathcal A$ and an elementary embedding $j:\mathcal A\rightarrow\mathcal B$ with $j(a)=b$. We discuss this property and isolate a new large cardinal notion strictly between almost huge and huge cardinals and show that the least cardinal exhibiting the Covering Reflection Property is exactly the least such large cardinal. Moreover, there is a natural correspondence between such large cardinals and strong forms of the Covering Reflection Property. This is joint work with Joel D. Hamkins, Nai-Chung Hou and Farmer Schlutzenberg. Zoom: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. -- Mag. Petra Czarnecki de Czarnce-Chalupa Institute of Mathematics (Kurt Goedel Research Center) University of Vienna Kolingasse 14-16, #7.48 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

set theory and topology seminar 9.01.2024 Piotr Borodulin-Nadzieja

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 9.01.2024 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Fams on omega"

will be presented by

Piotr Borodulin-Nadzieja


Abstract.

I will review some recent results about finitely additive measures on omega. In particular, I will talk about some new examples of such measures, motivated by the problem if there is a P-measure in the Silver model. Joint work with Jonathan Cancino and Adam Morawski.


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 10th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Matteo Casarosa -- Nonvanishing derived limits and (generalized) cardinal characteristics Combinatorial set theory has long proven useful in dealing with the so-called derived limits. These functors in turn are related to several problems in algebraic topology, such as the additivity of Strong Homology. Set-theoretic methods have yielded both vanishing and nonvanishing consistency results for these functors when computed on certain inverse systems of abelian groups indexed either on the ordinals or the (generalized) Baire space. In the second case, nonvanishing results have so far assumed the existence of a scale (i.e. a linear cofinal subset in the mod finite quasi-order). In this presentation, we discuss some recent developments in the case where such a set does not exist, including some work in progress with Jeffrey Bergfalk. Best, David

40th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Steve Jackson from the University of North Texas. This talk is going to take place this Friday, Jan 05, from 4pm to 5pm(UTC+8, Beijing time). 

Title: Forcing, hyperaperiodicity, and marker techniques in Borel equivalence relations. 

Abstract: We will survey some of the useful techniques that have developed for the study of continuous and Borel actions of countable groups. These include hyperaperiodicity, forcing methods, and various marker techniques. We will present some previous results which use these techniques and also present some more recent results along with some currently open problems. For example, using some of the new methods we can show that there is no continuous k-line section or even k-treeing for the free part of the shift action of Z^2. We also present some results concerning finite asymptotic dimension for equivalence relations. 
_____________________________________________________________________________________________________

Title :The 40th Nankai Logic Colloquium --Steve Jackson
Time :16:00pm, Jan. 5, 2024(Beijing Time)
Zoom Number : 393 758 7647
Passcode : 055758
Link :https://us06web.zoom.us/j/3937587647?pwd=RdX4CjblPBY3xABriIFSFI8iUqHSfI.1&omn=81620949347
_____________________________________________________________________

The records of past talks can be accessed at https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao




Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets tomorrow, Wednesday January 3rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet decided, walk-in speakers will be welcomed. Best, David

Stationary Sets and Algebra, VCU, May 20, 2024

Conference
We will host a workshop at VCU from May 20-22, 2024, on recent applications of set theory to problems in algebra. The website is here: https://stationarysetsandalgebra2024.wordpress.com/ The program and format will depend on the interests and backgrounds of the participants, but the goal is for the workshop to be accessible to graduate students and postdocs who have at least some exposure to set theory, model theory, or logic. The workshop is funded by NSF grant DMS-2154141. Please let Sean Cox (scox9@vcu.edu) know if you are interested in attending. There is some travel funding for student and postdoc participants. Organizers: Sean Cox and Brent Cody
Link to more info

39th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Yinhe Peng from the Academy of Mathematics and Systems Science, CAS. This talk is going to take place this Friday, Dec 29, from 4pm to 5pm(UTC+8, Beijing time). 

Title: The topological basis problem under different assumptions

Abstract: For a class $\mathcal{K}$ of uncountable regular topological spaces, a subclass $\mathcal{B}$ is a basis if every space in $\mathcal{K}$ contains a subspace in $\mathcal{B}$. An important and interesting problem in set-theoretic topology is the topological basis problem: which class of topological spaces has a finite (or even 3-element) basis?

In this talk, I will first briefly recall several known results of the topological basis problem on different classes of spaces. Then, I will introduce recent progress on the topological basis problem under various assumptions. For example, together with Liuzhen Wu, we prove that
(1) under ZF+AD, the class of regular spaces of size $\geq$ continuum has a 3 element basis;
(2) under ZF+AD+V=L($\mathbb{R}$), the class of uncountable regular spaces has a 4 element basis.

I will also introduce definable version of the topological basis problem under ZFC.
_____________________________________________________________________________________________________

Title :The 39th Nankai Logic Colloquium --Yinhe Peng
Time :16:00pm, Dec. 29, 2023(Beijing Time)
Zoom Number : 393 758 7647
Passcode : 055758
Link :https://us06web.zoom.us/j/3937587647?pwd=RdX4CjblPBY3xABriIFSFI8iUqHSfI.1&omn=83015084221
_____________________________________________________________________

The records of past talks can be accessed at https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao




BLAST, North Texas, April 6-9, 2024

Conference
We would like to bring your attention to the upcoming BLAST 2024 conference, which will take place at the University of North Texas in Denton, TX on April 6-9, 2024. There will be an excursion on April 8 to Dallas, TX to witness the total eclipse. BLAST is a conference series focusing on Boolean Algebras, Lattices, Universal Algebra and Model Theory, Set Theory, and Topology. Invited Speakers Monroe Eskew (University of Vienna) Vera Fischer (University of Vienna) Ralph Freese (University of Hawaii) Gabriel Goldberg (UC Berkeley) Jan Grebík (UCLA) Diana Montoya (TU Wien) Justin Moore (Cornell University) Dmitri Pavlov (Texas Tech) Sandra Müller (TU Wien) David Simmons (University of York) Dima Sinapova (Rutgers University) Slawomir Solecki (Cornell University) Šárka Stejskalová (Charles University) Tutorials Andrew Marks (UC Berkeley) Agnes Szendrei (University of Colorado) There is financial support available for students and young researchers which is provided by the NSF to attend the conference and give a contributed talk. Please see the website for details. https://www.math.unt.edu/~ntrang/blast2024/ If you have any questions, feel free to contact us at BLAST2024@unt.edu. Best regards, Lior Fishman, Steve Jackson, John Krueger, Nam Trang
Link to more info

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 20th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet decided, walk-in speakers are welcome. The backup option is Chris Lambie-Hanson giving a spontaneous talk. Let me also remind you that the Christmas meeting of the Institute will take place on Wednesday December 20th at 16:00 in the blue lecture room. All friends of the Institute are invited. Best, David

Set Theory Seminar 19.12.2023 Aleksander Cieślak

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 19.12.2023 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Antichain numbers and other cardinal invariants of ideals "

will be presented by

Aleksander Cieślak


Abstract.

Suppose that J is an ideal on \omega. The J-antichain number is the smallest cardinality of a maximal antichain in the algebra P(\omega) modulo J. We will estimate the J-antichain numbers for various Borel ideals. To do so, we will focus on two features of ideals which are crucial for our construction. First one is a cardinal invariant of an ideal J which lies (strictly) in between add*J and cov*J. The second one is a property which allows diagonalisation of antichains and which is similar (but not equal) to being a P^+ ideal.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

38th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the morning. 

Our speaker this week will be Forte Shinko from the University of California, Berkeley. This talk is going to take place this Friday, Dec 15, from 9am to 10am(UTC+8, Beijing time). 

We are pausing our colloquium for once next week, due to the Annual Meeting of the Chinese Mathematical Society 2023. The Colloquium will be resumed Dec. 29.

Title: Hyperfiniteness of generic actions on Cantor space
Abstract: A countable discrete group is exact if it has a free action on Cantor space which is measure-hyperfinite, that is, for every Borel probability measure on Cantor space, there is a conull set on which the orbit equivalence relation is hyperfinite. For an exact group, it is known that the generic action on Cantor space is measure-hyperfinite, and it is open as to whether the generic action is hyperfinite; an exact group for which the generic action is not hyperfinite would resolve a long-standing open conjecture about whether measure-hyperfiniteness and hyperfiniteness are equivalent. We show that for any countable discrete group with finite asymptotic dimension, its generic action on Cantor space is hyperfinite. This is joint work with Sumun Iyer.
_____________________________________________________________________________________________________
This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title :The 38th Nankai Logic Colloquium --Forte Shinko
Time :9:00am, Dec. 15, 2023(Beijing Time)
Zoom Number : 803 835 0307
Passcode : 266169
Link :https://us06web.zoom.us/j/8038350307?pwd=SisXBBK3gNWNaGdSTQtTbrdCoZn01g.1&omn=84935506346
_____________________________________________________________________

The records of past talks can be accessed from https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao


(KGRC) one talk TOMORROW, December 12, two talks on Thursday, December 14

Kurt Godel Research Center
The KGRC welcomes as guests: David Asperó (host: Monroe Eskew) visits the KGRC from December 11 to December 15. Piotr Kowalski (host: Matthias Aschenbrenner) visits the KGRC from December 13 to December 15. * * * Set Theory Seminar Kurt Gödel Research Center Tuesday, December 12 "Forcing with end-extendible virtual models" David Asperó (University of East Anglia, Norwich, UK) We address the problem of obtaining the saturation of the nonstationary ideal on $\omega_2$ restricted to cofinality $\omega_1$ by forcing with side conditions consisting of virtual models with generators. This is joint work with Boban Velickovic. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, December 14 "Forcing techniques for Cichoń's Maximum: Preservation theory for cardinal characteristics III" Diego Alejandro Mejía (Shizuoka University, JP) Mini-course (30.11.2023-25.01.2024, 6 lectures) - 3rd lecture: We now deal with the more difficult task of forcing the converse inequalities on the left side of Cichon's diagram. We first show how Cohen reals add suitable Tukey connections (or what we also call "strong witnesses"). Next, we need to preserve such Tukey connections along FS iterations. For this purpose, we use a modern device of a preservation technique from Judah and Shelah (1990), and Brendle (1991), illustrating how combinatorial properties of forcing notions influence the preservation of such Tukey connections. However, serious problems related to the bounding number remain, which motivates more recent research that will be presented in the fourth lecture. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, December 14 "Galois actions of finitely generated groups rarely have model companions" Piotr Kowalski (Uniwersytet Wrocławski, PL) This is joint work with Özlem Beyarslan. In our previous work (published as "Model theory of fields with virtually free group actions", Proc. London Math. Soc., (2) 118 (2019), 221-256), we used an erroneous argument in the proof of Theorem 3.6 saying that if $G$ is a finitely generated virtually free group, then the theory of $G$-actions on fields has a model companion. In our recent paper (to appear in Bull. London Math. Soc.), we show a "strong negation" of the statement from Theorem 3.6 above, that is, we show that if $G$ is an infinite finitely generated virtually free group, then the theory of $G$-actions on fields has a model companion if and only if $G$ is free. In this talk, I will present some results and conjectures regarding the companionability of the theory of group actions on fields and (time permitting) discuss some related proofs. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at.

This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

This will be the final edition of This Week in Logic at CUNY for the Fall 2023 semester.  Regular mailings will resume at the end of January.

Wishing you a happy and safe holiday season,
Jonas
 

This Week in Logic at CUNY:

- - - - Monday, Dec 11, 2023 - - - -

Rutgers Logic Seminar
Monday, Dec 11, 3:30pm, Rutgers University, Hill 705
Eyal Kaplan, Berkeley
Preserving the Ultrapower Axiom in forcing extensions



Logic and Metaphysics Workshop
Date: Monday, Dec 11, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Rohit Parikh (CUNY)
Title: The logic of social choice

Abstract: Logic entered social choice theory through Kenneth Arrow who was a student of the logician Alfred Tarski at City College of New York. Arrow’s impossibility result, which was axiomatic in nature, showed that there is no rational procedure to define the popular choice when there are three or more candidates. Arrow’s result led to a rich field. However, subsequent work has concentrated on what happens when voters face a slate of three or more candidates. There is not enough work on a theory of candidate slates themselves. Thus an election with just Donald Trump and Joe Biden is seen as unproblematic since there are only two candidates. The actual quality of the candidates does not matter. We will propose a method which depends on the actual quality of a candidate. Then it becomes a dominant game theoretic strategy for each party to nominate as good a candidate as possible. The goodness of a candidate is defined in terms of a dot product of two vectors: the candidate’s position and the position of a typical voter.





- - - - Tuesday, Dec 12, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Dec 12, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Karel Hrbáček, CUNY
Multi-level nonstandard analysis, the axiom of choice, and recent work of R. Jin

Model-theoretic frameworks for nonstandard methods require the existence of nonprincipal ultrafilters over N, a strong form of the Axiom of Choice (AC). While AC is instrumental in many abstract areas of mathematics, its use in infinitesimal calculus or number theory should not be necessary.

In the paper KH and M. G. Katz, Infinitesimal analysis without the Axiom of Choice, Ann. Pure Applied Logic 172, 6 (2021), https://arxiv.org/abs/2009.04980, we have formulated SPOT, a theory in the language that has, in addition to membership, a unary predicate 'is standard.' The theory extends ZF by three simple axioms, Transfer, Nontriviality and Standard Part, that reflect the insights of Leibniz. It is a subtheory of the nonstandard set theories IST and HST, but unlike them, it is a conservative extension of ZF. Arguments carried out in SPOT thus do not depend on any form of AC. Infinitesimal calculus can be developed in SPOT. A stronger theory SCOT is a conservative extension of ZF + Dependent Choice. It is suitable for handling such features as an infinitesimal approach to the Lebesgue measure.

Renling Jin recently gave a groundbreaking nonstandard proof of Szemeredi's theorem in a model-theoretic framework that has three levels of infinity. I will formulate and motivate SPOTS, a multi-level version of SPOT, carry out Jin's proof of Ramsey's theorem in SPOTS, and discuss how his proof of Szemeredi's theorem can be developed in it.

While it is still open whether SPOTS is conservative over ZF, SCOTS (the multi-level version of SCOT) is a conservative extension of ZF + Dependent Choice.





- - - - Wednesday, Dec 13, 2023 - - - -



- - - - Thursday, Dec 14, 2023 - - - -

* EXAMS WEEK CUNY GRADUATE CENTER *

- - - - Friday, Dec 15, 2023 - - - -



Next Week in Logic at CUNY:

- - - - Monday, Dec 18, 2023 - - - -



- - - - Tuesday, Dec 19, 2023 - - - -



- - - - Wednesday, Dec 20, 2023 - - - -



- - - - Thursday, Dec 21, 2023 - - - -



- - - - Friday, Dec 22, 2023 - - - -




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 13th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Šárka Stejskalová -- Forcing over a free Suslin tree In the talk I will discuss a joint work with John Krueger which leads to a positive solution of a question from 1997 of Jin and Shelah for omega_1-trees: Is there a model where there are no Kurepa trees, but there is a ccc forcing with size at most omega_1 which adds a Kurepa tree? We will start by discussing related concepts of an almost Kurepa Suslin tree and a Suslin tree with more than omega_1-many automorphisms. Then we will sketch a proof for the positive solution of Jin and Shelah's question using a forcing over a free Suslin tree. We will demonstrate the method in more detail by solving another open question by Moore: Is there a model where there are no Kurepa trees, but there is an Aronszajn tree which is not saturated? (An omega_1-tree is said to be saturated if every family of subtrees with pairwise countable intersections has size at most omega_1.) Best, David

37th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Wei He from Nanjing Normal University. This talk is going to take place this Friday, Dec 08, from 9am to 10am(UTC+8, Beijing time). 

Title: Ordered Structure of Topological Groups

Abstract: In this talk, we discuss the ordered structure of the lattices of group topologies on an abstract group. We are in particular concerned with the gaps and distributive conditions of the lattice of group topologies.
We will see that the order structure of the group topologies is closely connected with the algebraic structure and the topological structure of a topological group.

_____________________________________________________________________________________________________

This is going to be an online/offline hybrid event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.
Title :The 37th Nankai Logic Colloquium --Wei He
Time :9:00pm, Dec. 8, 2023(Beijing Time)
Zoom Number : 803 835 0307
Passcode : 266169
_____________________________________________________________________

The records of past talks can be accessed from https://space.bilibili.com/253421893

Best Wishes,

Ming Xiao





(KGRC) CORRECTED: the future of KGRC announcements, plus three talks

Kurt Godel Research Center
The following corrects announcements sent a few minutes ago that stated the wrong time for Julia Wolf. The time is 3:00pm. Apologies for any confusion caused! * * * Dear all, The KGRC needs to reorganize event announcements. This includes the way the list of recipients is maintained. If you would like to receive these announcements in the future, please register your mail address at https://kgrc.univie.ac.at/newsletter/ For next week announcements will be sent to the current list and the new list in parallel. If you do not want to receive event announcements beyond that, no action is required on your part. Thank you! * * * The KGRC welcomes as guests: Andre Nies (host: Matthias Aschenbrenner) visits the KGRC until December 19 and gives a talk, see below. David Asperó (host: Monroe Eskew) visits the KGRC from December 11 to December 15. Piotr Kowalski (host: Matthias Aschenbrenner) visits the KGRC from December 13 to December 15. * * * Model Theory Seminar Kurt Gödel Research Center Wednesday, December 6 "Tame regularity in hypergraphs" Julia Wolf (Cambridge University, UK) Szemerédi's celebrated regularity lemma states, roughly speaking, that the vertex set of any large graph can be partitioned into a bounded number of sets in such a way that all but a small proportion of pairs of sets from this partition induce a 'regular' graph. The example of the half-graph shows that the existence of irregular pairs cannot be ruled out in general. Recognising the half-graph as an instance of the so-called 'order property' from model theory, Malliaris and Shelah proved in 2014 that if one assumes that the large graph contains no half-graphs of a fixed size (as induced bipartite subgraphs), then it is possible to obtain a regularity partition with no irregular pairs. In addition, the number of parts of the partition is polynomial in the regularity parameter, and the density of each regular pair is either close to zero or close to 1. This beautiful result exemplifies a long-standing theme in model theory, namely that stable structures (which are characterised by an absence of large instances of the order property), are extremely well-behaved. In this talk I will present recent joint work with Caroline Terry (OSU), in which we define a higher-arity generalisation of the order property and prove that its absence characterises those large 3-uniform hypergraphs whose regularity decompositions allow for particularly good control of the irregular triads. Time and Place Talk at 3:00pm on-site Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, December 7 "Forcing techniques for Cichoń's Maximum: FS iterations" Diego Alejandro Mejía (Shizuoka University, JP) Mini-course (30.11.2023-25.01.2024, 6 lectures) - 2nd lecture: We review FS (finite support iterations) of forcing notions, basic facts, and how they are typically used to modify cardinal characteristics of the continuum. These tools allow to force “one inequality” of the intended models, but a more complex theory is required to force the “converse inequalities”. The latter will be the main topic of the next session. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, December 7 "The unit conjecture and the unique product property" Andre Nies (University of Auckland, NZ) A torsion free group $G$ satisfies the trivial units property for a field $K$ if the group algebra $K[G]$ only has the trivial units (the ones of the form $kg$, where $k$ is a nonzero field element and $g$ is in $G$). $G$ satisfies the unique product property if for each pair of finite nonempty subsets $A$, $B$ some product in $AB$ can be written uniquely. The unique product property implies the trivial units property for each field. We give an overview over these and related properties, and how to formulate them in first-order logic. We discuss Gardam's 2021 result that $F_2[G]$ (where $F_2$ is the two-element field) fails the unit conjecture for the Hantzsche-Wendt group $G$, and the computational methods used to obtain a counterexample. We discuss work in progress with Heiko Dietrich and Melissa Lee (Monash) that would yield a group $G$ for which the trivial units property for $F_2$ holds but the unique product property fails. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at.

UPDATE - This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Please note the addition of a talk on Dec 11 by Rohit Parikh in the Logic and Metaphysics Workshop.

Best,
Jonas



This Week in Logic at CUNY:

- - - - Monday, Dec 4, 2023 - - - -

Rutgers Logic Seminar
Monday, Dec 4, 3:30pm, Rutgers University, Hill 705
Joel David Hamkins, Notre Dame
The computable model theory of forcing



Logic and Metaphysics Workshop
Date: Monday, Dec 4, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

James Walsh (NYU)
Title: Use and mention in formal languages

Abstract: Quine’s distinction between use and mention is one of the cornerstones of analytic philosophy. The distinction is typically motivated with examples from natural language, but Quine also applied the distinction to the formal languages studied in mathematical logic. I will argue that such expressions are not used in Quine’s sense, so the distinction cannot appropriately be applied to them. Accordingly, the standard practice of placing quotation marks around expressions of formal languages is incorrect. This technical point serves as a springboard for discussing the role that formal languages play in mathematical logic.



- - - - Tuesday, Dec 5, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Dec 5, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Mateusz Łełyk, University of Warsaw

Simplest model properties for Peano Arithmetic: On a question of Montalban and Rossegger

As famously shown by Scott, every countable structure can be characterized, up to isomorphism, by a sentence of infinitary language  which allows for conjunctions and disjunctions over arbitrary countable families of formulae (over finitely many variables). Formulae of this language can be naturally assigned ranks based on the number of alternations of existential connectives (disjunctions and existential quantifiers) with universal ones (conjunctions and universal quantifiers). This gives rise to a natural complexity measure for countable models: the Scott rank of a model  is the least  such that  can be uniquely characterized by a sentence of rank  (and starting from the universal quantifier). The developments of computable model theory witness that the Scott rank is a very robust notion integrating other well established tools from descriptive set theory, model theory and computability.

In 'The Structural Complexity of Models of Arithmetic' Antonio Montalban and Dino Rossegger pioneered the Scott analysis of models of Peano Arithmetic. They characterized the Scott spectrum of completions PA , i.e. the set of ordinals which are Scott ranks of countable models of a given completion  of PA. A particularly intriguing outcome of their analysis is that PA has exactly one model of the least rank, the standard model, and the Scott rank of every other model is infinite. Additionally they studied the connections between Scott ranks and model-theoretical properties of models, such as recursive saturation and atomicity, raising an open question: is there a non-atomic homogeneous model of PA of Scott rank ?

In the talk we answer the above question to the negative, showing that the nonstandard models of PA or rank  are exactly the nonstandard prime models. This witness another peculiar property of PA: not only it has the simplest model, but also its every completion has a unique model of the least Scott rank. This is joint work with Patryk Szlufik.




- - - - Wednesday, Dec 6, 2023 - - - -



- - - - Thursday, Dec 7, 2023 - - - -



- - - - Friday, Dec 8, 2023 - - - -

Model Theory Seminar
Friday, Dec 8, 12:30-2:00pm NY time, Room 5383
David Marker, University of Illinois at Chicago
Rigid real closed fields?

Every archimedean real closed field is rigid, i.e., has no nontrivial automorphisms. What happens in the non-archimedean case? Shelah showed it is consistent that there are uncountable rigid non-archimedean real closed fields. Enayat asked what happens in the countable case. I believe the question is even interesting in the finite transcendence degree case. In this talk I will describe Shelah's proof and discuss some interesting phenomenon that arises even in transcendence degree 2.




Logic Workshop
CUNY Graduate Center
Friday Dec 8, 2:00pm-3:30pm, Room 5417

Michael Benedikt, Oxford University
Nested Data, Views, and Gaifman Coordinization

I will begin with an overview of how implicit definition, and variations of Beth's definability theorem, arise in relational databases, particularly in the context of view rewriting.

We then turn from relational databases to nested relational databases, a model of hierarchical data - 'objects' - where tables can contain tuples whose components are again tables. There is a standard transformation language for this data model, the Nested Relational Calculus (NRC). We show that a variant of Gaifman's coordinatization theorem plays a role in lieu of Beth's theorem, allowing one to generate NRC transformations from several kinds of implicit specifications. We discuss how to generate transformations effectively from specifications, which requires the development of proof-theoretic methods for implicit definability over nested sets.

This is joint work with Ceclia Pradic and Christoph Wernhard.





Next Week in Logic at CUNY:

- - - - Monday, Dec 11, 2023 - - - -

Rutgers Logic Seminar
Monday, Dec 11, 3:30pm, Rutgers University, Hill 705
Eyal Kaplan, Berkeley
Preserving the Ultrapower Axiom in forcing extensions



Logic and Metaphysics Workshop
Date: Monday, Dec 11, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Rohit Parikh (CUNY)
Title: The logic of social choice

Abstract: Logic entered social choice theory through Kenneth Arrow who was a student of the logician Alfred Tarski at City College of New York. Arrow’s impossibility result, which was axiomatic in nature, showed that there is no rational procedure to define the popular choice when there are three or more candidates. Arrow’s result led to a rich field. However, subsequent work has concentrated on what happens when voters face a slate of three or more candidates. There is not enough work on a theory of candidate slates themselves. Thus an election with just Donald Trump and Joe Biden is seen as unproblematic since there are only two candidates. The actual quality of the candidates does not matter. We will propose a method which depends on the actual quality of a candidate. Then it becomes a dominant game theoretic strategy for each party to nominate as good a candidate as possible. The goodness of a candidate is defined in terms of a dot product of two vectors: the candidate’s position and the position of a typical voter.





- - - - Tuesday, Dec 12, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Dec 12, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Karel Hrbáček, CUNY
Multi-level nonstandard analysis, the axiom of choice, and recent work of R. Jin

Model-theoretic frameworks for nonstandard methods require the existence of nonprincipal ultrafilters over N, a strong form of the Axiom of Choice (AC). While AC is instrumental in many abstract areas of mathematics, its use in infinitesimal calculus or number theory should not be necessary.

In the paper KH and M. G. Katz, Infinitesimal analysis without the Axiom of Choice, Ann. Pure Applied Logic 172, 6 (2021), https://arxiv.org/abs/2009.04980, we have formulated SPOT, a theory in the language that has, in addition to membership, a unary predicate 'is standard.' The theory extends ZF by three simple axioms, Transfer, Nontriviality and Standard Part, that reflect the insights of Leibniz. It is a subtheory of the nonstandard set theories IST and HST, but unlike them, it is a conservative extension of ZF. Arguments carried out in SPOT thus do not depend on any form of AC. Infinitesimal calculus can be developed in SPOT. A stronger theory SCOT is a conservative extension of ZF + Dependent Choice. It is suitable for handling such features as an infinitesimal approach to the Lebesgue measure.

Renling Jin recently gave a groundbreaking nonstandard proof of Szemeredi's theorem in a model-theoretic framework that has three levels of infinity. I will formulate and motivate SPOTS, a multi-level version of SPOT, carry out Jin's proof of Ramsey's theorem in SPOTS, and discuss how his proof of Szemeredi's theorem can be developed in it.

While it is still open whether SPOTS is conservative over ZF, SCOTS (the multi-level version of SCOT) is a conservative extension of ZF + Dependent Choice.





- - - - Wednesday, Dec 13, 2023 - - - -



- - - - Thursday, Dec 14, 2023 - - - -

* EXAMS WEEK CUNY GRADUATE CENTER *

- - - - Friday, Dec 15, 2023 - - - -



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

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Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 6th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Wadge classes on omega_1 (2nd attempt) This will be the second attempt at the seminar to introduce a game to compare complexity of constructions of objects of size omega_1. The original motivation was to compare constructions of Aronszajn trees, coherent sequences of functions, gaps in P(omega), and similar objects. I will prove some basic results on the resulting complexity classes. Joint work (in progress) with J. Bergfalk, O. Guzman, M. Hrusak. Best, David

Logic Seminar 5 Dec 2023 15:30 hrs at NUS by Lu Qi

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Tuesday, 5 December 2023, 15:30 hrs Place: NUS, Department of Mathematics, S17#04-04. Speaker: Lu Qi. Title: Convexity of multiplicities of filtrations on local rings Abstract: In this talk, I will discuss some convexity properties of multiplicities of filtrations on a local ring. In particular, the multiplicity function is convex along geodesics. As a major application, this gives a new proof of a theorem due to Xu and Zhuang on the uniqueness of normalized volume minimizers. In order to characterize strict convexity, we introduce the notion of saturation of a filtration, which turns out to be useful in other settings. For example, it allows us to generalizes a theorem by Rees on characterization of when two filtrations have equal multiplicities. It also allows us to introduce a metric on the space of filtrations. Joint Work: This talk is based on joint work with Harold Blum and Yuchen Liu and some ongoing work. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Dec 4, 2023 - - - -

Rutgers Logic Seminar
Monday, Dec 4, 3:30pm, Rutgers University, Hill 705
Joel David Hamkins, Notre Dame
The computable model theory of forcing



Logic and Metaphysics Workshop
Date: Monday, Dec 4, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

James Walsh (NYU)
Title: Use and mention in formal languages

Abstract: Quine’s distinction between use and mention is one of the cornerstones of analytic philosophy. The distinction is typically motivated with examples from natural language, but Quine also applied the distinction to the formal languages studied in mathematical logic. I will argue that such expressions are not used in Quine’s sense, so the distinction cannot appropriately be applied to them. Accordingly, the standard practice of placing quotation marks around expressions of formal languages is incorrect. This technical point serves as a springboard for discussing the role that formal languages play in mathematical logic.



- - - - Tuesday, Dec 5, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Dec 5, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Mateusz Łełyk, University of Warsaw

Simplest model properties for Peano Arithmetic: On a question of Montalban and Rossegger

As famously shown by Scott, every countable structure can be characterized, up to isomorphism, by a sentence of infinitary language  which allows for conjunctions and disjunctions over arbitrary countable families of formulae (over finitely many variables). Formulae of this language can be naturally assigned ranks based on the number of alternations of existential connectives (disjunctions and existential quantifiers) with universal ones (conjunctions and universal quantifiers). This gives rise to a natural complexity measure for countable models: the Scott rank of a model  is the least  such that  can be uniquely characterized by a sentence of rank  (and starting from the universal quantifier). The developments of computable model theory witness that the Scott rank is a very robust notion integrating other well established tools from descriptive set theory, model theory and computability.

In 'The Structural Complexity of Models of Arithmetic' Antonio Montalban and Dino Rossegger pioneered the Scott analysis of models of Peano Arithmetic. They characterized the Scott spectrum of completions PA , i.e. the set of ordinals which are Scott ranks of countable models of a given completion  of PA. A particularly intriguing outcome of their analysis is that PA has exactly one model of the least rank, the standard model, and the Scott rank of every other model is infinite. Additionally they studied the connections between Scott ranks and model-theoretical properties of models, such as recursive saturation and atomicity, raising an open question: is there a non-atomic homogeneous model of PA of Scott rank ?

In the talk we answer the above question to the negative, showing that the nonstandard models of PA or rank  are exactly the nonstandard prime models. This witness another peculiar property of PA: not only it has the simplest model, but also its every completion has a unique model of the least Scott rank. This is joint work with Patryk Szlufik.




- - - - Wednesday, Dec 6, 2023 - - - -



- - - - Thursday, Dec 7, 2023 - - - -



- - - - Friday, Dec 8, 2023 - - - -

Model Theory Seminar
Friday, Dec 8, 12:30-2:00pm NY time, Room 5383
David Marker, University of Illinois at Chicago
Rigid real closed fields?

Every archimedean real closed field is rigid, i.e., has no nontrivial automorphisms. What happens in the non-archimedean case? Shelah showed it is consistent that there are uncountable rigid non-archimedean real closed fields. Enayat asked what happens in the countable case. I believe the question is even interesting in the finite transcendence degree case. In this talk I will describe Shelah's proof and discuss some interesting phenomenon that arises even in transcendence degree 2.




Logic Workshop
CUNY Graduate Center
Friday Dec 8, 2:00pm-3:30pm, Room 5417

Michael Benedikt, Oxford University
Nested Data, Views, and Gaifman Coordinization

I will begin with an overview of how implicit definition, and variations of Beth's definability theorem, arise in relational databases, particularly in the context of view rewriting.

We then turn from relational databases to nested relational databases, a model of hierarchical data - 'objects' - where tables can contain tuples whose components are again tables. There is a standard transformation language for this data model, the Nested Relational Calculus (NRC). We show that a variant of Gaifman's coordinatization theorem plays a role in lieu of Beth's theorem, allowing one to generate NRC transformations from several kinds of implicit specifications. We discuss how to generate transformations effectively from specifications, which requires the development of proof-theoretic methods for implicit definability over nested sets.

This is joint work with Ceclia Pradic and Christoph Wernhard.





Next Week in Logic at CUNY:

- - - - Monday, Dec 11, 2023 - - - -

Rutgers Logic Seminar
Monday, Dec 11, 3:30pm, Rutgers University, Hill 705
Eyal Kaplan, Berkeley
Preserving the Ultrapower Axiom in forcing extensions




- - - - Tuesday, Dec 12, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Dec 12, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Karel Hrbáček, CUNY
Multi-level nonstandard analysis, the axiom of choice, and recent work of R. Jin

Model-theoretic frameworks for nonstandard methods require the existence of nonprincipal ultrafilters over N, a strong form of the Axiom of Choice (AC). While AC is instrumental in many abstract areas of mathematics, its use in infinitesimal calculus or number theory should not be necessary.

In the paper KH and M. G. Katz, Infinitesimal analysis without the Axiom of Choice, Ann. Pure Applied Logic 172, 6 (2021), https://arxiv.org/abs/2009.04980, we have formulated SPOT, a theory in the language that has, in addition to membership, a unary predicate 'is standard.' The theory extends ZF by three simple axioms, Transfer, Nontriviality and Standard Part, that reflect the insights of Leibniz. It is a subtheory of the nonstandard set theories IST and HST, but unlike them, it is a conservative extension of ZF. Arguments carried out in SPOT thus do not depend on any form of AC. Infinitesimal calculus can be developed in SPOT. A stronger theory SCOT is a conservative extension of ZF + Dependent Choice. It is suitable for handling such features as an infinitesimal approach to the Lebesgue measure.

Renling Jin recently gave a groundbreaking nonstandard proof of Szemeredi's theorem in a model-theoretic framework that has three levels of infinity. I will formulate and motivate SPOTS, a multi-level version of SPOT, carry out Jin's proof of Ramsey's theorem in SPOTS, and discuss how his proof of Szemeredi's theorem can be developed in it.

While it is still open whether SPOTS is conservative over ZF, SCOTS (the multi-level version of SCOT) is a conservative extension of ZF + Dependent Choice.





- - - - Wednesday, Dec 13, 2023 - - - -



- - - - Thursday, Dec 14, 2023 - - - -

* EXAMS WEEK CUNY GRADUATE CENTER *

- - - - Friday, Dec 15, 2023 - - - -



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

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Set Theory and Topology Seminar 5.12.2023 Daria Perkowska

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 5.12.2023 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Non-meager filters"

will be presented by

Daria Perkowska


Abstract.

In the talk I will consider filters on \omega in the measurability (and complexity) context.  Also, one can distinguish some natural subclasses of non-meager filters. We say that a filter F is ccc if P(\omega) /F is ccc. Similarly, we say that a filter supports a measure if there is a probability measure \mu on \omega such that F = {A: \mu(A)=1}. I will show that every ultrafilter supports a measure, every measure supporting filter is ccc and every ccc filter is non-meager. So, one can think about these notions as forming some hierarchy of complexity of filters. This hierarchy is strict. Next I will show that for every ultrafilter from the forcing extension (by \mathbb{A}), there is a ground model filter F such that the ultrafilter extends F and there is an injective Boolean homomorphism \varphi: P(\omega) /F \to \mathbb{A}.


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

36th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Victor Hugo Yanez from Nanjing Normal University. This talk is going to take place this Friday, Dec 01, from 4pm to 5pm(UTC+8, Beijing time). 


Title: An introduction to the Markov and Zariski topologies of a group

Abstract: Let $G$ be a group. A subset of $X$ is said to be \emph{elementary algebraic}, if it is the solution set on $G$ of a given equation of the form $g_1 x^{\varepsilon_1} g_2 x^{\varepsilon_2} \cdots g_n x^{\varepsilon_n} = 1$ for some $g_1, \dots, g_n \in G$ and integers $\varepsilon_1, \dots, \varepsilon_n \in \Z$. $X$ is \emph{algebraic} whenever it is an intersection of a finite union of elementary algebraic subsets of $G$. The algebraic subsets of a group $G$ form a basis of closed sets for a unique topology on $G$ known as the Zariski topology of $G$. Meanwhile, the family of all subsets of $G$ which are closed in every Hausdorff group topology of $G$ form a family of closed subsets for another unique topology on $G$ known as the \emph{Markov topology} of $G$. The Markov topology on a group is always finer than its Zariski topology. 

An old 1945 problem of Markov asks whether the Markov and Zariski topologies of a group must always coincide. The goal of this talk is to give a humble introduction to the theory of the Markov and Zariski topologies; from the overall motivation and impact of the classic results of Markov, to more recent advances further enriching the solution of Markov's problem.

_____________________________________________________________________________________________________

This is going to be an online/offline hybrid event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title :The 36th Nankai Logic Colloquium --Victor Hugo Yañez
Time :16:00pm, Dec. 1, 2023(Beijing Time)
Zoom Number : 671 670 2069
Passcode : 773654
Link :https://us05web.zoom.us/j/6716702069?pwd=mhCy9U60VrE8F6YSCOxOlGxIDPFTgx.1&omn=89006488717

_____________________________________________________________________


Best wishes,

Ming Xiao






(KGRC) two seminar talks Thursday, November 30

Kurt Godel Research Center
(The announcements sent a few minutes ago stated the wrong title for Professor Andretta's talk. Below are the corrected announcements. Apologies for any confusion caused!) * * * The KGRC welcomes as guests: David Schrittesser (host: Vera Fischer) visits the KGRC until January 8, 2024. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, November 30 "Forcing techniques for Cichoń's Maximum" Diego Alejandro Mejía (Shizuoka U, JP) Mini-course (30.11.2023-25.01.2024, 6 lectures) - 1st lecture: Cichoń's diagram describes the connections between combinatorial notions related to measure, category, and compactness of sets of irrational numbers. In the second part of the 2010's decade, Goldstern, Kellner and Shelah constructed a forcing model of Cichoń's Maximum (meaning that all non-dependent cardinal characteristics are pairwise different) by using large cardinals. Some years later, we eliminated this large cardinal assumption. In this mini-course, we explore the forcing techniques to construct the Cichoń's Maximum model and much more. Concretely, we discuss the following components: 1. Tukey connections and cardinal characteristics of the continuum 2. Review of FS (finite support) iterations and basic methods to modify cardinal characteristics. 3. Preservation theory for cardinal characteristics. 4. FS iterations with measures and ultrafilters on the natural numbers. 5. Boolean Ultrapowers. 6. Forcing Intersected with submodels. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data by the day before the talk, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, November 30 "Sierpiński's theorem: geometric aspects and definability issues" Alessandro Andretta (U of Turin, IT) There are numerous statements in various areas of mathematics (algebra, analysis, geometry, ...) that are equivalent to the continuum hypothesis (CH). The earliest instance of this phenomenon is Sierpiński's theorem from 1919: CH is equivalent to the existence of two sets covering the plane such that every horizontal line has countable intersection with the first set and every vertical line has countable intersection with the second. Sierpiński's theorem is the blueprint for most other geometric facts that are equivalent to CH. I will survey some of these theorems proved in the last hundred years, and present some new results in this area. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you have not received the Zoom data by the day before the talk, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at.

Cross-Alps Logic Seminar (speaker: Zoltán Vidnyánszky)

Cross-Alps Logic Seminar
On Friday 01.12.2023 at 16.00
Zoltán Vidnyánszky (Eötvös Loránd University)
will give a talk on 
Homomorphisms in the choiceless world

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.

The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2022 'Models, Sets and Classifications'.

All the best,
Vincenzo

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Nov 27, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, Nov 27, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Mircea Dumitru (Bucharest).
Title: Truth with and without satisfaction

Abstract: The talk addresses a quite natural situation in mathematics. When one needs to define a concept and it is not possible to do a direct recursion on the concept itself, what one does is the next best thing which is to perform recursion on a related concept of which the original given concept can be shown to be a special case. Tarski, in his celebrated paper on “The Concept of Truth in Formalized Languages”, cannot give a definition of truth performing direct recursion on the concept of truth itself. Consequently, he settles on a definition in terms of satisfaction. Following Kit Fine and Timothy McCarthy, “Truth without Satisfaction”, I raise the issue of whether such an indirect procedure of giving a definition of truth is necessary or maybe an alternative definition of truth can be given without going through the related concept of satisfaction. My talk will investigate both certain technical and philosophical aspects of the two sets of formal constraints to defining truth with and without satisfaction.





- - - - Tuesday, Nov 28, 2023 - - - -



- - - - Wednesday, Nov 29, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Charlotte Aten, University of Denver.
Date and Time:     Wednesday November 29, 2023, 7:00 - 8:30 PM. ZOOM TALK.
Title:     A categorical semantics for neural networks.

Abstract: In recent work on discrete neural networks, I considered such networks whose activation functions are polymorphisms of finite, discrete relational structures. The general framework I provided was not entirely categorical in nature but did provide a stepping stone to a categorical treatment of neural nets which are definitionally incapable of overfitting. In this talk I will outline how to view neural nets as categories of functors from certain multicategories to a target multicategory. Moreover, I will show that the results of my PhD thesis allow one to systematically define polymorphic learning algorithms for such neural nets in a manner applicable to any reasonable (read: functorial) finite data structure.




- - - - Thursday, Nov 30, 2023 - - - -



- - - - Friday, Dec 1, 2023 - - - -

Model Theory Seminar
Friday, Dec 1, 12:30-2:00pm NY time, Room 5383

Rehana Patel Wesleyan University



Logic Workshop
CUNY Graduate Center
Friday Dec 1, 2:00pm-3:30pm, Room 6417

James Walsh, New York University
Is the consistency operator canonical?

It is a well-known empirical phenomenon that natural axiomatic theories are well-ordered by consistency strength. The restriction to natural theories is necessary; using ad-hoc techniques (such as self-reference and Rosser orderings) one can exhibit non-linearity and ill-foundedness in the consistency strength hierarchy. What explains the contrast between natural theories and axiomatic theories in general?

Our approach to this problem is inspired by work on an analogous problem in recursion theory. The natural Turing degrees  are well-ordered by Turing reducibility, yet the Turing degrees in general are neither linearly ordered nor well-founded, as ad-hoc techniques (such as the priority method) bear out. Martin's Conjecture, which is still unresolved, is a proposed explanation for this phenomenon. In particular, Martin’s Conjecture specifies a way in which the Turing jump is canonical.

After discussing Martin’s Conjecture, we will formulate analogous proof-theoretic hypotheses according to which the consistency operator is canonical. We will then discuss results - both positive and negative - within this framework. Some of these results were obtained jointly with Antonio Montalbán.





Next Week in Logic at CUNY:

- - - - Monday, Dec 4, 2023 - - - -

Rutgers Logic Seminar
Monday, Dec 4, 3:30pm, Rutgers University, Hill 705
Joel David Hamkins, Notre Dame
The computable model theory of forcing



Logic and Metaphysics Workshop
Date: Monday, Dec 4, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

James Walsh (NYU)
Title: Use and mention in formal languages

Abstract: Quine’s distinction between use and mention is one of the cornerstones of analytic philosophy. The distinction is typically motivated with examples from natural language, but Quine also applied the distinction to the formal languages studied in mathematical logic. I will argue that such expressions are not used in Quine’s sense, so the distinction cannot appropriately be applied to them. Accordingly, the standard practice of placing quotation marks around expressions of formal languages is incorrect. This technical point serves as a springboard for discussing the role that formal languages play in mathematical logic.



- - - - Tuesday, Dec 5, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Dec 5, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Mateusz Łełyk, University of Warsaw
Simplest model properties for Peano Arithmetic: On a question of Montalban and Rossegger



- - - - Wednesday, Dec 6, 2023 - - - -



- - - - Thursday, Dec 7, 2023 - - - -



- - - - Friday, Dec 8, 2023 - - - -

Model Theory Seminar
Friday, Dec 8, 12:30-2:00pm NY time, Room 5383
David Marker, University of Illinois at Chicago
Rigid real closed fields?

Every archimedean real closed field is rigid, i.e., has no nontrivial automorphisms. What happens in the non-archimedean case? Shelah showed it is consistent that there are uncountable rigid non-archimedean real closed fields. Enayat asked what happens in the countable case. I believe the question is even interesting in the finite transcendence degree case. In this talk I will describe Shelah's proof and discuss some interesting phenomenon that arises even in transcendence degree 2.




Logic Workshop
CUNY Graduate Center
Friday Dec 8, 2:00pm-3:30pm, Room 6417
Michael Benedikt, Oxford University
Beth definability and nested relations



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Set Theory and Topology Seminar 28.11.2023 Jarosław Swaczyna

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 28.11.2023 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Zoo of ideal Schauder bases"

will be presented by

Jarosław Swaczyna (Łódź University of Technology)


Abstract.

Given a Banach space X, sequence (e_n) of its elements and an ideal I on natural numbers we say that (e_n) is an I-Schauder base if for every x \in X there exists unique sequence of scalars \alpha_n such that series of \alpha_n e_n is I-convergent to X. in such a case one may consider also coordinate functionals e_n^\star. About ten years ago Kadets asked if those functionals are necessarily continuous at least for some nice ideals, eg ideal of sets of density zero. During my talk I will present answer to this question obtained jointly with Tomasz Kania and Noe de Rancourt. I will also present some examples of ideal Schauder bases which are not the classical ones. Second part will be based on ongoing work with Adam Kwela.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday November 29th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Corey Switzer -- Reflecting Ordinals and Forcing Let $n < \omega$ and $\Gamma$ either $\Pi$ or $\Sigma$. An ordinal $\alpha$ is called $\Gamma^1_n$-reflecting if for each $\beta < \alpha$ and each $\Gamma^1_n$-formula $\varphi$ if $L_\alpha \models \varphi(\beta)$ then there is a $\gamma \in (\beta, \alpha)$ so that $L_\gamma \models \varphi(\beta)$ where here $\models$ refers to full second order logic. The least $\Sigma^1_n$-reflecting ordinal is called $\sigma^1_n$ and the least $\Pi^1_n$-ordinal is called $\pi^1_n$. These ordinals provably exist and are countable (for all $n < \omega$). These ordinals arise naturally in proof theory, particularly in calibrating consistency strength of strong arithmetics and weak set theories. Moreover, surprisingly, their relation to one another relies heavily on the background set theory. If $V=L$ then for all $n < \omega$ we have $\sigma^1_{n+3} < \pi^1_{n+3}$ (due to Cutland) while under PD for all $n < \omega$ we have $\sigma^1_n < \pi^1_n$ if and only if $n$ is even (due to Kechris). Surprisingly nothing was known about these ordinals in any model which satisfies neither $V=L$ nor PD. In this talk I will sketch some recent results which aim at rectifying this. In particular we will show that in any generic extension by any number of Cohen or Random reals, a Sacks, Miller or Laver real, or any lightface, weakly homogeneous Borel ccc forcing notion agrees with $L$ about which ordinals are $\Gamma^1_n$-reflecting (for any $n$ and $\Gamma$). Meanwhile, in the generic extension by collapsing $\omega_1$ many interesting things happen, not least amongst them that $\sigma^1_n$ and $\pi^1_n$ are increased - yet still below $\omega_1^L$ for $n > 2$. Along the way we will discuss the plethora of open problems in this area. This is joint work with Juan Aguilera. Best, David

(KGRC) videos, and the Set Theory Seminar talk this Thursday, November 23

Kurt Godel Research Center
The KGRC welcomes as guests: Serhii Bardyla visits the KGRC until November 24. Diego Alejandro Mejía visits the KGRC until January 31, 2024 and gives a second talk, see below: * * * Materials (video recordings, unless stated otherwise) available so far (starting from the beginning of October): October 5, D. Sobota, "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, I": https://ucloud.univie.ac.at/index.php/s/OeIqEX2tRqEa2oP October 12, D. Sobota, "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, II": https://ucloud.univie.ac.at/index.php/s/WmvEh0fgm4OEvQK October 12, R. Kossak, "Undefinability and Absolute Undefinability", video of speaker: https://ucloud.univie.ac.at/index.php/s/V00mfOUWXdgFytV video of slides: https://ucloud.univie.ac.at/index.php/s/hhHrKzzDpuF6G3S October 13, Š. Stejskalová, "Automorphisms of trees": https://ucloud.univie.ac.at/index.php/s/Ih99spR3b3wRomU October 13, L. Schembecker, "Peculiar maximal eventually different families": https://ucloud.univie.ac.at/index.php/s/EVgkWA741l763xU October 13, V. Fischer, "Splitting and bounding at the uncountable": https://ucloud.univie.ac.at/index.php/s/BlPjqyyqE6VzzL6 October 18, A. Bernshteyn, "The Local Lemma in descriptive combinatorics: a survey and recent developments": https://ucloud.univie.ac.at/index.php/s/6kLls3XchP64FSo October 19, D. Sobota, "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, III": https://ucloud.univie.ac.at/index.php/s/SvYDRLOv7c7WPMI October 19, S. Lempp, "Spectra of Computable Models of Strongly Minimal Disintegrated Theories in Rank 1 Languages", video: https://ucloud.univie.ac.at/index.php/s/x5tRgUhjZ4rauDv slides: https://mathematik.univie.ac.at/fileadmin/user_upload/f_mathematik/Events_News/Vortraege_Events/2023-24/KGRC_Logic_Colloquium_2023-10-19_S._Lempp.pdf November 9, D. Sobota, "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, IV": https://ucloud.univie.ac.at/index.php/s/CpkE5Ku9UiEJe2D November 9, D. Rossegger, "Structural complexity notions for foundational theories": https://ucloud.univie.ac.at/index.php/s/27tlQCsbpNWW79Q November 16, D. Sobota, "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, V": https://ucloud.univie.ac.at/index.php/s/NXzwLDNnsJ31Sw3 * * * Set Theory Seminar Kurt Gödel Research Center Thursday, November 23 "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, VI" Damian Sobota (KGRC) Mini-course (05.10.2023-23.11.2023, 6 lectures) - 6th lecture: I will discuss values of the cardinal characteristics of the continuum associated with the Nikodym and Grothendieck properties of Boolean algebras in various models of set theory. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data by the day before the talk, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at.

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
Two quick updates:
Tuesday's MOPA talk is at noon rather than 1pm.
Wednesday's Category Theory Seminar is cancelled.

All best,
Jonas

This Week in Logic at CUNY:

- - - - Monday, Nov 20, 2023 - - - -

Rutgers Logic Seminar
Monday, Nov 20, 3:30pm, Rutgers University, Hill 705
Alexei Miasnikov, Stevens Institute of Technology
First-order classification, non-standard models, and interpretations




Logic and Metaphysics Workshop
Date: Monday, Nov 20, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Marian Călborean (Bucharest).
Title: Vagueness and Frege

Abstract: A constant of Frege’s writing is his rejection of indeterminate predicates in natural language. I follow Frege’s remarks on vagueness from the early “Begriffsschrift” to his mature works, drawing parallels with contemporary theories of vagueness. I critically examine Frege’s arguments for the inconsistency of natural language and argue that the inability to accommodate vagueness and precision in his mature ontology and semantics is mainly due to heuristic rules which he took as essential, not to a deep problem in his fundamental apparatus.



- - - - Tuesday, Nov 21, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Nov 21, 12:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Saeideh Bahrami, Institute for Research in Fundamental Sciences
-small submodels of countable models of arithmetic

There has been a long tradition in the model theory of arithmetic of attributing the combinatorial properties of cardinal numbers in set theory to initial segments. Considering that the most basic use of cardinal numbers is to assign cardinality to sets, we can adapt a similar notion in models of arithmetic in the following way: for a given initial segment  of any model  of a fragment of arithmetic, say I, a subset  of  is called I-small if there exists a coded bijection  in  such that the range of the restriction of  to  is equal to . It turns out that for a given countable nonstandard model  of I, when I is a strong cut, any -small -elementary submodel of  contains , and inherits some good properties of . In this talk, we are going to review such properties through self-embeddings of .





- - - - Wednesday, Nov 22, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Pedro Sota, TBA.
Date and Time:     Wednesday November 22, 2023, 7:00 - 8:30 PM. ZOOM TALK. CANCELLED



- - - - Thursday, Nov 23, 2023 - - - -

*** Graduate Center Closed (Thanksgiving) ***



- - - - Friday, Nov 24, 2023 - - - -

*** Graduate Center Closed (Thanksgiving) ***



Next Week in Logic at CUNY:

- - - - Monday, Nov 27, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, Nov 20, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Mircea Dumitru (Bucharest).
Title: Truth with and without satisfaction

Abstract: The talk addresses a quite natural situation in mathematics. When one needs to define a concept and it is not possible to do a direct recursion on the concept itself, what one does is the next best thing which is to perform recursion on a related concept of which the original given concept can be shown to be a special case. Tarski, in his celebrated paper on “The Concept of Truth in Formalized Languages”, cannot give a definition of truth performing direct recursion on the concept of truth itself. Consequently, he settles on a definition in terms of satisfaction. Following Kit Fine and Timothy McCarthy, “Truth without Satisfaction”, I raise the issue of whether such an indirect procedure of giving a definition of truth is necessary or maybe an alternative definition of truth can be given without going through the related concept of satisfaction. My talk will investigate both certain technical and philosophical aspects of the two sets of formal constraints to defining truth with and without satisfaction.





- - - - Tuesday, Nov 28, 2023 - - - -



- - - - Wednesday, Nov 29, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Charlotte Aten, University of Denver.
Date and Time:     Wednesday November 29, 2023, 7:00 - 8:30 PM. ZOOM TALK.




- - - - Thursday, Nov 30, 2023 - - - -



- - - - Friday, Dec 1, 2023 - - - -

Model Theory Seminar
Friday, Dec 1, 12:30-2:00pm NY time, Room 5383

Rehana Patel Wesleyan University



Logic Workshop
CUNY Graduate Center
Friday Dec 1, 2:00pm-3:30pm, Room 6417
James Walsh New York University
Is the consistency operator canonical?



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

35th Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Kazuyuki Tanaka from the Beijing Institute of Mathematical Sciences and Applications. This talk is going to take place this Friday, Nov 24, from 4pm to 5pm(UTC+8, Beijing time). 


Title: Reverse mathematics and infinite games in differences of ${\mathcal F}_\sigma$ sets

Abstract: Reverse mathematics is a foundational program which aims for answering the following questions: What set existence axioms are needed to prove the theorems of ordinary mathematics? Along this program, the strength of determinacy of infinite games of lower Borel sets has been extensively studied. In this talk, we would like to shed new light on the determinacy hierarchy over the boolean combinations of boldface $\Sigma^0_2$ sets. Among others, we show that such hierarchy collapses above boldface $\Sigma^0_2 \wedge \Pi^0_2$ sets, and the determinacy of boldface $\Delta(\Sigma^0_2 \wedge \Pi^0_2)$ turns out to be equivalent to that of boldface $\Sigma^0_2$. This is a joint work with W.Li and K.Yoshii. 

___________________________________________________________________________________________________________________________________________________


This is going to be an online/offline hybrid event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title :The 35th Nankai Logic Colloquium --Kazuyuki Tanaka

Time :16:00pm, Nov. 24, 2023(Beijing Time)

Zoom Number :847 0296 7631

Passcode :547555

Link :https://zoom.us/j/84702967631?pwd=IApaBiX5Cqv58tVez39772LJdtHpfF.1

_____________________________________________________________________


Best wishes,

Ming Xiao




This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Nov 20, 2023 - - - -

Rutgers Logic Seminar
Monday, Nov 20, 3:30pm, Rutgers University, Hill 705
Alexei Miasnikov, Stevens Institute of Technology
First-order classification, non-standard models, and interpretations




Logic and Metaphysics Workshop
Date: Monday, Nov 20, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Marian Călborean (Bucharest).
Title: Vagueness and Frege

Abstract: A constant of Frege’s writing is his rejection of indeterminate predicates in natural language. I follow Frege’s remarks on vagueness from the early “Begriffsschrift” to his mature works, drawing parallels with contemporary theories of vagueness. I critically examine Frege’s arguments for the inconsistency of natural language and argue that the inability to accommodate vagueness and precision in his mature ontology and semantics is mainly due to heuristic rules which he took as essential, not to a deep problem in his fundamental apparatus.



- - - - Tuesday, Nov 21, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Nov 21, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Saeideh Bahrami, Institute for Research in Fundamental Sciences
-small submodels of countable models of arithmetic

There has been a long tradition in the model theory of arithmetic of attributing the combinatorial properties of cardinal numbers in set theory to initial segments. Considering that the most basic use of cardinal numbers is to assign cardinality to sets, we can adapt a similar notion in models of arithmetic in the following way: for a given initial segment  of any model  of a fragment of arithmetic, say I, a subset  of  is called I-small if there exists a coded bijection  in  such that the range of the restriction of  to  is equal to . It turns out that for a given countable nonstandard model  of I, when I is a strong cut, any -small -elementary submodel of  contains , and inherits some good properties of . In this talk, we are going to review such properties through self-embeddings of .





- - - - Wednesday, Nov 22, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Pedro Sota, TBA.
Date and Time:     Wednesday November 22, 2023, 7:00 - 8:30 PM. ZOOM TALK.



- - - - Thursday, Nov 23, 2023 - - - -

*** Graduate Center Closed (Thanksgiving) ***



- - - - Friday, Nov 24, 2023 - - - -

*** Graduate Center Closed (Thanksgiving) ***



Next Week in Logic at CUNY:

- - - - Monday, Nov 27, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, Nov 20, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Mircea Dumitru (Bucharest).
Title: Truth with and without satisfaction

Abstract: The talk addresses a quite natural situation in mathematics. When one needs to define a concept and it is not possible to do a direct recursion on the concept itself, what one does is the next best thing which is to perform recursion on a related concept of which the original given concept can be shown to be a special case. Tarski, in his celebrated paper on “The Concept of Truth in Formalized Languages”, cannot give a definition of truth performing direct recursion on the concept of truth itself. Consequently, he settles on a definition in terms of satisfaction. Following Kit Fine and Timothy McCarthy, “Truth without Satisfaction”, I raise the issue of whether such an indirect procedure of giving a definition of truth is necessary or maybe an alternative definition of truth can be given without going through the related concept of satisfaction. My talk will investigate both certain technical and philosophical aspects of the two sets of formal constraints to defining truth with and without satisfaction.





- - - - Tuesday, Nov 28, 2023 - - - -



- - - - Wednesday, Nov 29, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Charlotte Aten, University of Denver.
Date and Time:     Wednesday November 29, 2023, 7:00 - 8:30 PM. ZOOM TALK.




- - - - Thursday, Nov 30, 2023 - - - -



- - - - Friday, Dec 1, 2023 - - - -

Model Theory Seminar
Friday, Dec 1, 12:30-2:00pm NY time, Room 5383

Rehana Patel Wesleyan University



Logic Workshop
CUNY Graduate Center
Friday Dec 1, 2:00pm-3:30pm, Room 6417
James Walsh New York University
Is the consistency operator canonical?



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Set Theory and Topology Seminar 21.11.2023 Diego Mejia

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 21.11.2023 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Ultrafilters and finitely additive measures in forcing theory"

will be presented by

Diego Mejia (Shizuoka University)


Abstract.

We show how ultrafilters and finitely additive measures on the power set of the natural numbers can be used in forcing theory to construct models of ZFC where many classical cardinal characteristics have pairwise different values. Very recent remarkable results, like the consistency of Cichon's maximum (the constellation of Cichon's diagram where all non dependent cardinal characteristics are pairwise different), have been proved using such techniques.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday November 22nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Lukas Schembecker -- Peculiar maximal eventually different families In my talk I will discuss a new notion of strong maximality for maximal eventually different families and explore some applications for the corresponding cardinal characteristic $\mathfrak{a}_e$ and its spectrum. ********************************************************************** Moreover, Jindra Zapletal will be giving a three lecture mini-course course "Geometric Set Theory" next week at IM PAN in Warsaw. The lectures will be broadcasted online and people are encouraged to join. The schedule is as follows: 20.11, Mon, 1:30-2:30pm, room 405 21.11, Tue, 12:30-1:30pm, room 405 22.11, Wed, 1:30-2:30pm, room 405 Link to the online streaming is: https://us02web.zoom.us/j/89366420630?pwd=c2hnTDhTelZiV3VCTWd4eG5oTlFlUT09 Abstract of the mini-course is in the attachment. Participants are encouraged to read about the Solovay model either from Jech's "Set Theory" (Millenium Edition) or Schindler's "Set Theory: Exploring Independence and Truth". However, this is not a necessary prerequisite, and the model will be introduced during the first lecture. You can contact Maciej Malicki with questions about the mini-course. Best, David

(KGRC) two seminar talks Thursday, November 16

Kurt Godel Research Center
Set Theory Seminar Kurt Gödel Research Center Thursday, November 16 "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, V" Damian Sobota (KGRC) Mini-course (05.10.2023-23.11.2023, 6 lectures) - 5th lecture: I will continue studying upper and lower bounds for the cardinal characteristics of the continuum associated with the Nikodym and Grothendieck properties of Boolean algebras. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data by the day before the talk, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, November 16 "Iterations with ultrafilter-limits and fam-limits" Diego Alejandro Mejía (Shizuoka U, JP) The method of finite support iterations with fams (finitely additive measures) on the power set of the natural numbers was first developed by Saharon Shelah (2000) to construct a model of ZFC where the cofinality of the covering of measure is countable. This type of iterations, as well as iterations with ultrafilter-limits, has played a fundamental role in recent work about the consistency of Cichon's maximum (with Kellner, Goldstern, and Shelah, also with Tanasie). In this talk, I present recent progress and generalizations of the technique of iterations with ultrafilter-limits and fam-limits, and its effect on some classical cardinal characteristics of the continuum, as developed in joint work with Brendle, Miguel Cardona, and Andrés Uribe-Zapata (as well as in work by Takashi Yamazoe). Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you have not received the Zoom data by the day before the talk, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Nov 13, 2023 - - - -

Rutgers Logic Seminar
Monday, Nov 13, 3:30pm, Rutgers University, Hill 705
Paul Ellis, Rutgers
Finite Tukey Morphisms



Logic and Metaphysics Workshop
Date: Monday, Nov 13, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Alex Skiles (Rutgers).
Title: Against zero-grounding

Abstract: A number of philosophers believe that there is an intelligible distinction between ungrounded truths, which are not grounded in any truths at all, and zero-grounded truths, which are grounded, yet there are no truths that they are grounded in. Rather being a mere academic curiosity, these philosophers have also argued that the notion of zero-grounding can be put to serious metaphysical work. In this paper, we present two arguments against the intelligibility of zero-grounding, and then reject several attempts to make zero-grounding intelligible that have been suggested by its proponents.

Note: This is joint work with Tien-Chun Lo and Gonzalo Rodriguez-Pereyra.



- - - - Tuesday, Nov 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Nov 14, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Mengzhou Sun, National University of Singapore
On the (non)elementarity of cofinal extension

Compared with end extensions, much little is known about cofinal extensions for models of fragments of PA, especially their elementarity. In this talk, I will try to give a complete characterization of the elementarity of cofinal extensions. I will present a systematic way to `compress' the truth of M into the second-order structure of a definable cut, and as a consequence, a correspondence theorem between the first-order theory of M and the second-order theory of the cut. Through this method I will construct several models with special cofinal extension properties. I will also show that every countable model of arithmetic fail to satisfy PA admits a non-elementary cofinal extension. It provides a model-theoretic characterization for PA in terms of cofinal extensions.



- - - - Wednesday, Nov 15, 2023 - - - -



- - - - Thursday, Nov 16, 2023 - - - -



- - - - Friday, Nov 17, 2023 - - - -

Model Theory Seminar
Friday, Nov 17, 12:30-2:00pm NY time, Room 5383

Scott Mutchnik, University of Illinois at Chicago
 Theories

Among the classical properties of unstable theories defined by Shelah, our understanding of the strict order hierarchy, , has remained relatively limited past  at the greatest. Methods originating from stability theory have given insight into the structure of stronger unstable classes, including simple and  theories. In particular, syntactic information about formulas in a first-order theory often corresponds to semantic information about independence in a theory's models, which generalizes phenomena such as linear independence in vector spaces and algebraic independence in algebraically closed fields. We discuss how the fine structure of this independence reveals exponential behavior within the strict order hierarchy, particularly at the levels  for positive integers . Our results suggest a potential theory of independence for  theories, for arbitrarily large values of .




Logic Workshop
CUNY Graduate Center
Friday Nov 17, 2:00pm-3:30pm, Room 6417

Joel David Hamkins, Notre Dame University
The Wordle and Absurdle numbers

We consider the game of infinite Wordle as played on Baire space . The codebreaker can win in finitely many moves against any countable dictionary , but not against the full dictionary of Baire space. The Wordle number is the size of the smallest dictionary admitting such a winning strategy for the codebreaker, the corresponding Wordle ideal is the ideal generated by these dictionaries, which under MA includes all dictionaries of size less than the continuum. The Absurdle number, meanwhile, is the size of the smallest dictionary admitting a winning strategy for the absurdist in the two-player variant, infinite Absurdle. In ZFC there are nondetermined Absurdle games, with neither player having a winning strategy, but if one drops the axiom of choice, then the principle of Absurdle determinacy has large cardinal consistency strength over ZF+DC. This is joint work with Ben De Bondt (Paris).




Next Week in Logic at CUNY:

- - - - Monday, Nov 20, 2023 - - - -

Rutgers Logic Seminar
Monday, Nov 20, 3:30pm, Rutgers University, Hill 705
Alexei Miasnikov, Stevens Institute of Technology




Logic and Metaphysics Workshop
Date: Monday, Nov 20, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Marian Călborean (Bucharest).

Title: Vagueness and Frege

Abstract: A constant of Frege’s writing is his rejection of indeterminate predicates in natural language. I follow Frege’s remarks on vagueness from the early “Begriffsschrift” to his mature works, drawing parallels with contemporary theories of vagueness. I critically examine Frege’s arguments for the inconsistency of natural language and argue that the inability to accommodate vagueness and precision in his mature ontology and semantics is mainly due to heuristic rules which he took as essential, not to a deep problem in his fundamental apparatus.



- - - - Tuesday, Nov 21, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Nov 21, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Saeideh Bahrami, Institute for Research in Fundamental Sciences



- - - - Wednesday, Nov 22, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Pedro Sota, TBA.
Date and Time:     Wednesday November 22, 2023, 7:00 - 8:30 PM. ZOOM TALK.



- - - - Thursday, Nov 23, 2023 - - - -

*** Graduate Center Closed (Thanksgiving) ***



- - - - Friday, Nov 24, 2023 - - - -

*** Graduate Center Closed (Thanksgiving) ***



- - - - Other Logic News - - - -

MEMORIAL FOR DAVISES (forwarded from the FOM list):
Dear FOM,

I've been asked to post an announcement for a special event in memory of Martin and Virginia Davis to be held at the Courant Institute (NYU) on January 26, 2024. Martin Davis was a long-time moderator for FOM. The web page for the event is at
https://cims.nyu.edu/dynamic/conferences/davis-memorial/
The event plans presentations by Allyn Jackson, Eugenio Omodeo and Wilfried Sieg and a session on Memories of Martin and Virginia Davis. 

If you will attend, the organizers request you preregister online so that they can reserve an appropriate room and arrange for building access. The event will also be livestreamed.

People who cannot attend in person may submit a paragraph or two to the organizers to be read aloud at the event.



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Set Theory and Topology Seminar 14.11.2023 Aleksander Cieślak

Wrocław Set Theory Seminar

Szymon Żeberski szymon.zeberski@pwr.edu.pl

sob., 4 lis, 10:22 (8 dni temu)
do UDW: akwiatkowska314@gmail.com, UDW: aleksanderdxpody@gmail.com, UDW: Artsiom, UDW: Bartosz, UDW: Daria, UDW: Dominik, UDW: grzegorz.plebanek@math.uni.wroc.pl, UDW: Igor, UDW: ivanov@math.uni.wroc.pl, UDW: Jacek, UDW: jan.kraszewski@math.uni.wroc.pl, UDW: janusz.pawlikowski@math.uni.wroc.pl, UDW: Jeremiasz, UDW: Joanna, UDW: jswaczyna@wp.pl, UDW: Karina, UDW: Korpalski, UDW: Krzysztof, UDW: Krzysztof, UDW: krzysztof.omiljanowski@math.uni.wroc.pl, UDW: lipecki@impan.gov.pl, UDW: Marcin, UDW: Martinez, UDW: Michał, UDW: Michał, UDW: Michał, UDW: Migacz, UDW: Morawski, UDW: nikiel@uni.opole.pl, UDW: Paweł, UDW: pborod@math.uni.wroc.pl, UDW: rafal.filipow@mat.ug.edu.pl, UDW: Robert, UDW: Robert, UDW: Sebastian, UDW: sebastian.jachimek@math.uni.wroc.pl, UDW: settheorytalks@gmail.com, UDW: mnie, UDW: Szymon, UDW: tomasz.zuchowski@math.uni.wroc.pl, UDW: Widz, UDW: Witold, UDW: Łukasz
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 14.11.2023 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Cofinalities of tree ideals and the shrinking property II"

will be presented by

Aleksander Cieślak


Abstract.

Last time, given a tree type \TT, we investigated a cardinal invariant is(\TT) called "Incompatibility Shrinking Number". It was mentioned that the assumption is(\TT)=\continuum implies that    cof(t^0)>\continuum and that is(\TT) falls in between the additivity and the covering number of the borel part t^0_Bor. We will focus on calculating these two for various Borel ideals.


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

Welcome back to Nankai Logic Colloquium! This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Marcin Sabok from McGill University. This talk is going to take place this Friday, Nov 17, from 9am to 10am(UTC+8, Beijing time). 

Title:
Finding the patterns {x,y,xy,x+y} in colorings of the rationals.

Abstract:
We show that for every coloring of the rationals into finitely many colors, one of the colors contains a set of the form  {x,y,xy,x+yfor some nonzero x and y. Joint work with Matt Bowen

Thank you! I look forward to seeing you next week!

___________________________________________________________________________________________________________________________________________________


This is going to be an online/offline hybrid event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title :The 34th Nankai Logic Colloquium --Marcin Sabok

Time :9:00am, Nov. 17, 2023(Beijing Time)

Zoom Number :872 7448 5609

Passcode :448066

Link :https://zoom.us/j/87274485609?pwd=z90Pn2KFasUa3KbbvQ1d7xSl3eP6rc.1

_____________________________________________________________________


Best wishes,

Ming Xiao






(KGRC) two talks tomorrow, Thursday, November 9

Kurt Godel Research Center
Set Theory Seminar Kurt Gödel Research Center Thursday, November 9 "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, IV" Damian Sobota (KGRC) Mini-course (05.10.2023-23.11.2023, 6 lectures) - 4th lecture: During my 4th talk I'll continue to describe connections between complexity of filters on omega and convergence of finitely supported measures on spaces of the form $N_F=\omega\cup\{F\}$. I'll also show how to relate cardinal characteristics of the continuum to the Grothendieck property and the Nikodym property of Boolean algebras and provide various estimates for them in terms of standard cardinal characteristics from Cichoń's diagram. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, November 9 "Structural complexity notions for foundational theories" Dino Rossegger (TU Wien) I will report on a couple of projects investigating the "structural complexity" of models of first-order theories with foundational character. In a project with Antonio Montalbán, we performed a Scott analysis of models of Peano arithmetic and showed, in layperson's terms, that nonstandard models of arithmetic cannot be simple. More formally, our main result shows that every completion of PA has models of Scott rank alpha for every infinite Scott rank alpha. However, the standard model is the unique model of PA with finite Scott rank. In other work with Uri Andrews and Steffen Lempp, we give a characterization of first-order theories that have a boldface Pi^0_omega complete set of models. As a corollary, we obtain that all sequential theories have a Pi^0_omega complete set of models. At last, I will talk about a new project with Darius Kalociński and Mateusz Łełyk that aims to generalize and improve the results obtained with Montalbán. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Nov 6, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, Nov 6, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Alex Citkin (Metropolitan Telecommunications).
Title: On logics of acceptance and rejection

Abstract: In his book Formalization of Logic, Carnap suggested the following process of refutation: for any set of formulas Γ and any formula α, if Γ ⊢ α and α is rejected, reject Γ. Thus, in contrast to the Łukasiewicz’s approach to refutation, the predicate of rejection is defined on sets of formulas rather than just formulas. In addition to a predicate of rejection, we introduce a predicate of acceptance which is also defined on sets of formulas, and this leads us to constructing two-layered logical systems, the ground layer of which is a conventional deductive system (providing us with means for derivation), and the top layer having predicates of acceptance and rejection. In the case when the set of accepted formulas coincides with the set of theorems of the underlying logic and the set of rejected formulas coincides with the sets of non-theorems, we obtain a conventional deductive system. The predicate of acceptance can be non-adjunctive, and this allows us to use such systems as an alternative approach to defining Jaśkowski style discursive logics.




- - - - Tuesday, Nov 7, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Nov 7, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Stefan Hetzl, Vienna University of Technology

This talk is about the relationship between (weak) arithmetical theories and methods for automated inductive theorem proving. Automating the search for proofs by induction is an important topic in computer science with a history that stretches back decades. A variety of different approaches, algorithms and implementations has been developed.

In this talk I will present a logical approach for understanding the power and limits of methods for automated inductive theorem proving. A central tool are translations of proof systems that are intended for automated proof search into weak arithmetical theories. Another central tool are non-standard models of these weak arithmetical theories.

This approach allows to obtain independence results which are of practical interest in computer science. It also gives rise to a number of new problems and questions about weak arithmetical theories.




- - - - Wednesday, Nov 8, 2023 - - - -

Philog Seminar
The Graduate Center of The City University of New York
November 8, 2023, Wednesday, 10 AM
Zoom meeting, please contact Rohit Parikh for zoom link
Robert Stalnaker (MIT)
Conversational strategy and political discourse



The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Larry Moss, Indiana University, Bloomington .

Date and Time:     Wednesday November 8, 2023, 7:00 - 8:30 PM. ZOOM TALK

Title:     On Kripke, Vietoris, and Hausdorff Polynomial Functors.


Abstract: The Vietoris space of compact subsets of a given Hausdorff space yields an endofunctor V on the category of Hausdorff spaces. Vietoris polynomial endofunctors on that category are built from V, the identity and constant functors by forming products, coproducts and compositions. These functors are known to have terminal coalgebras and we deduce that they also have initial algebras. We present an analogous class of endofunctors on the category of extended metric spaces, using in lieu of V the Hausdorff functor H. We prove that the ensuing Hausdorff polynomial functors have terminal coalgebras and initial algebras. Whereas the canonical constructions of terminal coalgebras for Vietoris polynomial functors takes omega steps, one needs \omega + \omega steps in general for Hausdorff ones. We also give a new proof that the closed set functor on metric spaces has no fixed points.




- - - - Thursday, Nov 9, 2023 - - - -



- - - - Friday, Nov 10, 2023 - - - -

Model Theory Seminar
Friday, Nov 10, 12:30-2:00pm NY time, Room 5383
Alexander Van Abel Wesleyan University

Asymptotics of the Spencer-Shelah Random Graph Sequence

In combinatorics, the Spencer-Shelah random graph sequence is a variation on the independent-edge random graph model. We fix an irrational number , and we probabilistically generate the n-th Spencer-Shelah graph (with parameter ) by taking  vertices, and for every pair of distinct vertices, deciding whether they are connected with a biased coin flip, with success probability . On the other hand, in model theory, an -mac is a class of finite structures, where the cardinalities of definable subsets are particularly well-behaved. In this talk, we will introduce the notion of 'probabalistic -mac' and present an incomplete proof that the Spencer Shelah random graph sequence is an example of one.



Logic Workshop
CUNY Graduate Center
Friday Nov 10, 2:00pm-3:30pm, Room 6417

Victoria Gitman, CUNY
Upward Löwenheim Skolem numbers for abstract logics

Galeotti, Khomskii and Väänänen recently introduced the notion of the upward Löwenheim Skolem (ULS) number for an abstract logic. A cardinal  is the upward Lowenheim Skolem number for a logic  if it is the least cardinal with the property that whenever  is a model of size at least  satisfying a sentence  in , then there are arbitrarily large models  satisfying  and having  as a substructure (not necessarily elementary). If we remove the requirement that  has to be a substructure of , we get the classic notion of a Hanf number. While  proves that every logic has a Hanf number, having a ULS number often turns out to have large cardinal strength. In a joint work with Jonathan Osinski, we study the ULS numbers for several classical logics. We introduce a strengthening of the ULS number, the strong upward Löwenheim Skolem number SULS which strengthens the requirement that  is a substructure to full elementarity in the logic . It is easy to see that both the ULS and the SULS number for a logic  are bounded by the least strong compactness cardinal for , if it exists.



Next Week in Logic at CUNY:

- - - - Monday, Nov 13, 2023 - - - -

Rutgers Logic Seminar
Monday, Nov 13, 3:30pm, Rutgers University, Hill 705
Paul Ellis, Rutgers
Finite Tukey Morphisms


Logic and Metaphysics Workshop
Date: Monday, Nov 13, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Alex Skiles (Rutgers).
Title: Against zero-grounding

Abstract: A number of philosophers believe that there is an intelligible distinction between ungrounded truths, which are not grounded in any truths at all, and zero-grounded truths, which are grounded, yet there are no truths that they are grounded in. Rather being a mere academic curiosity, these philosophers have also argued that the notion of zero-grounding can be put to serious metaphysical work. In this paper, we present two arguments against the intelligibility of zero-grounding, and then reject several attempts to make zero-grounding intelligible that have been suggested by its proponents.

Note: This is joint work with Tien-Chun Lo and Gonzalo Rodriguez-Pereyra.


- - - - Tuesday, Nov 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Nov 14, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Mengzhou Sun, National University of Singapore
On the (non)elementarity of cofinal extension

Compared with end extensions, much little is known about cofinal extensions for models of fragments of PA, especially their elementarity. In this talk, I will try to give a complete characterization of the elementarity of cofinal extensions. I will present a systematic way to `compress' the truth of M into the second-order structure of a definable cut, and as a consequence, a correspondence theorem between the first-order theory of M and the second-order theory of the cut. Through this method I will construct several models with special cofinal extension properties. I will also show that every countable model of arithmetic fail to satisfy PA admits a non-elementary cofinal extension. It provides a model-theoretic characterization for PA in terms of cofinal extensions.



- - - - Wednesday, Nov 15, 2023 - - - -



- - - - Thursday, Nov 16, 2023 - - - -



- - - - Friday, Nov 17, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Nov 17, 2:00pm-3:30pm, Room 6417
Joel David Hamkins Notre Dame University




- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Set Theory and Topology Seminar 7.11.2023 Zdenek Silber

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 7.11.2023 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"A countably tight P(K) space admitting a nonseparable measure"

will be presented by

Zdenek Silber (IM PAN)


Abstract.

In the talk we focus on the relation of countable tightness of the space P(K) of Radon probabilty measures on a compact Hausdorff space K and of existence of measures in P(K) that have uncountable Maharam type. Recall that a topological space X has countable tightness if any element of the closure of a subset A of X lies in the closure of some countable subset of A. A Maharam type of a Radon probability measure mu is the density of the Banach space L1(mu).
It was proven by Fremlin that, under Martin's axiom and negation of continuum hypothesis, for a compact Hausdorff space K the existance of a Radon probability of uncountable type is equivalent to the exitence of a continuous surjection from K onto [0,1]^omega1. Hence, under such assumptions, countable tightness of P(K) implies that there is no Radon probability on K which has uncountable type. Later, Plebanek and Sobota showed that, without any additional set-theoretic assumptions, countable tightness of P(KxK) implies that there is no Radon probability on K which has uncountable type as well. It is thus natural to ask whether the implication "P(K) has countable tightness implies every Radon probability on K has countable type" holds in ZFC.
I will present our joint result with Piotr Koszmider that under diamond principle there is a compact Hausdorff space K such that P(K) has countable tightness but there exists a Radon probability on K of uncountable type.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia


Wednesday seminar

Prague Set Theory Seminar
Dear all, There will be no Wednesday seminar next week November 8th due to the open days of the Institute in Zitna. The seminar on Wednesday November 15th is also cancelled as people will go away for conferences that week. The seminar should meet again on Wednesday November 22nd for a talk of Lukas Schembecker. Best, David

Set Theory and Topology Seminar 3.11.2023 Witold Marciszewski

Wrocław Set Theory Seminar
I am happy to announce that at the (EXTRA) seminar in Set Theory and Topology on Friday 3.11.2023 at 16:15 in room 60x (Mathematical Institute, University of Wrocław) the lecture:
"On \omega-Corson compact spaces and related classes of Eberlein compacta"
will be presented by
Witold Marciszewski (MIM UW)

We meet at the coffee place around 16.00 as usual.
Please write to grzegorz.plebanek@math.uni.wroc.pl if you feel like going to Woo Thai after the seminar.

Abstract:
Recall that a compact space K is Eberlein compact if it can be embedded into some Banach space X equipped with the weak topology; equivalently, for some set \Gamma, K can be embedded into the space c_0( \Gamma), endowed with the pointwise convergence topology.
A compact space K is \omega-Corson compact if, for some set \Gamma, K is homeomorphic to a subset of the \sigma-product of real lines \sigma(R^\Gamma), i.e. the subspace of the product R^\Gamma consisting of functions with finite supports. Clearly, every \omega-Corson compact space is Eberlein compact.
We will present a characterization of \omega-Corson compact spaces, and some other results concerning this class of spaces and related classes of Eberlein compacta.
This is a joint research with Grzegorz Plebanek and Krzysztof Zakrzewski, see
https://arxiv.org/abs/2107.02513

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday November 1st at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Christian Pech -- Homogeneous ultrametric structures (towards two-dimensional Fraısse theory) Abstract attached. Best, David

Cross-Alps Logic Seminar (speaker: Steffen Lempp)

Cross-Alps Logic Seminar
On Friday 03.11.2023 at 16:00

Steffen Lempp (University of Wisconsin)

will give a talk on

The complexity of the class of models of arithmetic

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.

The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] itfor the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2022 'Models, Sets and Classifications'.



Privo di virus.www.avast.com

Cross-Alps Logic Seminar (speaker: Steffen Lempp)

Cross-Alps Logic Seminar
On Friday 03.11.2023 at 16.00
Steffen Lempp (University of Wisconsin)
will give a talk on 
The complexity of the class of models of arithmetic

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2022 'Models, Sets and Classifications'.

All the best,
Vincenzo

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 30, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 30th, 3:30pm, Rutgers University, Hill 705
Filippo Calderoni, Rutgers
Condensation and solvable left-orderable groups


Logic and Metaphysics Workshop
Date: Monday, Oct 30, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Brad Armour-Garb (SUNY Albany).
Title: An approach to property-talk for property nominalists

Abstract: Properties, understood as immanent universals that are repeatable entities which distinct objects can each have at the same time and in different places, are weird, so weird, in fact, that if we could do without them, we probably should do so. An alternative to an approach that sanctions properties might suggest a deflationary view of property-talk according to which the raison d’être of our use of ‘property’ is that it serves a quasi-logical function that is akin to what alethic deflationists claim about truth-talk. Deflationists about property-talk normally subscribe to a form of property nominalism, which rejects the sort of property realism that takes properties to be immanent universals. In this talk, after highlighting some of the weirdness of, or worries for, property realism and explaining why certain forms of property nominalism should not be abided, I highlight the expressive role of property-talk and go on to explain how property-talk performs its roles by introducing what I call “adjectival predicate-variable deflationism” (“APVD”). As I will show, by incorporating APVD into a version of what I have called a “semantic-pretense involving fictionalism” (“SPIF”), we capture the full range of property-talk instances without compromising property nominalism. Time permitting, I will also highlight a virtue of my view, which another form of property nominalism cannot accommodate. If property nominalism is correct, then we should endorse the SPIF account of property-talk that I will develop in this talk.

Note: This is joint work with James A. Woodbridge.




- - - - Tuesday, Oct 31, 2023 - - - -



- - - - Wednesday, Nov 1, 2023 - - - -



- - - - Thursday, Nov 2, 2023 - - - -



- - - - Friday, Nov 3, 2023 - - - -

Model Theory Seminar
Friday, Nov 3, 12:30-2:00pm NY time, Room 5383
Alfred Dolich CUNY
Definable sets in rank two expansions of ordered groups

I will discuss work on burden 2 or dp-rank 2 expansions of theories of densely ordered Abelian groups. Such theories allow for some variety in the topological properties of definable subsets in their models and I'll discuss how diverse the collection of definable subsets in a model may be. For example, is it possible to simultaneously define an infinite discrete set and a dense co-dense subset? Answers to such questions often hinge on whether one is working in the inp-rank or dp-rank case (i.e. whether one assumes NIP or not). I will provide definitions in the talk of all the relevant notions. This is joint work with John Goodrick.



Logic Workshop
CUNY Graduate Center
Friday Nov 3, 2:00pm-3:30pm, Room 6417
Karel Hrbacek, CUNY
Nonstandard methods without the Axiom of Choice

Model-theoretic frameworks for nonstandard methods entail the existence of nonprincipal ultrafilters over N, a strong version of the Axiom of Choice (AC). While AC is instrumental in many abstract areas of mathematics, such as general topology or functional analysis, its use in infinitesimal calculus or number theory should not be necessary.

Mikhail Katz and I have formulated a set theory SPOT in the language that has, in addition to membership, a unary predicate “is standard.” In addition to ZF, the theory has three simple axioms, Transfer, Nontriviality and Standard Part, that reflect the insights of Leibniz. It is a subtheory of the nonstandard set theories IST and HST, but unlike them, it is a conservative extension of ZF. Arguments carried out in SPOT thus do not depend on any form of AC. Infinitesimal calculus can be developed in SPOT as far as the global version of Peano's Theorem (the usual proofs of which use ADC, the Axiom of Dependent Choice). The existence of upper Banach densities can be proved in SPOT.

The conservativity of SPOT over ZF is established by a construction that combines the methods of forcing developed by Ali Enayat for second-order arithmetic and Mitchell Spector for set theory with large cardinals.

A stronger theory SCOT is a conservative extension of ZF+ADC. It is suitable for handling such features as an infinitesimal approach to the Lebesgue measure.

I will also formulate an extension of SPOT to a theory with multiple levels of standardness SPOTS, in which Renling Jin's recent groundbreaking proof of Szemeredi's Theorem can be carried out. While it is an open question whether SPOTS is conservative over ZF, SPOTS + DC (Dependent Choice for relations definable in it) is a conservative extension of ZF + ADC.

Reference: KH and M. G. Katz, Infinitesimal analysis without the Axiom of Choice, Ann. Pure Applied Logic 172, 6 (2021). https://doi.org/10.1016/j.apal.2021.102959https://arxiv.org/abs/2009.04980 






Next Week in Logic at CUNY:

- - - - Monday, Nov 6, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, Nov 6, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Alex Citkin (Metropolitan Telecommunications).
Title: On logics of acceptance and rejection

Abstract: In his book Formalization of Logic, Carnap suggested the following process of refutation: for any set of formulas Γ and any formula α, if Γ ⊢ α and α is rejected, reject Γ. Thus, in contrast to the Łukasiewicz’s approach to refutation, the predicate of rejection is defined on sets of formulas rather than just formulas. In addition to a predicate of rejection, we introduce a predicate of acceptance which is also defined on sets of formulas, and this leads us to constructing two-layered logical systems, the ground layer of which is a conventional deductive system (providing us with means for derivation), and the top layer having predicates of acceptance and rejection. In the case when the set of accepted formulas coincides with the set of theorems of the underlying logic and the set of rejected formulas coincides with the sets of non-theorems, we obtain a conventional deductive system. The predicate of acceptance can be non-adjunctive, and this allows us to use such systems as an alternative approach to defining Jaśkowski style discursive logics.




- - - - Tuesday, Nov 7, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Nov 7, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Stefan Hetzl, Vienna University of Technology



- - - - Wednesday, Nov 8, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Larry Moss, Indiana University, Bloomington .

Date and Time:     Wednesday November 8, 2023, 7:00 - 8:30 PM. ZOOM TALK

Title:     On Kripke, Vietoris, and Hausdorff Polynomial Functors.


Abstract: The Vietoris space of compact subsets of a given Hausdorff space yields an endofunctor V on the category of Hausdorff spaces. Vietoris polynomial endofunctors on that category are built from V, the identity and constant functors by forming products, coproducts and compositions. These functors are known to have terminal coalgebras and we deduce that they also have initial algebras. We present an analogous class of endofunctors on the category of extended metric spaces, using in lieu of V the Hausdorff functor H. We prove that the ensuing Hausdorff polynomial functors have terminal coalgebras and initial algebras. Whereas the canonical constructions of terminal coalgebras for Vietoris polynomial functors takes omega steps, one needs \omega + \omega steps in general for Hausdorff ones. We also give a new proof that the closed set functor on metric spaces has no fixed points.




- - - - Thursday, Nov 9, 2023 - - - -



- - - - Friday, Nov 10, 2023 - - - -

Model Theory Seminar
Friday, Nov 10, 12:30-2:00pm NY time, Room 5383
Alexander Van Abel Wesleyan University


Logic Workshop
CUNY Graduate Center
Friday Nov 10, 2:00pm-3:30pm, Room 6417

Victoria Gitman, CUNY
Upward Löwenheim Skolem numbers for abstract logics

Galeotti, Khomskii and Väänänen recently introduced the notion of the upward Löwenheim Skolem (ULS) number for an abstract logic. A cardinal  is the upward Lowenheim Skolem number for a logic  if it is the least cardinal with the property that whenever  is a model of size at least  satisfying a sentence  in , then there are arbitrarily large models  satisfying  and having  as a substructure (not necessarily elementary). If we remove the requirement that  has to be a substructure of , we get the classic notion of a Hanf number. While  proves that every logic has a Hanf number, having a ULS number often turns out to have large cardinal strength. In a joint work with Jonathan Osinski, we study the ULS numbers for several classical logics. We introduce a strengthening of the ULS number, the strong upward Löwenheim Skolem number SULS which strengthens the requirement that  is a substructure to full elementarity in the logic . It is easy to see that both the ULS and the SULS number for a logic  are bounded by the least strong compactness cardinal for , if it exists.




- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

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Set Theory and Topology Seminar 31.10.2023 Aleksander Cieślak

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 31.10.2023 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Cofinalities of tree ideals and Shrinking Property"

will be presented by

Aleksander Cieślak


Abstract.

If \mathcal{T} is a collection of trees on \Baire, then we define the tree ideal t_0 as a collection of these X\subset \Baire such that each T\in \mathcal{T} has a subtree S\in \mathcal{T} which shares no branches with X. We will be interested in the cofinalities of the tree ideals. In particular, we will focus on the condition, called "Incompatibility Shrinking Property", which implies that cof(t_0)>\continuum. We will consider under what assumptions this property is satisfied for the two types of trees, which are Laver and Miller trees which split positively according to some fixed ideal on \omega.


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday October 25th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is to be be determined. In case anybody is interested in giving a talk, let me know. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 23, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 23rd, 3:30pm, Rutgers University, Hill 705
Forte Shinko, Berkeley
Equivalence relations classifiable by actions of Polish abelian groups



Logic and Metaphysics Workshop
Date: Monday, Oct 23, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Melissa Fusco (Columbia)
Title: Diachronic reasoning with conditionals

Abstract: I will discuss a hybrid decision theory, coinciding sometimes with (traditional) Evidential Decision Theory, but usually with (traditional) Causal Decision Theory, which is inspired by recent work on unified and fully compositional approaches to the probabilities of conditionals. The hybrid theory features a few other loci of interest: the partitionality of acts A ∈ {A} fails, and close attention is paid to how one might (dis)confirm chance hypotheses under the umbrella of the Principal Principle. On this theory, the probabilities of conditionals play a role in underwriting a theory of imaging that follows Skyrms’s Thesis (Skyrms, 1981, 1984). Moreover, the credences it is epistemically rational to assign to these conditionals guides updating on one’s own acts. This implies some departures from Conditionalization, which I defend on epistemological grounds.




- - - - Tuesday, Oct 24, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Oct 24, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Alessandro Berarducci and Marcello Mamino, University of Pisa
Provability logic: models within models in Peano Arithmetic

In 1994 Jech gave a model theoretic proof of Gödel's second incompleteness theorem for Zermelo-Fraenkel set theory in the following form: ZF does not prove that ZF has a model. Kotlarski showed that Jech's proof can be adapted to Peano Arithmetic with the role of models being taken by complete consistent extensions. In this note we take another step in the direction of replacing proof-theoretic by model-theoretic arguments. We show, without passing through the arithmetized completeness theorem, that the existence of a model of PA of complexity  is independent of PA, where a model is identified with the set of formulas with parameters which hold in the model. Our approach is based on a new interpretation of the provability logic of Peano Arithmetic with the modal operator interpreted as truth in every -model.



- - - - Wednesday, Oct 25, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Emilio Minichiello, CUNY Graduate Center.

Date and Time:     Wednesday October 25, 2023, 7:00 - 8:30 PM. IN PERSON TALK (GC 6417)

Title:     A Mathematical Model of Package Management Systems.


Abstract: In this talk, I will review some recent joint work with Gershom Bazerman and Raymond Puzio. The motivation is simple: provide a mathematical model of package management systems, such as the Hackage package respository for Haskell, or Homebrew for Mac users. We introduce Dependency Structures with Choice (DSC) which are sets equipped with a collection of possible dependency sets for every element and satisfying some simple conditions motivated from real life use cases. We define a notion of morphism of DSCs, and prove that the resulting category of DSCs is equivalent to the category of antimatroids, which are mathematical structures found in combinatorics and computer science. We analyze this category, proving that it is finitely complete, has coproducts and an initial object, but does not have all coequalizers. Further, we construct a functor from a category of DSCs equipped with a certain subclass of morphisms to the opposite of the category of finite distributive lattices, making use of a simple finite characterization of the Bruns-Lakser completion.




- - - - Thursday, Oct 26, 2023 - - - -



- - - - Friday, Oct 27, 2023 - - - -

POSTPONED - Model Theory Seminar
Friday, Oct 27, 12:30-2:00pm NY time
David Marker, University of Illinois at Chicago
THIS TALK HAS BEEN POSTPONED TO A LATER DATE (TBD)


Logic Workshop
CUNY Graduate Center
Friday Oct 27, 2:00pm-3:30pm, Room 6417

Arnon Avron, Tel Aviv University
Poincaré-Weyl's predicativity: going beyond 

On the basis of Poincaré and Weyl's view of predicativity as invariance, we develop an extensive framework for predicative, type-free first-order set theory in which  and much bigger ordinals can be defined as von Neumann ordinals. This refutes the accepted view of  as the 'limit of predicativity.' We also explain what is wrong in Feferman-Schütte analysis of predicativity on which this view of  is based.




Next Week in Logic at CUNY:

- - - - Monday, Oct 30, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 30th, 3:30pm, Rutgers University, Hill 705
Paul Ellis, Rutgers

Logic and Metaphysics Workshop
Date: Monday, Oct 30, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Brad Armour-Garb (SUNY Albany).
Title: An approach to property-talk for property nominalists

Abstract: Properties, understood as immanent universals that are repeatable entities which distinct objects can each have at the same time and in different places, are weird, so weird, in fact, that if we could do without them, we probably should do so. An alternative to an approach that sanctions properties might suggest a deflationary view of property-talk according to which the raison d’être of our use of ‘property’ is that it serves a quasi-logical function that is akin to what alethic deflationists claim about truth-talk. Deflationists about property-talk normally subscribe to a form of property nominalism, which rejects the sort of property realism that takes properties to be immanent universals. In this talk, after highlighting some of the weirdness of, or worries for, property realism and explaining why certain forms of property nominalism should not be abided, I highlight the expressive role of property-talk and go on to explain how property-talk performs its roles by introducing what I call “adjectival predicate-variable deflationism” (“APVD”). As I will show, by incorporating APVD into a version of what I have called a “semantic-pretense involving fictionalism” (“SPIF”), we capture the full range of property-talk instances without compromising property nominalism. Time permitting, I will also highlight a virtue of my view, which another form of property nominalism cannot accommodate. If property nominalism is correct, then we should endorse the SPIF account of property-talk that I will develop in this talk.

Note: This is joint work with James A. Woodbridge.



- - - - Tuesday, Oct 31, 2023 - - - -



- - - - Wednesday, Nov 1, 2023 - - - -



- - - - Thursday, Nov 2, 2023 - - - -



- - - - Friday, Nov 3, 2023 - - - -

Model Theory Seminar
Friday, Nov 3, 12:30-2:00pm NY time, Room 5383 (modality TBA)
Alfred Dolich CUNY


Logic Workshop
CUNY Graduate Center
Friday Nov 3, 2:00pm-3:30pm, Room 6417
Karel Hrbacek, CUNY
Nonstandard methods without the Axiom of Choice

Model-theoretic frameworks for nonstandard methods entail the existence of nonprincipal ultrafilters over N, a strong version of the Axiom of Choice (AC). While AC is instrumental in many abstract areas of mathematics, such as general topology or functional analysis, its use in infinitesimal calculus or number theory should not be necessary.

Mikhail Katz and I have formulated a set theory SPOT in the language that has, in addition to membership, a unary predicate “is standard.” In addition to ZF, the theory has three simple axioms, Transfer, Nontriviality and Standard Part, that reflect the insights of Leibniz. It is a subtheory of the nonstandard set theories IST and HST, but unlike them, it is a conservative extension of ZF. Arguments carried out in SPOT thus do not depend on any form of AC. Infinitesimal calculus can be developed in SPOT as far as the global version of Peano's Theorem (the usual proofs of which use ADC, the Axiom of Dependent Choice). The existence of upper Banach densities can be proved in SPOT.

The conservativity of SPOT over ZF is established by a construction that combines the methods of forcing developed by Ali Enayat for second-order arithmetic and Mitchell Spector for set theory with large cardinals.

A stronger theory SCOT is a conservative extension of ZF+ADC. It is suitable for handling such features as an infinitesimal approach to the Lebesgue measure.

I will also formulate an extension of SPOT to a theory with multiple levels of standardness SPOTS, in which Renling Jin's recent groundbreaking proof of Szemeredi's Theorem can be carried out. While it is an open question whether SPOTS is conservative over ZF, SPOTS + DC (Dependent Choice for relations definable in it) is a conservative extension of ZF + ADC.

Reference: KH and M. G. Katz, Infinitesimal analysis without the Axiom of Choice, Ann. Pure Applied Logic 172, 6 (2021). https://doi.org/10.1016/j.apal.2021.102959, https://arxiv.org/abs/2009.04980 




- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT

The 2023 Category Theory Octoberfest will be held on the weekend of October 28th through October 29th. The meeting will be virtual. Following the tradition of past Octoberfests, this is intended to be an informal meeting, covering all areas of category theory and its applications.  Here is the official conference website:

 

https://richardblute.ca/octoberfest-2023/

 

At the moment, you'll find there the schedule with all speakers and titles, as well as the zoom link which will be the same for both days. The abstracts for all the talks will be available shortly.

 



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Logic Seminar Talks at NUS on 24 Oct, 31 Oct and 7 Nov 2023

NUS Logic Seminar
Invitations to the logic seminars in this and the next weeks. As Frank Stephan (who maintains this list) will be overseas, these invitations are sent jointly for 24 October, 31 October and 7 November 2023. Logic Seminar Tuesday 24/10/2023, 17:00 hrs, Room S17#04-06, Department of Mathematics, NUS. Speaker: Ho Meng-Che Title: Word problems of groups as ceers Abstract: Classically, the word problem of a group is the set of words equal to the identity of the group, and we analyze them using Turing reductions. In this talk, we consider the word problem of a group as a computably enumerable equivalence relation (ceer), namely, two words are equivalent if and only if they are equal in the group. We compare ceers using the computable reduction: E is reducible to F if there is a computable function f so that i E j if and only if f(i) F f(j). We will discuss some recent results and see that the landscape of word problems as ceers is very different from the classical theory. For instance, in the classical setting, any Turing degree can be realized as a word problem by first constructing a countable group and then embedding it into a finitely presented group via the Higman embedding theorem. However, we prove that in the ceer setting, there is a group G whose word problem is not universal, but for any nontrivial H, the free product of G and H has a universal word problem. This is a joint work with Uri Andrews and Luca San Mauro. Logic Seminar Tuesday 31/10/2023, 17:00 hrs, Room S17#04-06, Department of Mathematics, NUS. Speaker: Samuel Alfaro Tanuwijaya Title: Generalisations of the Posner Robinson theorem Abstract: The talk will deal with relativised versions of the Posner Robinson theorem and explore how far one can go and how to prove these relatived versions. Logic Seminar Tuesday 07/11/2023, 17:00 hrs, Room S17#04-06, Department of Mathematics, NUS. Speakier: Liu Shixiao Title: Density forcings that collapse the continuum Abstract: Last semester I talked about the upper density Mathias forcing which we prove to be proper. This time we take a look at several similar forcings, each of which collapses the continuum to omega and thus fails to be proper.

(KGRC) talk in the Model Theory Seminar on Wednesday, October 25

Kurt Godel Research Center
Model Theory Seminar Kurt Gödel Research Center Wednesday, October 25 "On Whitney's extension problem in o-minimal structures" Armin Rainer (Universität Wien) In 1934, Whitney raised the question of how one can decide whether a function $f$ defined on a closed subset $X$ of $\mathbb R^n$ is the restriction of a $C^m$ function on $\mathbb R^n$. He gave a characterization in dimension $n=1$. The problem was fully solved by Fefferman in 2006. In this talk, I will discuss a related conjecture: if a semialgebraic function $f : X \to \mathbb R$ has a $C^m$ extension to $\mathbb R^n$, then it has a semialgebraic $C^m$ extension. In particular, I will show that the $C^{1,\omega}$ case of the conjecture is true, even in o-minimal expansions of the real field, where $\omega$ is a definable modulus of continuity. The proof is based on definable Lipschitz selections for affine-set valued maps. This is joint work with Adam Parusinski. Time and Place Talk at 11:30am on-site Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at.

Set Theory and Topology Seminar 24.10.2023 Maciej Korpalski

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 24.10.2023 at 17:15 in room 601 (Mathematical Institute, University of Wrocław) the lecture:
"Straightening almost chains into barely altenating ones"

will be presented by

Maciej Korpalski


Abstract.

Consider an almost chain $\mathcal{A} = \{A_x \subset \omega: x \in X\}$ for some separable linearly ordered set $X$. Such a chain is barely alternating if for all $n \in \omega$ we cannot find elements $x_1 < x_2 < x_3 < x_4$ in $X$ satisfying $n \in A_{x_1}, A_{x_3}$, $n \notin A_{x_2}, A_{x_4}$. We will show that under $MA(\kappa)$, if $|X| \leq \kappa$, then we can straighten our almost chain $\mathcal{A}$ into a barely alternating one by changing at most finitely many elements in each set $A_x$.


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

(KGRC) seminar talks Wednesday, October 18, and Thursday, October 19

Kurt Godel Research Center
The KGRC welcomes as guests: Corey Switzer visits the KGRC until December 31. David Asperó visits the KGRC from December 11 until December 15 and gives a talk, details to be announced at a later time. * * * Model Theory & Set Theory Seminar Kurt Gödel Research Center Wednesday, October 18 "The Local Lemma in descriptive combinatorics: a survey and recent developments" Anton Bernshteyn (Georgia Institute of Technology, Atlanta, US) The Lovász Local Lemma is a classical tool in probabilistic combinatorics with numerous and diverse applications. In this talk, I will survey what is known about the behavior of the Local Lemma in the Borel and measurable context, including some very recent progress, and state several open problems. Parts of this talk are based on joint work with Jing Yu and Felix Weilacher. Time and Place Talk at 10:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, October 19 "Spectra of Computable Models of Strongly Minimal Disintegrated Theories in Rank 1 Languages" Steffen Lempp (University of Wisconsin, Madison, US) In this talk, we study, for a given first-order theory T, which countable models of T can be presented effectively. We consider this question for a particular class of theories, the so-called strongly minimal disintegrated theories, where the countable models can be characterized by their dimension. The spectrum of computable models of T is the subset S of $\omega+1$ such that $\alpha$ is in S if and only if the $\alpha$-th model of T can be effectively presented. We examine the class of strongly minimal disintegrated theories in computable relational languages where each relation symbol defines a set of Morley rank at most 1. We characterize the spectra of computable models of such theories (exactly, with the exception of three sets) under the assumption of bounded arity on the language, and (with the exception of three sets and one specific class of sets) without that assumption. We also determine the exactly seven possible spectra for strongly minimal theories in binary relational languages and show that there are at least nine but no more than eighteen spectra of disintegrated theories in ternary relational languages. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 16, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 16th, 3:30pm, Rutgers University, Hill 705
Justin Moore, Cornell
Large minimal non-σ-scattered linear orders



Logic and Metaphysics Workshop
Date: Monday, Oct 16, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Yale Weiss (CUNY)
Title: Maximal deontic logic

Abstract: The worlds accessible from a given world in Kripke models for deontic logic are often informally glossed as ideal or perfect worlds (at least, relative to the base world). Taking that language seriously, a straightforward but nonstandard semantic implementation using models containing maximally good worlds yields a deontic logic, MD, considerably stronger than that which most logicians would advocate for. In this talk, I examine this logic, its philosophical significance, and its technical properties, as well as those of the logics in its vicinity. The principal technical result is a proof that MD is pretabular (it has no finite characteristic matrix but all of its proper normal extensions do). Along the way, I also characterize all normal extensions of the quirky deontic logic D4H, prove that they are all decidable, and show that D4H has exactly two pretabular normal extensions.



- - - - Tuesday, Oct 17, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Oct 17, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Elliot Glazer, Harvard University
Coin flipping on models of arithmetic to define the standard cut

We will discuss the following claim: 'The standard cut of a model  of PA (or even Q) is uniformly definable with respect to a randomly chosen predicate.' Restricting our consideration to countable models, this claim is true in the usual sense, i.e. there is a formula  such that for any countable model of arithmetic  the set  is Lebesgue measure 1. However, if  is countably saturated, then there is no  such that  is measured by the completed product measure on  We will identify various combinatorial ideals on  that can be used to formalize the original claim with no restriction on the cardinality of  and discuss the relationship between closure properties of these ideals and principles of choice.




- - - - Wednesday, Oct 18, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Michael Shulman, University of San Diego.

Date and Time:     Wednesday October 18, 2023, 7:00 - 8:30 PM.  ZOOM TALK

Title:     The derivator of setoids.


Abstract: The question of "what is a homotopy theory" or "what is a higher category" is already interesting in classical mathematics, but in constructive mathematics (such as the internal logic of a topos) it becomes even more subtle. In particular, existing constructive attempts to formulate a homotopy theory of spaces (infinity-groupoids) have the curious property that their "0-truncated objects" are more general than ordinary sets, being instead some kind of "free exact completion" of the category of sets (a.k.a. "setoids"). It is at present unclear whether this is a necessary feature of a constructive homotopy theory or whether it can be avoided somehow. One way to find some evidence about this question is to use the "derivators" of Heller, Franke, and Grothendieck, as they give us access to higher homotopical structure without depending on a preconcieved notion of what such a thing should be. It turns out that constructively, the free exact completion of the category of sets naturally forms a derivator that has a universal property analogous to the classical category of sets and to the classical homotopy theory of spaces: it is the "free cocompletion of a point" in a certain universe. This suggests that either setoids are an unavoidable aspect of constructive homotopy theory, or more radical modifications to the notion of homotopy theory are needed.



- - - - Thursday, Oct 19, 2023 - - - -



- - - - Friday, Oct 20, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Oct 20, 2:00pm-3:30pm, Room 6417
Rehana Patel, Wesleyan University

The number of ergodic models of an infinitary sentence

Given an -sentence  in a countable language, we call an ergodic -invariant probability measure on the Borel space of countable models of  (having fixed underlying set) an ergodic model of . I will discuss the number of ergodic models of such a sentence , including the case when  is a Scott sentence. This is joint work with N. Ackerman, C. Freer, A. Kruckman and A. Kwiatkowska.





Next Week in Logic at CUNY:

- - - - Monday, Oct 23, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 23rd, 3:30pm, Rutgers University, Hill 705
Forte Shinko, Berkeley


Logic and Metaphysics Workshop
Date: Monday, Oct 23, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Melissa Fusco (Columbia)
Title: Diachronic reasoning with conditionals

Abstract: I will discuss a hybrid decision theory, coinciding sometimes with (traditional) Evidential Decision Theory, but usually with (traditional) Causal Decision Theory, which is inspired by recent work on unified and fully compositional approaches to the probabilities of conditionals. The hybrid theory features a few other loci of interest: the partitionality of acts A ∈ {A} fails, and close attention is paid to how one might (dis)confirm chance hypotheses under the umbrella of the Principal Principle. On this theory, the probabilities of conditionals play a role in underwriting a theory of imaging that follows Skyrms’s Thesis (Skyrms, 1981, 1984). Moreover, the credences it is epistemically rational to assign to these conditionals guides updating on one’s own acts. This implies some departures from Conditionalization, which I defend on epistemological grounds.




- - - - Tuesday, Oct 24, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Oct 24, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Alessandro Berarducci and Marcello Mamino, University of Pisa
Provability logic: models within models in Peano Arithmetic

In 1994 Jech gave a model theoretic proof of Gödel's second incompleteness theorem for Zermelo-Fraenkel set theory in the following form: ZF does not prove that ZF has a model. Kotlarski showed that Jech's proof can be adapted to Peano Arithmetic with the role of models being taken by complete consistent extensions. In this note we take another step in the direction of replacing proof-theoretic by model-theoretic arguments. We show, without passing through the arithmetized completeness theorem, that the existence of a model of PA of complexity  is independent of PA, where a model is identified with the set of formulas with parameters which hold in the model. Our approach is based on a new interpretation of the provability logic of Peano Arithmetic with the modal operator interpreted as truth in every -model.



- - - - Wednesday, Oct 25, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Emilio Minichiello, CUNY Graduate Center.

Date and Time:     Wednesday October 25, 2023, 7:00 - 8:30 PM. IN PERSON TALK (GC 6417)

Title:     A Mathematical Model of Package Management Systems.


Abstract: In this talk, I will review some recent joint work with Gershom Bazerman and Raymond Puzio. The motivation is simple: provide a mathematical model of package management systems, such as the Hackage package respository for Haskell, or Homebrew for Mac users. We introduce Dependency Structures with Choice (DSC) which are sets equipped with a collection of possible dependency sets for every element and satisfying some simple conditions motivated from real life use cases. We define a notion of morphism of DSCs, and prove that the resulting category of DSCs is equivalent to the category of antimatroids, which are mathematical structures found in combinatorics and computer science. We analyze this category, proving that it is finitely complete, has coproducts and an initial object, but does not have all coequalizers. Further, we construct a functor from a category of DSCs equipped with a certain subclass of morphisms to the opposite of the category of finite distributive lattices, making use of a simple finite characterization of the Bruns-Lakser completion.




- - - - Thursday, Oct 26, 2023 - - - -



- - - - Friday, Oct 27, 2023 - - - -

Model Theory Seminar
Friday, Oct 27, 12:30-2:00pm NY time, GC Room 5383
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
David Marker, University of Illinois at Chicago



Logic Workshop
CUNY Graduate Center
Friday Oct 27, 2:00pm-3:30pm, Room 6417

Arnon Avron, Tel Aviv University
Poincaré-Weyl's predicativity: going beyond 

On the basis of Poincaré and Weyl's view of predicativity as invariance, we develop an extensive framework for predicative, type-free first-order set theory in which  and much bigger ordinals can be defined as von Neumann ordinals. This refutes the accepted view of  as the 'limit of predicativity.' We also explain what is wrong in Feferman-Schütte analysis of predicativity on which this view of  is based.



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
NERDS 24.0 (New England Recursion and Definability Seminar)
Date: October 14, 2023
Place: Wellesley College – All talks in Science Center N321
Speakers:
Caleb Camrud (Brown University)
Gihanee Senadheera (Winthrop College)
Alex van Abel (Wesleyan University)
Neil Lutz (Swarthmore College)



CONFERENCE ANNOUNCEMENT
I am glad to announce the first installment of the meeting Groups Logic and Dynamics, on October 21. This will be a one day meeting held in New Brunswick. The format is modelled after the NERDS (https://nerds.math.uconn.edu/), for those of you who are familiar with it.

Please find the webpage containing all relevant information below. Registration is optional but strongly encouraged for planning purpose.

https://sites.math.rutgers.edu/~fc327/GLaDF2023/index.html

- Filippo Calderoni
fc327 (at) math.rutgers.edu


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Set Theory and Topology Seminar 17.10.2023 Viktoriia Brydun

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 17.10.2023 at 17:15 in room 603 (Mathematical Institute, University of Wrocław) the lecture:
"Monad on FMS(•) (Fuzzy Metric Spaces Category)"

will be presented by

Viktoriia Brydun (Ivan Franko Lviv National University)


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Logic Seminar 17 Oct 2023 17:00 hrs by Frank Stephan at NUS Mathematics

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Tuesday, 17 October 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-06 Speaker: Frank Stephan, National University of Singapore Co-Authors: Sanjay Jain, Xiaodong Jia and Ammar Fathin Sabili Title: Addition Machines, Automatic Functions and the Open Problems of Floyd and Knuth Abstract: Floyd and Knuth studied in their 1990 paper addition machines which are machines which can add, subtract and compare integers (<,=,>) in unit time; also the reading or writing of an integer is in unit time. They showed that multiplying and dividing can be done in linear time with six registers and asked in their Open Problem (2) whether this bound can be broken; furthermore, they asked in Open Problem (5) of their paper whether there is a register machine which can output in subquadratic time the powers of two occurring in the binary representation of an integer. The talk answers both questions affirmatively and presents the key ideas and programs to witness this. The slides for the joint paper on addition machines are on https://www.comp.nus.edu.sg/~fstephan/logicseminar.html#weeknine A technical report version of the paper is on https://arxiv.org/abs/2111.08969 The paper appeared in the Journal of Computer and System Sciences volume 136, pages 135-156, 2023 under the title "Addition machines, automatic functions and open problems of Floyd and Knuth". The original paper of Floyd and Knuth appeared in the SIAM Journal on Computing, 19(2), 329-340, 1990 and is available as a technical report on http://infolab.stanford.edu/pub/cstr/reports/cs/tr/89/1268/CS-TR-89-1268.pdf as a scanned version of the report. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

(KGRC) talks Wednesday (TODAY), Thursday, and Friday

Kurt Godel Research Center
The KGRC welcomes as guests: Corey Switzer visits the KGRC until December 31. Roman Kossak visits the KGRC until October 13 and gives a talk (see below). Šárka Stejskalová visits the KGRC until October 15 and gives a talk (see below). Radek Honzík visits the KGRC until October 15 and gives a talk (see below). David Asperó visits the KGRC from December 11 until December 15 and gives a talk, details to be announced at a later time. * * * For a video recording of the first part of Damian Sobota's mini-course, please use https://univienna.zoom.us/rec/share/Q6jN04EmLJVbrEeRBQOkSEHIb3JTcVBCvk5K0974htqthimM5O6UnAHoG6fPgw_N.DPdwRWd4hdgSNpej?startTime=1696498409000 and pass code PG4hg%kX * * * Model Theory Seminar Kurt Gödel Research Center Wednesday, October 11 (TODAY) "Surreal numbers in homotopy type theory" David Raffelsberger (Uni Wien) Since their inception in the 1970s, various constructions of the surreal numbers have been discovered. In the classical setting, they were defined as a special class of so-called Games. They were also constructed as expansions of {−, +} of ordinal length. As another example, J. Conway constructed a field isomorphism between the surreals and the field of Hahn Series with real coefficients on the value group of the surreals. This talk will present a more recent construction, first done in the HoTT book, defining the surreals as a higher-inductive type. The talk is intended for an audience that is not yet familiar with homotopy type theory. Thus, the main part of the talk will be spent introducing the basic concepts of homotopy type theory with the two aims of formalizing first-order logic inside homotopy type theory and defining the surreals as a higher-inductive type. In the last part, we will look at a consequence of the constructive nature of homotopy type theory, namely that the surreals defined this way fail to be (weakly) totally ordered. Time and Place Talk at 11:30am on-site Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, October 12 "Convergence in Banach spaces of measures and cardinal characteristics of the continuum, II" Damian Sobota (KGRC) Mini-course (05.10.2023-23.11.2023, 6 lectures) - 2nd lecture: During the second lecture we will briefly discuss the notion of weak topologies on Banach spaces, after which we state two important theorems concerning convergence of sequences of measures on Boolean algebras: the Grothendieck theorem and Nikodym's Uniform Boundedness Theorem. If time permits, we will prove the latter result. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, October 12 "Undefinability and Absolute Undefinability" Roman Kossak (City University of New York, US) I call a subset of the domain of a countable model absolutely undefinable if the set of its images under automorphisms of the model is uncountable. By the Kueker-Reyes theorem, all sets that are not absolutely undefinable are parametrically definable in $L_{\omega_1 \omega}$. I will survey classical results about first-order undefinability in the standard model of arithmetic, and I will contrast them with some old and some new results about absolute undefinability in nonstandard models of PA. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, October 12 "The tower number and the ultrafilter number on an inaccessible cardinal $\kappa$ with compactness at $\kappa^{++}$" Radek Honzík (Charles University, Prague, CZ) We will use a construction due to Brooke-Taylor, Fischer, Friedman, and Montoya and construct a model where $\kappa$ is inaccessible and we have (among other things) $\kappa^+ = \mathfrak{t}(\kappa) < \mathfrak{u}(\kappa) < 2^\kappa$, and the tree property, and the negation of the weak Kurepa Hypothesis hold at $\kappa^{++}$. This is an application of a general method based on indestructibility of various compactness principles by further forcings. The consistency of $\kappa^+ < \mathfrak{t}(\kappa) \leq \mathfrak{u}(\kappa) < 2^\kappa$ with the same compactness principles remains open because it is not solved by the present technique. Time and Place Talk at 4:45pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, October 12 "Automorphisms of trees" Šárka Stejskalová (Charles University, Prague, CZ) In the talk we will focus on automorphisms of $\omega_1$-trees. We will discuss how to add an automorphism to an $\omega_1$-tree with a well-behaved forcing, and we will identify some restrictions for these forcings (for instance, they cannot be $\sigma$-closed for Suslin trees). In the last part of the talk, we will mention some open questions regarding automorphisms of $\omega_1$-trees. Time and Place Talk at 5:30pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Friday, October 13 "Peculiar maximal eventually different families" Lukas Schembecker (KGRC) In my talk I will discuss a new notion of strong maximality for maximal eventually different families and explore some applications for the corresponding cardinal characteristic $\mathfrak{a}_e$ and its spectrum. Time and Place Talk at 9:45am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Friday, October 13 "Splitting and bounding at the uncountable" Vera Fischer (KGRC) We will discuss some new constellations regards the splitting, bounding and reaping numbers at the uncountable and outline the consistency of $\kappa^+ < \mathfrak{s}(\kappa) < \mathfrak{b}(\kappa) = \mathfrak{d}(\kappa) < \mathfrak{r}(\kappa) = 2^\kappa$, for $\kappa$ supercompact. This is a joint work with Diego Mejia. Time and Place Talk at 10:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you have not received the Zoom data, please contact richard.springer@univie.ac.at. Please direct any other questions about this talk to vera.fischer@univie.ac.at.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 9, 2023 - - - -

CUNY Graduate Center CLOSED TODAY


- - - - Tuesday, Oct 10, 2023 - - - -



- - - - Wednesday, Oct 11, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Thiago Alexandre, University of São Paulo (Brazil).

Date and Time:     Wednesday October 11, 2023, 7:00 - 8:30 PM.

Title:     Internal homotopy theories.


Abstract: The idea of 'Homotopy theories' was introduced by Heller in his seminal paper from 1988. Two years later, Grothendieck discovered the theory of derivators (1990), exposed in his late manuscript Les Dérivateurs, and developed further by several authors. Essentially, there are no significant differences between Heller's homotopy theories and Grothendieck's derivators. They are tautologically the same 2-categorical yoga. However, they come from distinct motivations. For Heller, derivators should be a definitive answer to the question "What is a homotopy theory?", while for Grothendieck, who was strongly inspired by topos cohomology, the first main motivation for derivators was to surpass some technical deficiencies that appeared in the theory of triangulated categories. Indeed, Grothendieck designed the axioms of derivators in light of a certain 2-functorial construction, which associates the corresponding (abelian) derived category to each topos, and more importantly, inverse and direct cohomological images to each geometric morphism. It was from this 2-functorial construction, from where topos cohomology arises, that Grothendieck discovered the axioms of derivators, which are surprisingly the same as Heller's homotopy theories. Nowadays, it is commonly accepted that a homotopy theory is a quasi-category, and they can all be presented by a localizer (M,W), i.e., a couple composed by a category M and a class of arrows in W. This point of view is not so far from Heller, since pre-derivators, quasi-categories, and localizers, are essentially equivalent as an answer to the question "What is a homotopy theory?". In my talk, I will expose these subjects in more detail, and I am also going to explore how to internalize a homotopy theory in an arbitrary (Grothendieck) topos, a problem which strongly relates formal logic and homotopical algebra.



- - - - Thursday, Oct 12, 2023 - - - -



- - - - Friday, Oct 13, 2023 - - - -

Model Theory Seminar
Friday, Oct 13, 12:30-2:00pm NY time, GC Room 5383
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Vincent Guingona Towson University

Vincent Guingona, Towson University
Indivisibility of Classes of Graphs

This talk will discuss my work with Miriam Parnes and four undergraduates which took place last summer at an REU at Towson University. We say that a class of structures in some fixed language is indivisible if, for all structures A in the class and number of colors k, there is a structure B in the class such that, no matter how we color B with k colors, there is a monochromatic copy of A in B. Parnes and I became interested in this property when studying the classification of theories via positive combinatorial configurations. In this talk, following the work with our students, I will examine indivisibility on classes of graphs. In particular, we will look at hereditarily sparse graphs, cographs, perfect graphs, threshold graphs, and a few other classes. This work is joint with Felix Nusbaum, Zain Padamsee, Miriam Parnes, Christian Pippin, and Ava Zinman.





Logic Workshop
CUNY Graduate Center
Friday Oct 13, 2:00pm-3:30pm, Room 6417

Philipp Rothmaler, CUNY
A theorem of Makkai implying the existence of strict Mittag-Leffler modules in a definable subcategory

In 1982 Makkai published a very general theorem about the existence of what he later called principally prime (we call them positive atomic) models of so-called regular theories [FULL CONTINUOUS EMBEDDINGS OF TOPOSES, TAMS 269], which seems to have gone largely unnoticed. (Regular he called those theories that are axiomatized by positive primitive (=pp) implications.) This is a strong existence result in some sort of positive logic in a very general categorical (including non-additive) setting. I first discuss its significance for definable subcategories of modules (=model categories of regular theories of modules), which play an important role in representation theory and module theory in general. Part of this is that there these models are precisely the strict Mittag-Leffler modules contained in and relativized to such definable subcategories. Makkai’s original proof is, in its generality, not easy to follow, and so it is of interest, especially to the algebraic community, to find an easier proof for modules. I present a recent one due to Prest. At the time being it works only for countable rings, in the uncountable case one still has to rely on Makkai’s original proof.



- - - - Saturday, Oct 14, 2023 - - - -

NERDS 24.0
New England Recursion and Definability Seminar
Date: October 14, 2023
Place: Wellesley College – All talks in Science Center N321



Next Week in Logic at CUNY:

- - - - Monday, Oct 16, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 16th, 3:30pm, Rutgers University, Hill 705
Justin Moore, Cornell
Large minimal non-σ-scattered linear orders



Logic and Metaphysics Workshop
Date: Monday, Oct 16, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Yale Weiss (CUNY)
Title: Maximal deontic logic

Abstract: The worlds accessible from a given world in Kripke models for deontic logic are often informally glossed as ideal or perfect worlds (at least, relative to the base world). Taking that language seriously, a straightforward but nonstandard semantic implementation using models containing maximally good worlds yields a deontic logic, MD, considerably stronger than that which most logicians would advocate for. In this talk, I examine this logic, its philosophical significance, and its technical properties, as well as those of the logics in its vicinity. The principal technical result is a proof that MD is pretabular (it has no finite characteristic matrix but all of its proper normal extensions do). Along the way, I also characterize all normal extensions of the quirky deontic logic D4H, prove that they are all decidable, and show that D4H has exactly two pretabular normal extensions.



- - - - Tuesday, Oct 17, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Oct 17, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Elliot Glazer, Harvard University
Coin flipping on models of arithmetic to define the standard cut

We will discuss the following claim: 'The standard cut of a model  of PA (or even Q) is uniformly definable with respect to a randomly chosen predicate.' Restricting our consideration to countable models, this claim is true in the usual sense, i.e. there is a formula  such that for any countable model of arithmetic  the set  is Lebesgue measure 1. However, if  is countably saturated, then there is no  such that  is measured by the completed product measure on  We will identify various combinatorial ideals on  that can be used to formalize the original claim with no restriction on the cardinality of  and discuss the relationship between closure properties of these ideals and principles of choice.




- - - - Wednesday, Oct 18, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html

Speaker:     Michael Shulman, University of San Diego.

Date and Time:     Wednesday October 18, 2023, 7:00 - 8:30 PM.

Title:     The derivator of setoids.




- - - - Thursday, Oct 19, 2023 - - - -



- - - - Friday, Oct 20, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Oct 20, 2:00pm-3:30pm, Room 6417
Rehana Patel, Wesleyan University


- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
NERDS 24.0 (New England Recursion and Definability Seminar)
Date: October 14, 2023
Place: Wellesley College – All talks in Science Center N321
Speakers:
Caleb Camrud (Brown University)
Gihanee Senadheera (Winthrop College)
Alex van Abel (Wesleyan University)
Neil Lutz (Swarthmore College)



CONFERENCE ANNOUNCEMENT
I am glad to announce the first installment of the meeting Groups Logic and Dynamics, on October 21. This will be a one day meeting held in New Brunswick. The format is modelled after the NERDS (https://nerds.math.uconn.edu/), for those of you who are familiar with it.

Please find the webpage containing all relevant information below. Registration is optional but strongly encouraged for planning purpose.

https://sites.math.rutgers.edu/~fc327/GLaDF2023/index.html

- Filippo Calderoni
fc327 (at) math.rutgers.edu


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, There will be no seminar on Wednesday October 11th. Very likely, no seminar on Wednesday October 18th either. John Krueger will be visiting Prague during the week of October 16--20 (however, at there are no plans for him to give any seminar talks, afaik). https://www.math.unt.edu/~jkrueger/ People are encouraged to get in touch with John in case they are interested in interaction. Best, David

Set Theory and Topology Seminar 10.10.2023 Arturo Martinez

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology on Tuesday 10.10.2023 at 17:15 in room 603 (Mathematical Institute, University of Wrocław) the lecture:
"Cardinal invariants related to free sets"

will be presented by

Arturo Martinez


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)

Abstract:

(Joint work with T. Żuchowski) Given a function f without fixed points, an infinite set A is called free for f if f[A] \cap A = \emptyset. In this talk we will discuss some cardinal invariants related to families of free sets and we will discuss their relation between some cardinal invariants related to category and measure.

About 15 minutes before the seminar we invite you for coffee and a chat to social room.


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 2, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 2nd, 3:30pm, Rutgers University, Hill 705
Philip Stetson, Rutgers
Characterizing LEF groups

Philip Stetson (Rutgers) will speak about Characterizing LEF groups.

Abstract: We propose a concrete characterization of locally-embeddable-into-finite (LEF) groups of cardinality larger than the continuum in terms of embeddings into the reduced product of finite symmetric groups. We show that whether this characterization holds is independent of ZFC. Analogous work has been done for the more general class of sofic groups. This is joint work with Simon Thomas.



Logic and Metaphysics Workshop
Date: Monday, Oct 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Brett Topey (Salzburg)
Title: Whence admissibility constraints? From inferentialism to tolerance

Abstract: Prior’s invented connective ‘tonk’ is sometimes taken to reveal a problem for certain inferentialist approaches to metasemantics: according to such approaches, the truth-theoretic features of our expressions are fully determined by the rules of inference we’re disposed to follow, but admitting the ‘tonk’ rules into a language would lead to intuitively absurd results. Inferentialists tend to insist that they can avoid these results: there are constraints on what sets of inference rules can be admitted into a language, the story goes, and the rules governing disruptive expressions like ‘tonk’ are defective and so illegitimate. I argue, though, that from an inferentialist perspective, there’s no genuine sense in which rules like the ‘tonk’ rules are defective; those who endorse the relevant sort of inferentialism turn out to be committed to Carnap’s principle of tolerance. I then sketch an argument to the effect that this, despite appearances, isn’t a problem for inferentialism.



- - - - Tuesday, Oct 3, 2023 - - - -



- - - - Wednesday, Oct 4, 2023 - - - -



- - - - Thursday, Oct 5, 2023 - - - -



- - - - Friday, Oct 6, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Sept 29, 2:00pm-3:30pm, Room 6417

Jenna Zomback, University of Maryland
Ergodic theorems along trees

In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation , one takes averages of a given integrable function over the intervals  in front of the point . We prove a “backward” ergodic theorem for a countable-to-one pmp , where the averages are taken over subtrees of the graph of  that are rooted at  and lie behind  (in the direction of ). Surprisingly, this theorem yields forward ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank, and can be extended to yield ergodic theorems for pmp actions of free semigroups as well. In each case, the averages are taken along subtrees of the standard Cayley graph rooted at the identity. This is joint work with Anush Tserunyan.





Next Week in Logic at CUNY:

- - - - Monday, Oct 9, 2023 - - - -



- - - - Tuesday, Oct 10, 2023 - - - -



- - - - Wednesday, Oct 11, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Thiago Alexandre,
Date and Time:     Wednesday October 11, 2023, 7:00 - 8:30 PM.
Title:     ...derivator.... 


- - - - Thursday, Oct 12, 2023 - - - -



- - - - Friday, Oct 13, 2023 - - - -

Model Theory Seminar
Friday, Oct 13, 12:30-2:00pm NY time, GC Room 5383
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Vincent Guingona Towson University




- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
I am glad to announce the first installment of the meeting Groups Logic and Dynamics, on October 21. This will be a one day meeting held in New Brunswick. The format is modelled after the NERDS (https://nerds.math.uconn.edu/), for those of you who are familiar with it.

Please find the webpage containing all relevant information below. Registration is optional but strongly encouraged for planning purpose.

https://sites.math.rutgers.edu/~fc327/GLaDF2023/index.html

- Filippo Calderoni
fc327 (at) math.rutgers.edu


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday October 4th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Peter Vojtáš -- Infinitary Ramsey theorem RT^3_2 is (strictly?) stronger than Bolzano–Weierstrass theorem? Reverse mathematics offers tools to compare strength of\forall\exists theorems around continuum (considering them in weak PA2). We review some old results on simple cardinal characteristics of continuum (mainly from A. Blass) and reformulate them in Galois–Tukey reductions. Some new observations and problems arose. In our March talk we considered problems with finite instances and various complements – here everything is infinite. Best, David

Update - Logic Workshop cancelled today: This Week in Logic at CUNY

This Week in Logic at CUNY

Hi everyone,

Today's talk by James Walsh in the Logic Workshop is cancelled due to flooding and subway outages.  Everyone be careful out there,

Jonas 



This Week in Logic at CUNY:

- - - - Monday, Sep 25, 2023 - - - -

NO CLASSES AT CUNY TODAY

Rutgers Logic Seminar
Monday, Sept 25th, 3:30pm, Rutgers University, Hill 705
Dima Sinapova, Rutgers
Mutual stationarity and the failure of SCH



- - - - Tuesday, Sep 26, 2023 - - - -



- - - - Wednesday, Sep 27, 2023 - - - -


On Sun, Sep 24, 2023 at 10:39 PM Jonas Reitz <jonasreitz@gmail.com> wrote:
This Week in Logic at CUNY:

- - - - Monday, Sep 25, 2023 - - - -

NO CLASSES AT CUNY TODAY

Rutgers Logic Seminar
Monday, Sept 25th, 3:30pm, Rutgers University, Hill 705
Dima Sinapova, Rutgers
Mutual stationarity and the failure of SCH



- - - - Tuesday, Sep 26, 2023 - - - -



- - - - Wednesday, Sep 27, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Tomáš Gonda, University of Innsbruck.
Date and Time:     Wednesday September 27, 2023, 5:00 - 6:00 PM. ZOOM TALK. NOTE SPECIAL TIME!
Title:     A Framework for Universality in Physics, Computer Science, and Beyond.

Abstract: Turing machines and spin models share a notion of universality according to which some simulate all others. We set up a categorical framework for universality which includes as instances universal Turing machines, universal spin models, NP completeness, top of a preorder, denseness of a subset, and others. By identifying necessary conditions for universality, we show that universal spin models cannot be finite. We also characterize when universality can be distinguished from a trivial one and use it to show that universal Turing machines are non-trivial in this sense. We leverage a Fixed Point Theorem inspired by a result of Lawvere to establish that universality and negation give rise to unreachability (such as uncomputability). As such, this work sets the basis for a unified approach to universality and invites the study of further examples within the framework.





- - - - Thursday, Sep 28, 2023 - - - -



- - - - Friday, Sep 29, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Sept 29, 2:00pm-3:30pm, Room 6417
James Walsh, New York University

Is the consistency operator canonical?

It is a well-known empirical phenomenon that natural axiomatic theories are well-ordered by consistency strength. The restriction to natural theories is necessary; using ad-hoc techniques (such as self-reference and Rosser orderings) one can exhibit non-linearity and ill-foundedness in the consistency strength hierarchy. What explains the contrast between natural theories and axiomatic theories in general?

Our approach to this problem is inspired by work on an analogous problem in recursion theory. The natural Turing degrees  are well-ordered by Turing reducibility, yet the Turing degrees in general are neither linearly ordered nor well-founded, as ad-hoc techniques (such as the priority method) bear out. Martin's Conjecture, which is still unresolved, is a proposed explanation for this phenomenon. In particular, Martin’s Conjecture specifies a way in which the Turing jump is canonical.

After discussing Martin’s Conjecture, we will formulate analogous proof-theoretic hypotheses according to which the consistency operator is canonical. We will then discuss results - both positive and negative - within this framework. Some of these results were obtained jointly with Antonio Montalbán.



Next Week in Logic at CUNY:

- - - - Monday, Oct 2, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 2nd, 3:30pm, Rutgers University, Hill 705
Philip Stetson, Rutgers
Characterizing LEF groups


Logic and Metaphysics Workshop
Date: Monday, Oct 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Brett Topey (Salzburg)
Title: Whence admissibility constraints? From inferentialism to tolerance

Abstract: Prior’s invented connective ‘tonk’ is sometimes taken to reveal a problem for certain inferentialist approaches to metasemantics: according to such approaches, the truth-theoretic features of our expressions are fully determined by the rules of inference we’re disposed to follow, but admitting the ‘tonk’ rules into a language would lead to intuitively absurd results. Inferentialists tend to insist that they can avoid these results: there are constraints on what sets of inference rules can be admitted into a language, the story goes, and the rules governing disruptive expressions like ‘tonk’ are defective and so illegitimate. I argue, though, that from an inferentialist perspective, there’s no genuine sense in which rules like the ‘tonk’ rules are defective; those who endorse the relevant sort of inferentialism turn out to be committed to Carnap’s principle of tolerance. I then sketch an argument to the effect that this, despite appearances, isn’t a problem for inferentialism.



- - - - Tuesday, Oct 3, 2023 - - - -



- - - - Wednesday, Oct 4, 2023 - - - -



- - - - Thursday, Oct 5, 2023 - - - -



- - - - Friday, Oct 6, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Sept 29, 2:00pm-3:30pm, Room 6417

Jenna Zomback, University of Maryland
Ergodic theorems along trees

In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation , one takes averages of a given integrable function over the intervals  in front of the point . We prove a “backward” ergodic theorem for a countable-to-one pmp , where the averages are taken over subtrees of the graph of  that are rooted at  and lie behind  (in the direction of ). Surprisingly, this theorem yields forward ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank, and can be extended to yield ergodic theorems for pmp actions of free semigroups as well. In each case, the averages are taken along subtrees of the standard Cayley graph rooted at the identity. This is joint work with Anush Tserunyan.




- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
I am glad to announce the first installment of the meeting Groups Logic and Dynamics, on October 21. This will be a one day meeting held in New Brunswick. The format is modelled after the NERDS (https://nerds.math.uconn.edu/), for those of you who are familiar with it.

Please find the webpage containing all relevant information below. Registration is optional but strongly encouraged for planning purpose.

https://sites.math.rutgers.edu/~fc327/GLaDF2023/index.html

- Filippo Calderoni
fc327 (at) math.rutgers.edu


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Sep 25, 2023 - - - -

NO CLASSES AT CUNY TODAY

Rutgers Logic Seminar
Monday, Sept 25th, 3:30pm, Rutgers University, Hill 705
Dima Sinapova, Rutgers
Mutual stationarity and the failure of SCH



- - - - Tuesday, Sep 26, 2023 - - - -



- - - - Wednesday, Sep 27, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Tomáš Gonda, University of Innsbruck.
Date and Time:     Wednesday September 27, 2023, 5:00 - 6:00 PM. ZOOM TALK. NOTE SPECIAL TIME!
Title:     A Framework for Universality in Physics, Computer Science, and Beyond.

Abstract: Turing machines and spin models share a notion of universality according to which some simulate all others. We set up a categorical framework for universality which includes as instances universal Turing machines, universal spin models, NP completeness, top of a preorder, denseness of a subset, and others. By identifying necessary conditions for universality, we show that universal spin models cannot be finite. We also characterize when universality can be distinguished from a trivial one and use it to show that universal Turing machines are non-trivial in this sense. We leverage a Fixed Point Theorem inspired by a result of Lawvere to establish that universality and negation give rise to unreachability (such as uncomputability). As such, this work sets the basis for a unified approach to universality and invites the study of further examples within the framework.





- - - - Thursday, Sep 28, 2023 - - - -



- - - - Friday, Sep 29, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Sept 29, 2:00pm-3:30pm, Room 6417
James Walsh, New York University

Is the consistency operator canonical?

It is a well-known empirical phenomenon that natural axiomatic theories are well-ordered by consistency strength. The restriction to natural theories is necessary; using ad-hoc techniques (such as self-reference and Rosser orderings) one can exhibit non-linearity and ill-foundedness in the consistency strength hierarchy. What explains the contrast between natural theories and axiomatic theories in general?

Our approach to this problem is inspired by work on an analogous problem in recursion theory. The natural Turing degrees  are well-ordered by Turing reducibility, yet the Turing degrees in general are neither linearly ordered nor well-founded, as ad-hoc techniques (such as the priority method) bear out. Martin's Conjecture, which is still unresolved, is a proposed explanation for this phenomenon. In particular, Martin’s Conjecture specifies a way in which the Turing jump is canonical.

After discussing Martin’s Conjecture, we will formulate analogous proof-theoretic hypotheses according to which the consistency operator is canonical. We will then discuss results - both positive and negative - within this framework. Some of these results were obtained jointly with Antonio Montalbán.



Next Week in Logic at CUNY:

- - - - Monday, Oct 2, 2023 - - - -

Rutgers Logic Seminar
Monday, Oct 2nd, 3:30pm, Rutgers University, Hill 705
Philip Stetson, Rutgers
Characterizing LEF groups


Logic and Metaphysics Workshop
Date: Monday, Oct 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Brett Topey (Salzburg)
Title: Whence admissibility constraints? From inferentialism to tolerance

Abstract: Prior’s invented connective ‘tonk’ is sometimes taken to reveal a problem for certain inferentialist approaches to metasemantics: according to such approaches, the truth-theoretic features of our expressions are fully determined by the rules of inference we’re disposed to follow, but admitting the ‘tonk’ rules into a language would lead to intuitively absurd results. Inferentialists tend to insist that they can avoid these results: there are constraints on what sets of inference rules can be admitted into a language, the story goes, and the rules governing disruptive expressions like ‘tonk’ are defective and so illegitimate. I argue, though, that from an inferentialist perspective, there’s no genuine sense in which rules like the ‘tonk’ rules are defective; those who endorse the relevant sort of inferentialism turn out to be committed to Carnap’s principle of tolerance. I then sketch an argument to the effect that this, despite appearances, isn’t a problem for inferentialism.



- - - - Tuesday, Oct 3, 2023 - - - -



- - - - Wednesday, Oct 4, 2023 - - - -



- - - - Thursday, Oct 5, 2023 - - - -



- - - - Friday, Oct 6, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Sept 29, 2:00pm-3:30pm, Room 6417

Jenna Zomback, University of Maryland
Ergodic theorems along trees

In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation , one takes averages of a given integrable function over the intervals  in front of the point . We prove a “backward” ergodic theorem for a countable-to-one pmp , where the averages are taken over subtrees of the graph of  that are rooted at  and lie behind  (in the direction of ). Surprisingly, this theorem yields forward ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank, and can be extended to yield ergodic theorems for pmp actions of free semigroups as well. In each case, the averages are taken along subtrees of the standard Cayley graph rooted at the identity. This is joint work with Anush Tserunyan.




- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
I am glad to announce the first installment of the meeting Groups Logic and Dynamics, on October 21. This will be a one day meeting held in New Brunswick. The format is modelled after the NERDS (https://nerds.math.uconn.edu/), for those of you who are familiar with it.

Please find the webpage containing all relevant information below. Registration is optional but strongly encouraged for planning purpose.

https://sites.math.rutgers.edu/~fc327/GLaDF2023/index.html

- Filippo Calderoni
fc327 (at) math.rutgers.edu


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday September 27th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Ziemowit Kostana -- Separating big and small sticks "Stick" is a principle stating there exists a family F, consisting of ω_1 many countable subsets of ω_1, such that each uncountable subset of ω_1 contains a set from F. "Stick" trivially follows from CH, and is consistent with arbitrarily large continuum. A natural question connected with it, is whether we can assume (i.e. without obtaining a strictly stronger axiom) that the sets from F have a given large ordertype, say ω^ω. A claimed negative answer was given by William Chen in the paper Variations of the stick principle, European Journal of Mathematics, 3(3), 650-658. Although the proof is based on a correct (and to me pretty awesome) idea, it contains a substantial gap. I will elaborate on how, and to what extent, the proof can be fixed. Best, David

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday September 20th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Chodounsky -- Wadge classes on omega_1 I will introduce a game to compare complexity of constructions of objects of size omega_1. The original motivation was to compare constructions of Aronszajn trees, coherent sequences of functions, gaps in P(omega), and similar objects. I will prove some basic results on the resulting complexity classes. Joint work (in progress) with J. Bergfalk, O. Guzman, M. Hrusak. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Sep 18, 2023 - - - -

Rutgers Logic Seminar
Monday, Sept 18th, 3:30pm, Rutgers University, Hill 705
Alex Kruckman (Wesleyan)
The complexity of ages admitting a universal limit structure.

Abstract: An age is a hereditary class of finitely generated structures with the joint embedding property which is countable up to isomorphism. If K is an age, a K-limit is a countable structure M such that every finitely generated substructure of M is in K. A K-limit U is universal if every K-limit embeds in U. It is well-known that K has the amalgamation property (AP) if and only if K admits a homogeneous limit (the Fraïssé limit), which is universal. But not every age with a universal limit has AP. We show that, while the existence of a universal limit can be characterized by the well-definedness of a certain ordinal-valued rank on structures in K, it is not equivalent to any finitary diagrammatic property like AP. More precisely, we show that for ages in a fixed sufficiently rich language L, the property of admitting a universal limit is complete coanalytic. This is joint work with Aristotelis Panagiotopoulos.




Logic and Metaphysics Workshop
Date: Monday, Sept 18, 4.15-6.15pm (NY time)
Room: Philosophy Program Thesis Room (in 7113)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Will Nava (NYU)
Title: Non-classicality all the way up

Abstract: Nearly all non-classical logics that have been studied admit of classical reasoning about them. For example, in the logic K3, A or not-A is not a valid schema. However, ‘A or not-A’ is K3-valid or not K3-valid—this is, in some sense, a valid claim. In this talk, I introduce a simple framework for thinking about the logic of a given logic. This allows for a measure of the non-classicality of a logic—one on which almost all familiar non-classical logics are of the lowest grade of non-classicality. I’ll then discuss some strategies for generating and theorizing logics of higher grades of non-classicality, as well as some motivation for taking these logics seriously.




- - - - Tuesday, Sep 19, 2023 - - - -



- - - - Wednesday, Sep 20, 2023 - - - -



- - - - Thursday, Sep 21, 2023 - - - -

Infinite Games Workshop
Zoom Talk, details at https://jdh.hamkins.org/infinite-games-workshop/
Thursday 21 September, 11 am
Speaker: Davide Leonessi, The Graduate Center of the City University of New York
Title: Infinite draughts: a solved open game

Abstract: In this talk I will introduce open infinite games, and then define a natural generalization of draughts (checkers) to the infinite planar board. Infinite draughts is an open game, giving rise to the game value phenomenon and expressing it fully—the omega one of draughts is true $\omega_1$ and every possible defensive strategy of the losing player can be implemented.



- - - - Friday, Sep 22, 2023 - - - -

Model Theory Seminar
CUNY Graduate Center, Room 5383
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Friday, Sept 22, 12:30-2:00pm
Michael Benedikt, University of Oxford
TBA




Logic Workshop
CUNY Graduate Center
Friday Sept 22, 2:00pm-3:30pm, Room 6417

David Marker, University of Illinois at Chicago
On equations of Poizat type

We look at differential equations of the form  where  is a rational function over the field of constants. We characterize when such equations are strongly minimal and study algebraic relations between solutions to two such equations.




Next Week in Logic at CUNY:

- - - - Monday, Sep 25, 2023 - - - -



- - - - Tuesday, Sep 26, 2023 - - - -



- - - - Wednesday, Sep 27, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Tomáš Gonda, University of Innsbruck.
Date and Time:     Wednesday September 27, 2023, 5:00 - 6:00 PM. ZOOM TALK. NOTE SPECIAL TIME!
Title:     A Framework for Universality in Physics, Computer Science, and Beyond.

Abstract: Turing machines and spin models share a notion of universality according to which some simulate all others. We set up a categorical framework for universality which includes as instances universal Turing machines, universal spin models, NP completeness, top of a preorder, denseness of a subset, and others. By identifying necessary conditions for universality, we show that universal spin models cannot be finite. We also characterize when universality can be distinguished from a trivial one and use it to show that universal Turing machines are non-trivial in this sense. We leverage a Fixed Point Theorem inspired by a result of Lawvere to establish that universality and negation give rise to unreachability (such as uncomputability). As such, this work sets the basis for a unified approach to universality and invites the study of further examples within the framework.





- - - - Thursday, Sep 28, 2023 - - - -



- - - - Friday, Sep 29, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Sept 29, 2:00pm-3:30pm, Room 6417
James Walsh, New York University


- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
I am glad to announce the first installment of the meeting Groups Logic and Dynamics, on October 21. This will be a one day meeting held in New Brunswick. The format is modelled after the NERDS (https://nerds.math.uconn.edu/), for those of you who are familiar with it.

Please find the webpage containing all relevant information below. Registration is optional but strongly encouraged for planning purpose.

https://sites.math.rutgers.edu/~fc327/GLaDF2023/index.html

- Filippo Calderoni
fc327 (at) math.rutgers.edu


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Logic Seminar 19 Sept 2023 17:00 hrs at NUS by Neoh Tzeh Yuan

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Tuesday, 19 September 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-06 Speaker: Neoh Tzeh Yuan Title: The complexity of 3-Occur-SAT. Abstract: The Boolean satisfiabilty problem (SAT) is a problem with great theoretical and practical interest. While heuristic algorithms tend to work well in practice, the widely believed strong exponential time hypothesis (SETH) conjectures that there is no deterministic algorithm for SAT in time O(c^n) for some constant c < 2. On the other hand, better bounds of O(c^n) with c < 2 have been found for various restricted (but still NP-complete) instances of SAT. One such problem is 3-Occur-SAT, where every variable in the formula occurs at most 3 times. Wahlstroem presented in 2005 an algorithm which solves the problem in time O(1.1279^n) and Peng and Xiao improved it (this year's IJCAI) to O(1.1238^n). I will present an algorithm that gives a further improvement to O(1.1199^n). I'll discuss the common bottleneck cases faced by previous efforts and introduce new reduction and branching rules that can circumvent these cases. The work I present is done in an internship at NUS / SOC supervised by Sanjay Jain and Frank Stephan from July to September 2023. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Sep 11, 2023 - - - -

Rutgers Logic Seminar
Monday, Sept 11th, 3:30pm, Rutgers University, Hill 705
Tom Benhamou, Rutgers
The Tukey order on ultrafilters, the Galvin property, and the Ultrapower Axiom



Logic and Metaphysics Workshop
Date: Monday, Sept 11, 4.15-6.15pm (NY time)
Room: Philosophy Program Thesis Room (in 7113)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Francesco Paoli, Cagliari
Title: Logical metainferentialism

Abstract: Logical inferentialism is the view that the meaning of the logical constants is determined by the rules of inference that govern their behaviour in proofs – in particular, sequent calculus proofs, according to the preferences of several recent authors. When it comes to the nuts and bolts, however, the view is tenable only if certain aspects – concerning e.g. harmony criteria for rules, normal forms, or proof-theoretic validity – are clarified. Sequent calculus inferentialists generally do so in terms of proofs from axioms, not of derivations from assumptions. Although the merits of this approach are already debatable in traditional settings, recent work on sequent calculi without Identity or Cut has revealed further shortcomings. Logical metainferentialism revises inferentialism in this more general perspective. In this talk, we will sketch the basics of this view and argue that, from this vantage point, the claim that LP is the “One True Logic” may appeal even to the inferentialistically inclined logician.


- - - - Tuesday, Sep 12, 2023 - - - -



- - - - Wednesday, Sep 13, 2023 - - - -



- - - - Thursday, Sep 14, 2023 - - - -



- - - - Friday, Sep 15, 2023 - - - -

NO CLASSES - Rosh Hashanah



Next Week in Logic at CUNY:

- - - - Monday, Sep 18, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, Sept 18, 4.15-6.15pm (NY time)
Room: Philosophy Program Thesis Room (in 7113)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Will Nava (NYU)
Title: Non-classicality all the way up

Abstract: Nearly all non-classical logics that have been studied admit of classical reasoning about them. For example, in the logic K3, A or not-A is not a valid schema. However, ‘A or not-A’ is K3-valid or not K3-valid—this is, in some sense, a valid claim. In this talk, I introduce a simple framework for thinking about the logic of a given logic. This allows for a measure of the non-classicality of a logic—one on which almost all familiar non-classical logics are of the lowest grade of non-classicality. I’ll then discuss some strategies for generating and theorizing logics of higher grades of non-classicality, as well as some motivation for taking these logics seriously.




- - - - Tuesday, Sep 19, 2023 - - - -



- - - - Wednesday, Sep 20, 2023 - - - -



- - - - Thursday, Sep 21, 2023 - - - -



- - - - Friday, Sep 22, 2023 - - - -

Model Theory Seminar
CUNY Graduate Center, Room 5383
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Friday, Sept 22, 12:30-2:00pm
Michael Benedikt, University of Oxford
TBA




Logic Workshop
CUNY Graduate Center
Friday Sept 22, 2:00pm-3:30pm, Room 6417

David Marker, University of Illinois at Chicago
On equations of Poizat type

We look at differential equations of the form  where  is a rational function over the field of constants. We characterize when such equations are strongly minimal and study algebraic relations between solutions to two such equations.





- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday September 13th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- P-measures without P-points, part 2 We will finish the construction of a model with p-measures and no p-points. We also present an example, due to P. Borodulin-Nadzieja, of a p-measure whose construction does not rely on the existence of p-points in any way. Best, David

Logic Seminars next week

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore FIRST TALK: Date: Tuesday, 12 September 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-06. Speaker: Borisa Kueljevic Title: L:ower bounds of sets of P-points Abstract: We will sketch the proof that MA(kappa) implies that each collection of P_c-points of size at most kappa which has a P_c-point as an RK upper bound also has a P_c-point as an RK lower bound. This is joint work with Dilip Raghavan and Jonathan Verner. SECOND TALK: Date: Thursday 14 September 2023, 17:00 hrs Place: Department of Mathematics, Room S17#04-06. Speaker: Jan Dobrowolski Title: Kim-independence in positive logic Abstract: The class of NSOP1 theories, originally introduced by Dzamonja and Shelah in 2004, has been studied very intensively in the last few years since the striking discovery of an independence relation called Kim-independence by Ramsey and Kaplan (based on earlier ideas of Kim and a work of Chernikov and Ramsey), which generalises forking independence in simple theories, and retains almost all its nice properties in the class of NSOP1 theories. I will start the talk with an overview of the notion of Kim-independence, and then I will present my joint work with Mark Kamsma on generalising Kim-independence to positive logic. In particular, I will discuss examples of positive NSOP1 theories falling into our framework such as the theory of existentially closed exponential fields (studied by Kirby and Haykazyan), the theory of fields with a generic submodule (studied by d'Elbee, Kaplan and Neuhauser) and the hyperimaginary extensions of NSOP1 theories. URL OF LOGIC SEMINAR: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Logic Seminar Today

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Tuesday, 5 September 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-06 Speaker: Sun Mengzhou Title: On the (non)elementarity of cofinal extension Abstract: Compared with end extensions, much little is known about cofinal extensions for models of fragments of PA. In particular, it is not even known known whether the elementarity of cofinal extensions can fail at some specific level. In this talk, I will try to give a complete answer. I will present a systemetic way to `compress' the truth of M into the second-order structure of a definable cut, and as a consequence, a correspondence theorem between the first-order theory of M and the second-order theory of the cut. Through this method I will construct several models with special cofinal extension properties. I will also show that every countable model of arithmetic fail to satisfy PA admits a non-elementary cofinal extension. It provides a model-theoretic characterization for PA in terms of cofinal extensions. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

This Week in Logic at CUNY
Welcome back, everyone!  Regular weekly mailings will continue through the start of winter break (late December).  Heads up - as usual, there are a number of three-day weekends in September, including the current Labor Day weekend.  Hope you are enjoying it.

Best,
Jonas Reitz



This Week in Logic at CUNY:

- - - - Monday, Sep 4, 2023 - - - -

COLLEGE CLOSED - Labor Day

- - - - Tuesday, Sep 5, 2023 - - - -



- - - - Wednesday, Sep 06, 2023 - - - -



- - - - Thursday, Sep 07, 2023 - - - -



- - - - Friday, Sep 08, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday Sept 8, 2:00pm-3:30pm, Room 6417

Hans Schoutens, CUNY
The model-theory of compact spaces

A more correct title would read: the model-theory of the category of compact (Hausdorff) spaces. Last year, I gave a talk about the model-theory of categories, and this talk will be its continuation (but I will repeat everything that is relevant) in which I will look at one special case: COMP, the category of compact spaces. Let C be any model that is elementary equivalent to the category COMP (but if you’re a standard guy, you can just take C=COMP and everything is still interesting). The model C 'remembers' the topology of each of its objects (except we might have lost compactness). But it can recover much more, to an extent that I would almost call it 'foundational'. I will show how to reconstruct a model of PA, a model of the ORD (ordinals) and even a model of ZFC. If you wonder, which model of ZFC you get if you just start with COMP, the answer is: the same you woke up to this morning!



Next Week in Logic at CUNY:

- - - - Monday, Sep 11, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, Sept 11, 4.15-6.15pm (NY time)
The room is yet to be determined. Meetings will be face to face only.
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Francesco Paoli, Cagliari
Title: Logical metainferentialism

Abstract: Logical inferentialism is the view that the meaning of the logical constants is determined by the rules of inference that govern their behaviour in proofs – in particular, sequent calculus proofs, according to the preferences of several recent authors. When it comes to the nuts and bolts, however, the view is tenable only if certain aspects – concerning e.g. harmony criteria for rules, normal forms, or proof-theoretic validity – are clarified. Sequent calculus inferentialists generally do so in terms of proofs from axioms, not of derivations from assumptions. Although the merits of this approach are already debatable in traditional settings, recent work on sequent calculi without Identity or Cut has revealed further shortcomings. Logical metainferentialism revises inferentialism in this more general perspective. In this talk, we will sketch the basics of this view and argue that, from this vantage point, the claim that LP is the “One True Logic” may appeal even to the inferentialistically inclined logician.


- - - - Tuesday, Sep 12, 2023 - - - -



- - - - Wednesday, Sep 13, 2023 - - - -



- - - - Thursday, Sep 14, 2023 - - - -



- - - - Friday, Sep 15, 2023 - - - -

NO CLASSES - Rosh Hashanah




- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
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(KGRC) talks for the upcoming semester

Kurt Godel Research Center
The KGRC welcomes as guests: David Schrittesser visits the KGRC until September 14. Lou van den Dries visits the KGRC until September 15. Andreas Weiermann visits the KGRC on September 14 and gives a talk, see below. * * * Logic Colloquium Kurt Gödel Research Center Thursday, September 14 "Phase transitions for Gödel incompleteness" Andreas Weiermann (Ghent University, BE) In the first part we will survey several results regarding the provability/unprovability thresholds for natural assertions which are independent of the Peano axioms. In the second part we will present some recent findings regarding the phase transition for Friedman's version of the Bolzano Weierstrass theorem. These findings answer a question by Harvey M. Friedman. Time and Place Talk at 1:30pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! For further information, please write to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, October 5 Thursday, October 12 Thursday, October 19 Thursday, November 9 Thursday, November 16 Thursday, November 23 Mini-course: "Convergence in Banach spaces of measures and cardinal characteristics of the continuum" Damian Sobota (KGRC) During this mini-course I will show how various properties of Banach spaces of measures (on compact spaces or Boolean algebras) are affected by values of the cardinal characteristics of the continuum occuring in Cichoń's diagram and van Douwen's diagram. We will in particular be interested in convergence properties of sequences of measures in weak* and weak topologies. Besides, we will study what impact extending the set-theoretic universe by forcing can have on topologies of ground model Banach spaces of measures. Finally, I will present connections between convergence of measures on compact spaces and filters on countable sets. Time and Place Talks at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the respective talk, please contact richard.springer@univie.ac.at! For further information, please write to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, November 30 Thursday, December 7 Thursday, December 14 Thursday, January 11 Thursday, January 18 Thursday, January 25 Mini-course: "Forcing techniques for Cichoń's Maximum" Diego Alejandro Mejía (Shizuoka University, JP) Cichoń's diagram describes the connections between combinatorial notions related to measure, category, and compactness of sets of irrational numbers. In the second part of the 2010's decade, Goldstern, Kellner and Shelah constructed a forcing model of Cichoń's Maximum (meaning that all non-dependent cardinal characteristics are pairwise different) by using large cardinals. Some years later, we eliminated this large cardinal assumption. In this mini-course, we explore the forcing techniques to construct the Cichoń's Maximum model and much more. Concretely, we discuss the following components: 1. Tukey connections and cardinal characteristics of the continuum 2. Review of FS (finite support) iterations and basic methods to modify cardinal characteristics. 3. Preservation theory for cardinal characteristics. 4. FS iterations with measures and ultrafilters on the natural numbers. 5. Boolean Ultrapowers. 6. Forcing Intersected with submodels. Time and Place Talks at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the respective talk, please contact richard.springer@univie.ac.at! For further information, please write to vera.fischer@univie.ac.at.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday September 6th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- P-measures without P-points We will prove that consistently there are P-measures but no P-point exists. Best, David

Logic Seminar 5 Sept 2023 17:00 hrs at NUS by Sun Mengzhou

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Tuesday, 5 September 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-06 Speaker: Sun Mengzhou Title: On the (non)elementarity of cofinal extension. Compared with end extensions, much little is known about cofinal extensions for models of fragments of PA. In particular, it is not even known known whether the elementarity of cofinal extensions can fail at some specific level. In this talk, I will try to give a complete answer. I will present a systemetic way to `compress' the truth of M into the second-order structure of a definable cut, and as a consequence, a correspondence theorem between the first-order theory of M and the second-order theory of the cut. Through this method I will construct several models with special cofinal extension properties. I will also show that every countable model of arithmetic fail to satisfy PA admits a non-elementary cofinal extension. It provides a model-theoretic characterization for PA in terms of cofinal extensions. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Logic Seminar 29 Aug 2023 17:00 hrs at NUS by Tran Chieu Minh

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Tuesday, 29 August 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-06 Speaker: Tran Chieu Minh Title: Measure doubling of small sets in SO(3,R) Abstract: In a recent work, we show that if A is an open subset of SO(3,R) with sufficiently small normalized Haar measure, then mu(A^2) > 3.99 mu(A). This was conjectured by Emmanuel Breuillard and Ben Green around 15 years ago in the context of getting optimal bounds and finding continuous counterparts of product theorems by Helfgott, Pyber-Szabo, and Breuillard-Green-Tao. The result is also related to the Brunn-Minkowski inequalities from convex geometry, the Kunze-Stein phenomenon from harmonic analysis, and the Pillay conjectures from model theory. In this talk, I will explain these connections and discuss some ideas from the proof, which uses nonstandard analysis and neostable group theory. (The talk is based on joint work with Yifan Jing and Ruixiang Zhang) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Fwd: Aviles

Wrocław Set Theory Seminar


---------- Forwarded message ---------
Od: Grzegorz Plebanek <grzegorz.plebanek@math.uni.wroc.pl>
Date: czw., 24 sie 2023 o 20:39
Subject: Aviles
To: Piotr Borodulin-Nadzieja <pborod@math.uni.wroc.pl>, Szymon Żeberski <szymon.zeberski@pwr.edu.pl>, Paweł Krupski <pawel.krupski@pwr.edu.pl>, Robert Rałowski <robert.ralowski@pwr.edu.pl>, Maciej Korpalski <Maciej.Korpalski@math.uni.wroc.pl>, Arturo Antonio Martínez Celis Rodríguez <amartinezcelis@gmail.com>, <sebastian.jachimek@math.uni.wroc.pl>, Tomasz Żuchowski <tomasz.artur.zuchowski@gmail.com>


Panowie (Arturo: please use translator:-)
Antonio Aviles będzie  w IM UWR cały przyszły tydzień. 
Rysuje się idea  niezbyt formalnego seminarium we wtorek 29 sierpnia.
i jego odczyt (pod tytułem News from Murcia...)
Proponuje spotkać się na kawie w IM UWr o 16.00 i zacząć ok 16.20, a następnie udać się do pobliskiej restauracji (ok. 18.30). Wszystko trochę wcześniej niż zwykle- w IM trudniej wejść późnym wieczorem).
Dajcie mi e-mailem, proszę znać, kto będzie miał ochotę przyjść i, przede wszystkim,  kto wybierze się z nami na kolację (zapewne kuchnia azjatycka).
Szymonie, prześlij wiadomość. osobom, które pominąłem; nie mam wszystkich adresów.
Pozdrawiam, G

Wednesday seminar

Prague Set Theory Seminar
Dear all, There is no seminar next week (Wednesday August 30th). Instead, you may want to sneak in to the talk of Oleg Pikhurko -- Measurable Combinatorics which takes place on Wednesday at 9:00 at the Eurocomb conference at Mala Strana. https://iuuk.mff.cuni.cz/events/conferences/eurocomb23/program.html Mostly regular Wednesday seminars will resume in September. Best, David

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday August 23rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Ultracoherence We will present some results about the existence of nontrivial coherent families of functions, focusing especially on families indexed by ultrafilters. In the process, we will discuss some connections with forcing axioms, partition principles, and Čech-Stone compactifications of discrete spaces. Best, David

Wednesday seminar

Prague Set Theory Seminar
Dear all, Very likely there will be no Wednesday seminar the next and a couple of following weeks. I will send an announcement once we start meeting again (mid August--September). Also, in the meantime, let me know in case there would be a good reason for the seminar to meet -- an interesting guest visiting Prague, an interesting result you want to share,.. Best, David

Wednesday seminar

Prague Set Theory Seminar
Dear all, A quick update. This Wednesday July 12th we will have Pedro H. Zambrano giving a talk. https://sites.google.com/a/unal.edu.co/phzambranor/home I don't have the title/abstract of the talk yet, I will post it online once I get it. Here; https://calendar.math.cas.cz/seminar-on-reckoning-actual Also, we are moving to the air-conditioned room again. The seminar meets on Wednesday July 12th at 11:00 in the Institute of Mathematics CAS, Zitna 25, blue lecture hall, ground floor, rear building. Best, David On 09/07/2023 08:06, David Chodounsky wrote: > Dear all, > > The seminar meets on Wednesday July 12th at 11:00 in the Institute of > Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. > > There is no fixed program yet. The plan is to do some ad hoc interesting > mathematics. > > > Best, > David

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday July 12th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There is no fixed program yet. The plan is to do some ad hoc interesting mathematics. Best, David

RIMS Set Theory Workshop: October 24-27, 2023

Conference
We are pleased to announce RIMS Set Theory Workshop 2023. This year's workshop will be held in a hybrid format of in-person at RIMS, Kyoto University, and online via Zoom. RIMS Set Theory Workshop 2023 - Large Cardinals and the Continuum - dates: Tue 24 Oct — Fri 27th Oct, 2023 venue: RIMS, Kyoto University, Japan & Online via Zoom organizer: Hiroshi Fujita (Ehime) contact: fujita.hiroshi.mh@ehime-u.ac.jp web page: https://tenasaku.com/RIMS2023/ We will have a mini-course by Joan Bagaria (Barcelona). Call for Contribution: We encourage both young researchers and experts to contribute with talks. Any topics in Set Theory and relevant areas are welcome. Both in-person talks at RIMS and online talks via Zoom are welcome. If you would like to give a talk at the workshop, please let us know by Fri 8 Sep, via Email to the organizer. Call for Participation: If you would like to participate in-person (at RIMS), please let us know by Fri 29 Sep, via Email to the organizer. If you would like to participate online (via Zoom), please let us know by Fri 15 Oct, via Email to the organizer. We are looking forward to your participation!
Link to more info

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday June 28th at 11:00 in the Institute of Mathematics CAS, Zitna 25, blue lecture hall, ground floor, rear building. NOTE THE LOCATION CHANGE! Also let remind you the PhD defense of David Uhrik on Thursday afternoon next week (online only), and the restaurant visit (in person) which will follow. If you are interested in taking part, get in touch. Program: Jindrich Zapletal -- Fraisse limits and permutation models of ZF I introduce a new rich class of relational Fraisse structures. Their automorphism group admits detailed classification of its open subgroups, and their associated permutation model of ZF admits detailed study as well. Best, David

(KGRC) two talks on Thursday, June 29

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy visits the KGRC until August 15. Thilo Weinert visits the KGRC until June 30. Serhii Bardyla visits the KGRC from June 24 to July 2. Yurii Khomskii visits the KGRC from June 27 to July 1. David Schrittesser visits the KGRC from June 30 to September 14. Aristotelis Panagiotopoulos visits the KGRC from July 10 to July 25. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, June 29 "Spectra of combinatorial families" Lukas Schembecker (KGRC) I will give a brief overview of theory of the possible spectra of various combinatorial families such as mad families, independent families and other similar families. In particular I will detail the proof that there are no mad families of intermediate size in the Cohen model as an introduction to isomorphism-of-names arguments. Finally, I will sketch recent work of how to realise uncountable spectra of a_T, i.e. given an uncountable set C of cardinals (with some necessary extra assumptions) how to construct a model which has partitions of Baire space into compact sets of exactly the sizes prescribed in C. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, June 29 "Coloring universal pseudotrees" Monroe Eskew (KGRC) A pseudotree a set-theoretic tree without well-foundedness requirement; it is a partial order that is linear below any element. Assuming \kappa^{<\kappa} = \kappa, there is a definable pseudotree of size \kappa that contains a copy of every pseudotree of size \kappa. This pseudotree has the property that for every coloring of its nodes in finitely many colors, there is a monochromatic subtree isomorphic to the original one. We will sketch proofs of the above facts (which will be elementary and involve pictures) and discuss what we know about coloring pairs (where the situation is quite different). This is joint work with Thilo Weinert and David Chodounsky. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at.

Nankai Logic Colloquium

Nankai Logic Colloquium
Hello everyone,

The 2022-2023 school year is about to end. Yesterday we held the last Nankai Logic Colloquium for this semester. Thank you for attending!

Nankai Logic Colloquim is going to be resumed next semester. See you next semester!

P.S. Next semester there is going to be a major event in math logic held in Tianjin organized by Nankai University: the Asian Logic Conference! Follow this link for more details: https://logic.nankai.edu.cn/alc2023/main.htm

Best wishes,
Ming Xiao

(KGRC) two talks on Tuesday, June 20 and two talks on Thursday, June 22

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy visits the KGRC until August 15. Thilo Weinert visits the KGRC until June 30. Jaroslav Supina visits the KGRC from June 18 to June 24. Serhii Bardyla visits the KGRC from June 24 to July 2. David Schrittesser visits the KGRC from June 30 to September 14. * * * Set Theory Seminar Kurt Gödel Research Center Tuesday, June 20 "Preservation results related to finitely additive measures on Boolean algebras" Diego Mejía (Shizuoka University, JP) Kamburelis (1989) proved that Boolean algebras with finitely additive measures preserve "strong witnesses" of the additivity of measure, which is one of the ingredients in the proof of Cichoń's maximum (forcing a constellation where all non-dependant entries in Cichoń's diagram are pairwise different). Based on Kamburelis' results, we present a generalization of the previous preservation result by taking away the "finitely additive measure" requirement. On the other hand, we give one example where a special property on the finitely additive measure gives the preservation of the additivity of the strong measure ideal, and also develop its corresponding preservation theory that doesn't rely on finitely additive measures. This strengthens preservation results by Judah and Shelah (1989). This is a joint work with Jörg Brendle and Miguel Cardona. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Tuesday, June 20 "Combinatorial Banach spaces" Sebastian Jachimek (University of Wrocław, PL) A combinatorial space is a Banach space induced by some family of subsets of natural numbers. During the talk I will present examples of such families and the appropriate Banach spaces. Furthermore, I will consider properties of those spaces, in particular in the context of containing isomorphic copies of the standard sequential Banach spaces $c_0$ and $\ell_1$. Time and Place Talk at 4:45pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 2nd floor Seminar room 18 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, June 22 "Katětov power ideals and the Fréchet-Urysohn property" Jaroslav Šupina (University of Košice, SK) At the beginning of the 1970s, M. Katětov discovered that iterated Fubini products of the Fréchet filter play a crucial role in the theory of Baire classes of functions. Recently, it has been shown that the transfinitely iterated Fréchet ideals are critical for maximal almost disjoint families or Ellentuck spaces. We show that these ideals fit well with the specific hierarchy of topological spaces related to delta-sets. Consequently, we get a solution to two problems on the Fréchet-Urysohn property of function spaces. This is a joint work with S. Bardyla and L. Zdomskyy. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, June 22 "Uniform Factoring for Operator Ideals" Kevin Beanland (Washington & Lee University, US) Beginning with the work of Jean Bourgain and later the Ph.D. thesis of Benoit Bossard, researchers have been using notions and methods of descriptive set theory to provide remarkable embedding results for classes of separable Banach spaces. More recently by considering a natural coding of the class of bounded linear operators between separable Banach spaces, many of these embedding results have been generalized to factorization results for operators; especially uniform factorization results for subsets of operator ideals. In this talk, I will explain this framework, outline some recent achievements in the area, and give avenues for future research. The work presented can be found in several papers written jointly with several coauthors including Ryan Causey, Dan Freeman, Bruno Braga, and Leandro Antunes. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday June 21st at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. On Wednesday June 28th we should have a seminar talk by Jindrich Zapletal, Wednesday July 5th is a state holiday -> no seminar. Seminars during July and August are TBD. David Uhrik will be defending his PhD thesis on Thursday June 29th. The defense is online only, starts at 15:30. https://is.cuni.cz/studium/eng/szz/index.php?do=detail&ffak=11320&ftyp=&kom=57302&term=778490 I assume after the defense we will go for a dinner/beer/coffee somewhere in the city center. Get in touch in case you are interested either in the defense Zoom link and/or in the event afterwards. Program (next week): Chris Lambie-Hanson -- Indecomposable ultrafilters and their utility The notion of "indecomposability" of an ultrafilter is a natural weakening of the notion of "completeness". Unlike countably complete nonprincipal ultrafilters, nontrivially indecomposable ultrafilters can consistently exist on relatively small cardinals (e.g., $\aleph_{\omega+1}$), yet indecomposable ultrafilters entail many of the same compactness principles as complete ultrafilters. In this talk, we will present some classical and some recent results on the existence of indecomposable ultrafilters and applications thereof. Depending on time and interest of the audience, these applications may involve tightness of topological spaces, partition relations, and compactness for chromatic numbers of graphs. The talk will include joint work with Jeffrey Bergfalk and Jing Zhang. Best, David

Conferencias del Seminario Colombo Mexicano de Teoría de Conjuntos 2023-I.

Seminario Colombo Mexicano de Teoría de Conjuntos
Seminario Colombo Mexicano de Teoría de Conjuntos

Cordial saludo a cada miembro del Grupo de Lógica de Bogotá.

Compartimos con ustedes un enlace de youtube donde podrán encontrar los videos de todas las sesiones del Seminario Colombo Mexicano de Teoría de Conjuntos que tuvimos durante el primer semestre del 2023. Allí también se encuentran los videos de las sesiones del año pasado.

Aprovechamos para agradecer a conferencistas y asistentes por la participación en el seminario durante este semestre, y los invitamos a continuar participando activamente en el seminario el próximo semestre.

Cordialmente:

Julián C. Cano (jc.canor@uniandes.edu.co). Universidad de los Andes, Bogotá.

Francisco S. Nieto (francisco.s.nieto@ciencias.unam.mx). Universidad Nacional Autónoma de México, Morelia.


Enlace de las conferencias:




 

(KGRC) TU Wien Mini Workshop and two KGRC talks

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Thilo Weinert (host: Vera Fischer) visits the KGRC until June 30. Ido Feldman (host: Miguel Moreno) visits the KGRC until June 17 and gives two talks, one at the TU Wien Mini Workshop and one at U Wien, details for both are below. Jindřich Zapletal (host: Vera Fischer) visits the KGRC from June 14 to June 16 and gives a talk, see below. Jaroslav Šupina (host: Vera Fischer) visits the KGRC from June 18 to June 24 and gives a talk, details to be announced at a later time. Serhii Bardyla (host: Vera Fischer) visits the KGRC from June 24 to July 2. David Schrittesser (host: Vera Fischer) visits the KGRC from June 30 to September 14. * * * We are happy to relay a message from Sandra Müller and Takehiko Gappo: TU Wien Mini Workshop in Set Theory on June 12 TU Wien Mini Workshop in Set Theory will take place on June 12 at Technical University of Vienna. There will be 6 talks given by the following speakers. - Lena Wallner (TU Wien) - William Chan (University of North Texas) - Ido Feldmann (Bar-Ilan University) - Adam Kwela (University of Gdańsk) - Dominik Adolf (Bar-Ilan University) - Bartosz Wcisło (University of Gdańsk) Given the limited seating capacity of the venue and arrangements for catering, we kindly request you to inform Takehiko Gappo (takehiko.gappo@tuwien.ac.at) in advance of your intention to attend. There is no registration fee. See the webpage for further information: https://sites.google.com/view/takehikogappo/conferences/tu-wien-mini-workshop We have decided to livestream the talks through Zoom! Please inform Takehiko Gappo if you would like to get the link. If you have any questions, please contact us at takehiko.gappo@tuwien.ac.at or sandra.mueller@tuwien.ac.at. Best regards, Takehiko Gappo and Sandra Müller * * * Set Theory Seminar Kurt Gödel Research Center Thursday, June 15 "Sums of triples in Abelian groups" Ido Feldman (Bar-Ilan University, IL) In 1974, Hindman proved that considering the semigroup $(\mathbb{N},+)$, for any partition $\mathbb{N} = S_0 \uplus S_1$, there exists an infinite $X \subseteq \mathbb{N}$ such that the set of its finite sums, is monochromatic, that is, contained in one of the cells. In contrast, in 2016 Komjáth showed that, for the group $(\mathbb{R}, +)$ there exists a partition $\mathbb{R} = S_0 \uplus S_1$ such that, whenever $X \subseteq \mathbb{R}$ is uncountable, not only is the set of finite sums not monochromatic, but already the set $\mathrm{FS}_2(X) := \{x + y | \{x, y\} \in [X]^2\}$ is not monochromatic. These results motivate a general investigation of additive Ramsey theory in the spirit of the classical partition calculus, and which in fact for some cases are a strengthening of the classical partition calculus. Motivated by similar problems at the level of $\aleph_2$, we extend Todorčević’s partition of three-dimension combinatorial cube to handle additional three dimensional objects. As a corollary we prove that the failure of continuum hypothesis asserts that for every Abelian group $G$ of size $\aleph_2$, there exist a coloring $c : G \to \mathbb{Z}$ such that, for every uncountable $X \subseteq G$ and every integer $k$, there exist three distinct elements $x, y, z \in X$ such that $c(x, y, z) = k$. This is a joint work with Assaf Rinot. For further reading the article is available here: https://londmathsoc.onlinelibrary.wiley.com/doi/10.1112/mtk.12200 Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, June 15 "Group dynamics and models of ZF" Jindřich Zapletal (University of Florida, US) I will develop basics of the theory of permutation models of set theory with emphasis on the dialog between their internal features and dynamical properties of the underlying group action. There are many novel, clean theorems connecting fragments of the axiom of choice with group theory and dynamics. As an initial example, if the acting group is abelian, in the resulting permutation model every set is a union of a well-orderable collection of well-orderable sets. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at.

Cross-Alps Logic Seminar (speaker: André Nies)

Cross-Alps Logic Seminar
On Friday 16.06.2023 at 16.00
André Nies (University of Auckland)
will give a talk on 
Computably totally disconnected, locally compact groups

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Vincenzo

Set Theory and Topology Seminar 13.06.2023 Paweł Krupski

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology (on Tuesday 06.06.2023 at 17:15 in room A.4.1 C-19  (Wrocław University of Science and Technology) the lecture:
"Remarks and questions on hyperspaces of knots: Borel complexity and local contractibility"
will be presented by

Paweł Krupski


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)


About 15 minutes before the seminar we invite you for coffee and a chat to social room A.4.1.A in C-19. 

After the (last in this semester) seminar, we plan to continue informally at Liquid Form :)

*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Shaun Allison from the University of Toronto. This talk is going to take place this Friday,  June 9th,  from 9am to 10am(UTC+8, Beijing time). 

Title: Countable treeable Borel equivalence relations are classifiable by $\ell_1$.

Abstract: A celebrated result of Gao-Jackson is that every equivalence relation induced by a Borel action of a countable abelian group is hyperfinite. Greg Hjorth asked if indeed every countable Borel equivalence relation that is Borel-reducible to an orbit equivalence relation induced by an abelian Polish group is hyperfinite. We prove that while the answer to Hjorth's question is "yes" in many situations, in fact every countable treeable Borel equivalence relation is classifiable by an abelian Polish group. Given that the free part of the Bernoulli shift action of F_2 is treeable but not hyperfinite, this answers Hjorth's question in the negative in general. The proof relies on a subtle property of a treeing which we call "stretched", as well as a free Banach space construction. We will spend much of the time explaining the context and all of the relevant definitions behind this result, and then we will give a sketch of the proof. We end with some suggestions for future directions.


__________________________________________________________________________________________________

Title :The 32nd Nankai Logic Colloquium --Shaun Allison

Time :9:00am, Jun. 9, 2023(Beijing Time)

Zoom Number :893 1745 8343

Passcode : 283146

Link :https://us02web.zoom.us/j/89317458343?pwd=L01Hc28yc0J2OGk3c3VPS3gvVjVndz09

_____________________________________________________________________


Best wishes,

Ming Xiao





Cross-Alps Logic Seminar (speaker: Ulrich Kohlenbach)

Cross-Alps Logic Seminar
On Friday 09.06.2023 at 16.00
Ulrich Kohlenbach (Technische Universität Darmstadt)
will give a talk on 
Proof mining: Recent developments

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Vincenzo

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Dominik Kwietniak from Jagiellonian University. This talk is going to take place this Friday,  June 2nd,  from 4pm to 5pm(UTC+8, Beijing time). 

Title: An anti-classification theorem for the topological conjugacy
problem for Cantor minimal systems

Abstract:
The isomorphism problem in dynamics  dates back to a question of von
Neumann from 1932: Is it possible to classify (in some reasonable
sense) the ergodic measure-preserving diffeomorphisms of a compact
manifold up to isomorphism? We would like to study a similar problem:
let C be the Cantor set and let Min(C) stand for the space of all
minimal homeomorphisms of the Cantor set. Recall that a Cantor set
homeomorphism T is in Min(C) if every orbit of T is dense in C.  We
say that S and T in Min(C) are topologically conjugate if there exists
a Cantor set homeomorphism h such that Sh=hT. We prove an
anti-classification result showing that even for very liberal
interpretations of what a "reasonable'' classification scheme might
be, a classification of minimal Cantor set homeomorphism up to
topological conjugacy is impossible. We see is as a consequence of the
following: we prove that the topological conjugacy relation of Cantor
minimal systems TopConj treated as a subset of Min(C) x Min(C) is
complete analytic. In particular, TopConj is a non-Borel subset of
Min(C) x Min(C). Roughly speaking, it means that it is impossible to
tell if two minimal Cantor set homeomorphisms are topologically
conjugate  using only a countable amount of information and
computation.

Our result is proved by applying a Foreman-Rudolph-Weiss-type
construction used for an anti-classification theorem for ergodic
automorphisms of the Lebesgue space. We find a continuous map F from
the space of all subtrees over non-negative integers N with
arbitrarily long branches into the class of minimal homeomorphisms of
the Cantor set. Furthermore, F is a reduction, which means that a tree
T is ill-founded if and only if F(T) is topologically conjugate to its
inverse. Since the set of ill-founded trees with arbitrarily long
branches is a well-known example of a complete analytic set, we see
that it is essentially impossible to classify which minimal Cantor set
homeomorphisms are topologically conjugate to their inverses.

This is joint work with Konrad Deka, Felipe García-Ramos, Kosma
Kapsrzak, Philipp Kunde (all from the Jagiellonian University in
Kraków).

__________________________________________________________________________________________________

Title :The 31st Nankai Logic Colloquium --Dominik Kwietniak

Time :16:00pm, Jun. 2, 2023(Beijing Time)

Zoom Number : 876 3579 6414

Passcode : 318535

Link :https://us02web.zoom.us/j/87635796414?pwd=M1hZSEFvL0FzMUZQcHVCQ0w2QlhtUT09

_____________________________________________________________________


Best wishes,

Ming Xiao





Set Theory and Topology Seminar 6.06.2023 Piotr Szewczak (UKSW)

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology (on Tuesday 06.06.2023 at 17:15 in room A.4.1 C-19  (Wrocław University of Science and Technology) the lecture:
"Totally imperfect Menger sets"
will be presented by

Piotr Szewczak (UKSW)


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)


Abstract

A set of reals X is Menger if for any countable sequence of open covers of X one can pick finitely many elements from every cover in the sequence such that the chosen sets cover X. Any set of reals of cardinality smaller than the dominating number d is Menger and there is a non-Menger set of cardinality d. By the result of Bartoszyński and Tsaban, in ZFC, there is a totally imperfect (with no copy of the Cantor set inside) Menger set of cardinality d. We solve a problem, whether there is such a set of cardinality continuum. Using an iterated Sacks forcing and topological games we prove that it is consistent with ZFC that d<c and each totally imperfect Meneger set has cardinality less or equal than d.
This is a joint work with Valentin Haberl and Lyubomyr Zdomskyy.
The research was funded by the National Science Centre, Poland  and the Austrian Science Found under the Weave-UNISONO call in the Weave programme, project: Set-theoretic aspects of topological selections 2021/03/Y/ST1/00122.


About 15 minutes before the seminar we invite you for coffee and a chat to social room A.4.1.A in C-19. 


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Liuzhen Wu from the Academy of Mathematical and Systems Sciences, CAS. This talk is going to take place this Friday,  May 26th,  from 4pm to 5pm(UTC+8, Beijing time). 


title: Definability of the nonstationary ideal on $\omega_1$

abstract: The nonstationary ideals are natural nontrivial ideals defined on all uncountable regular cardinals. In this talk, various aspects of definability of nonstationary ideals on uncountable cardinals are explored. The main focus is  the definability of nonstationary ideal on $\omega_1$ ($NS_{\omega_1}$ for short) in some canonical models of set theory. In particular, under MM or (*) axiom, $NS_{\omega_1}$ is not $\Pi_1$ definable. On the other hand, it is consistent that in some model of $PFA$, $NS_{\omega_1}$ is $\Pi_1$ definable. This is based on the accumulated work of Aspero, Hoffelner, Larson, Schindler, Sun, Wu.

__________________________________________________________________________________________________

Title : The 30th Nankai Logic Colloquium --Liuzhen Wu

Time :16:00pm, May. 26, 2023 (Beijing Time) 

Zoom Number : 851 5601 8255

Passcode : 136440

Link :https://us02web.zoom.us/j/85156018255?pwd=UjFUb3cwT0poY0JYakRub2kyNGdSdz09

_____________________________________________________________________


Best wishes,

Ming Xiao





Set Theory and Topology Seminar 30.05.2023 Zbigniew Lipecki

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology (on Tuesday 30.05.2023 at 17:15 in room A.4.1 C-19  (Wrocław University of Science and Technology) the lecture:
"How noncompact is the space of Lebesgue measurable functions?"
will be presented by

Zbigniew Lipecki (IM PAN)


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)


Abstract

The space in question is the space $\textfrak M$ of Lebesgue measurable subsets of the unit interval equipped with the usual Fr'echet--Nikodym (semi)metric. We show that there exists a sequence of elements of $\textfrak M$ such that their mutual distances are > 1/2. It seems to be an open problem whether "1/2" can be replaced here by a bigger constant C. We show that C must be smaller than 9/14. Moreover, we present a version of the problem in terms of binary codes.


About 15 minutes before the seminar we invite you for coffee and a chat to social room A.4.1.A in C-19. 


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Charla de Justin Moore en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

May 25

4:00 p.m. - 5:00 p.m. (Colombia time)  


Large minimal non-$\sigma$-scattered orders
Justin T. Moore
Cornell University

Abstract. We present new constructions of linear orders which are minimal with respect to being non-$\sigma$-scattered. Specifically, we will show that Jensen's diamond principle implies that there is a minimal Countryman line, answering a question of Baumgartner. We will also construct the first consistent examples of minimal non-$\sigma$-scattered linear order of cardinality greater than $\aleph_1$. In fact, this can be achieved at any successor cardinal $\kappa^+$, both via forcing constructions and via axiomatic principles which hold in Gödel's Constructible Universe. These linear order of cardinality $\kappa^+$ have the property that their square is the union of $\kappa$-many chains. 
This is joint work with James Cummings and Todd Eisworth.

Zoom meeting information.

Meeting ID: 856 1882 0721

Passcode: 123456

https://cuaieed-unam.zoom.us/j/85618820721


This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

This will be the final edition of "This Week in Logic" for the Spring 2023 semester.  Regular mailings will resume in late August.  We will send out special editions for events over the summer - please send me your notifications.

Be well,
Jonas


This Week in Logic at CUNY:

- - - - Monday, May 22, 2023 - - - -



- - - - Tuesday, May 23, 2023 - - - -

MAMLS Spring Fling at Rutgers University
The MAMLS Spring Fling meeting will take place May 23-26 at Rutgers University, New Brunswick, New Jersey. More information about the meeting can be found on its website (https://sites.math.rutgers.edu/~fc327/MAMLS2023/index.html). Registration is free and everyone who plans to attend is encouraged to register for logistics purposes.


- - - - Wednesday, May 24, 2023 - - - -



- - - - Thursday, May 25, 2023 - - - -



- - - - Friday, May 26, 2023 - - - -





- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

(KGRC) four talks, long and short

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Thilo Weinert (host: Vera Fischer) visits the KGRC from May 10 to June 30. Sergei Starchenko (host: Matthias Aschenbrenner) visits the KGRC from May 13 to May 27 and gives a talk, see below. Aaron Anderson (host: Matthias Aschenbrenner) visits the KGRC from May 23 to May 24 and gives a talk, see below. Fabian Kaak (host: Vera Fischer) visits the KGRC from May 23 to May 26 and gives a short talk, see below. Nigel Pynn-Coates (host: Matthias Aschenbrenner) visits the KGRC from June 2 to June 10. Ido Feldman (host: Miguel Moreno) visits the KGRC from June 11 to June 17 and gives a talk, details to be announced at a later time. Jaroslav Šupina (host: Vera Fischer) visits the KGRC from June 18 to June 24 and gives a talk, details to be announced at a later time. David Schrittesser (host: Vera Fischer) visits the KGRC from June 30 to September 14. * * * Model Theory Seminar Kurt Gödel Research Center Wednesday, May 24 "Distality in Continuous Logic" Aaron Anderson (University of California, LA, US) We examine distal theories and structures in the context of continuous logic, providing several equivalent definitions. By studying the combinatorics of fuzzy VC-classes, we find continuous versions of (strong) honest definitions and distal cell decompositions. By studying generically stable Keisler measures in continuous logic, we apply the theory of continuous distality to analytic versions of graph regularity. Time and Place Talk at 3:00pm Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, May 25 This installment of the seminar will see two shorter talks: "Set theory of a Suslin line" Fabian Kaak (Universität Kiel, DE) A Suslin line is a linear ordering, which is in some way quite similar to the real line. We will discuss in what ways the set theory of the real line can be adapted to a Suslin line. We give a characterization of Borel sets of the Suslin line, look at a few cardinal characteristics and play games on a Suslin tree. ... as well as ... "Strong Measure Zero Sets on the Higher Cantor Space" Nick Chapman (TU Wien) As introduced by Borel in the early 20th century, a set of reals is strong measure zero if it can be covered by a sequence of intervals whose lengths shrink arbitrarily fast. This notion admits a natural generalisation in the context of the higher Cantor space $2^\kappa$. However, contrasting the situation on $2^\omega$, much about the behaviour of strong measure zero sets on $2^\kappa$ is unknown; in particular, the consistency of Borel's Conjecture in this context ("A set is strong measure zero iff it has size at most $\kappa$") is still open. We shall discuss a statement closely related to the Borel Conjecture: for $\kappa$ inaccessible we will sketch the construction of a model of $|2^\kappa| = \kappa^{++}$ and "$\forall X \subseteq 2^\kappa: X \text{ is strong measure zero iff } |X| \leq \kappa^+$", focusing on some of the difficulties one runs into when generalising proof strategies from the countable case. Time permitting, we will also briefly touch on Halko's notion of stationary strong measure zero sets. The content of this talk is extracted from my Master thesis and is based on earlier work by Johannes Schürz. Time and Place Both talks, one after the other, first talk at 11:30am, in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about these two talks to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, May 25 "On Hausdorff limits of images of o-minimal families in real tori" Sergei Starchenko (University of Notre Dame, US) Let $\{ X_s \colon x\in S \}$ be a family of subsets of ${\mathbb R}^n$ definable in some o-minimal expansion of the real field. Let $\Gamma \subseteq {\mathbb R}^n$ be a lattice and $\pi \colon {\mathbb R}^n/\Gamma \to \mathbb T$ be the quotient map. In a series of papers (published and unpublished) together with Y.Peterzil we considered Hausdorff limits of the family $\{ \pi(X_s) \colon s\in S\}$ and provided their description. In this talk I describe model theoretic tools used in the description. Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at.

Set Theory and Topology Seminar 23.05.2023 Barnabas Farkas

Wrocław Set Theory Seminar
I am happy to announce that at the seminar in Set Theory and Topology (on Tuesday 23.04.2023 at 17:15 in room A.4.1 C-19  (Wrocław University of Science and Technology) the lecture:
"A tool to avoid some technical forcing arguments when working with the Hechler forcing"
will be presented by

Barnabas Farkas (TU Wien)


Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You
Szymon Żeberski

(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski  and myself)


Abstract

I'm going to present that virtually every result saying that finite support iterations of the Hechler forcing preserve a cardinal invariant being small and its dual being large can be reduced to a single preservation theorem. In other words, this theorem eliminates the technical forcing arguments from the proofs of these results and reduces them to easy coding exercises. 

About 15 minutes before the seminar we invite you for coffee and a chat to social room A.4.1.A in C-19. 


*****************************************************************************************************************

Our webpages:
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia

Charla de Alfredo Zaragoza en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

Mayo 18

4:00 p.m. - 5:00 p.m. (hora de Colombia)  

 

Algunos ejemplos de espacios topológicos tales que dim(X) = dim(K(X)) = 1 

Alfredo Zaragoza
Universidad Michoacana de San Nicolás de Hidalgo

Resumen. En general, si tenemos un espacio topológico X de dimensión uno, la dimensión de su hiperespacio de subconjuntos compactos K(X) con la topología de Vietoris no es finita. En esta plática presentamos varios ejemplos de espacios topológicos X de dimensión uno tales que la dimensión de su hiperespacio K(X) también es uno.

 

Zoom meeting information.

Meeting ID: 856 1882 0721

Passcode: 123456

https://cuaieed-unam.zoom.us/j/85618820721


Cross-Alps Logic Seminar (speaker: Jacques Duparc)

Cross-Alps Logic Seminar
On Friday 19.05.2023 at 16.00
Jacques Duparc (Université de Lausanne)
will give a talk on 
The Wadge order on the Cantor Space and on the Scott Domain

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Vincenzo

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Guozhen Shen from Wuhan University. This talk is going to take place this Friday,  May 19th,  from 4pm to 5pm(UTC+8, Beijing time). 

Title: A surjection from square onto power


Abstract: In 1892, Cantor proved that, for all sets $A$, there are no bijections between $A$ and the power set of $A$. Cantor's construction is so explicit that it can be carried out in ZF (the Zermelo--Fraenkel set theory without the axiom of choice). In 1906, by virtue of Zermelo's well-ordering theorem, Hessenberg proved the idempotency theorem, which states that there is a bijection between $A$ and the square of $A$ for all infinite sets $A$. (Another proof of the idempotency theorem was given by Zorn in 1944 using Zorn's lemma.) In 1924, Tarski proved that the idempotency theorem is in fact equivalent to the axiom of choice. On the other hand, in 1954, Specker proved in ZF a surprising generalization of Cantor's theorem, which states that, for all infinite sets $A$, there are no injections from the power set of $A$ into the square of $A$. It is then natural to ask whether it is provable in ZF that, for all infinite sets $A$, there are no surjections from the square of $A$ onto the power set of $A$. This question is known as the dual Specker problem and was proposed by Truss in 1973. In this talk, we give a negative answer to this question; that is, the existence of an infinite set $A$ such that the square of $A$ maps onto the power set of $A$ is consistent with ZF. This is joint work with Yinhe Peng and Liuzhen Wu.

__________________________________________________________________________________________________

Title The 29th Nankai Logic Colloquium --Guozhen Shen

Time 16:00pm, May. 19, 2023 (Beijing Time) 

Zoom Number 856 2849 0880

Passcode  073635

Link https://us02web.zoom.us/j/85628490880?pwd=dTBrV0NLc0l1bmFTY1RHR0d0TUNDZz09

_____________________________________________________________________


Best wishes,

Ming Xiao





This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 15, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 15, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Maciej Sendłak (Warsaw).
Title: Explanatory realism and counterfactuals

Abstract: In my talk, I want to propose a novel approach to the question of counterfactuals. This is grounded in two assumptions, imported from the philosophy of science. The first one has it that to explain a phenomenon is to show how it depends on something else. The second states that the correct explanation ought to be contrastive. This means that a good explanation justifies the occurrence of a phenomenon and – at the same time – excludes occurrence of some other states of affairs. I am going to argue that – together with the assumption that conditionals express a dependence relation between A and C – the above gives ground for analysis of counterfactuals. According to this proposal: “A>C” is true at the world of evaluation iff there is a relation of dependence that hold between referents of A and C, and the same relation of dependence holds in the world of evaluation.





- - - - Tuesday, May 16, 2023 - - - -



- - - - Wednesday, May 17, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Arthur Parzygnat, Nagoya University.

Date and Time:     Wednesday May 17, 2023, 7:00 - 8:30 PM. IN PERSON TALK.

Title:     Inferring the past and using category theory to define retrodiction.


Abstract: Classical retrodiction is the act of inferring the past based on knowledge of the present. The primary example is given by Bayes' rule P(y|x) P(x) = P(x|y) P(y), where we use prior information, conditional probabilities, and new evidence to update our belief of the state of some system. The question of how to extend this idea to quantum systems has been debated for many years. In this talk, I will lay down precise axioms for (classical and quantum) retrodiction using category theory. Among a variety of proposals for quantum retrodiction used in settings such as thermodynamics and the black hole information paradox, only one satisfies these categorical axioms. Towards the end of my talk, I will state what I believe is the main open question for retrodiction, formalized precisely for the first time. This work is based on the preprint https://arxiv.org/abs/2210.13531 and is joint work with Francesco Buscemi.





- - - - Thursday, May 18, 2023 - - - -



- - - - Friday, May 19, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 19, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.

Miha Habič, Bard College at Simon's Rock
Some old and new results on nonamalgamable forcing extensions

Fixing some countable transitive model  of set theory, we can consider its generic multiverse, the family of all models obtainable from  by taking any sequence of forcing extensions and ground models. There is an attractive similarity between the generic multiverse and the Turing degrees, but the multiverse has the drawback (or feature?) that it contains nonamalgamable models, that is, models with no common upper bound, as was observed by several people, going back to at least Mostowski. In joint work with Hamkins, Klausner, Verner, and Williams in 2019, we studied the order-theoretic properties of the generic multiverse and, among other results, gave a characterization of which partial orders embed nicely into the multiverse. I will present our results in the simplest case of Cohen forcing, as well as existing generalizations to wide forcing, and some new results on non-Cohen ccc forcings.




Next Week in Logic at CUNY:

- - - - Monday, May 22, 2023 - - - -



- - - - Tuesday, May 23, 2023 - - - -

MAMLS Spring Fling at Rutgers University
The MAMLS Spring Fling meeting will take place May 23-26 at Rutgers University, New Brunswick, New Jersey. More information about the meeting can be found on its website (https://sites.math.rutgers.edu/~fc327/MAMLS2023/index.html). Registration is free and everyone who plans to attend is encouraged to register for logistics purposes.


- - - - Wednesday, May 24, 2023 - - - -



- - - - Thursday, May 25, 2023 - - - -



- - - - Friday, May 26, 2023 - - - -





- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Applications of Set Theory, Lodz, Poland, September 4-8 2023

Conference
Dear All, We would like to inform you about the session "Applications of Set Theory" which will be held as a part of Spanish-Polish Mathematical Meeting in Lodz, Poland, 4-8 Sep 2023. The following people kindly agreed to speak at the session: * Alberto Salguero Alarcón (Badajoz) * David Aspero (Norwich) * Antonio Aviles (Murcia) * Taras Banakh (Lviv) * Piotr Koszmider (Warsaw) * Mikołaj Krupski (Murcia / Warsaw) * Jorge López Abad (Madrid) [tentative] * Witold Marciszewski (Warsaw) * Arturo Martínez-Celis (Wroclaw) * Robert Rałowski (Wroclaw) * Grigor Sargsyan (Gdansk) * Jacek Tryba (Gdansk) All the informations about the conference can be found at https://es-pl.math.uni.lodz.pl/ In particular, here https://es-pl.math.uni.lodz.pl/second.pdf you can find the second announcement. The conference fee is 300 EUR (up to June 30). It covers conference materials, lunches, coffee breaks, excursions, reception on September 4th and banquet on September 7th. Ph.D. students have reduced fee (150 EUR). There is a possibility to give a contributed talk at the session. If you have any questions please do not hesitate to contact us. Your sincerely, Antonio Aviles, Piotr Borodulin-Nadzieja, Szymon Glab, Jaroslaw Swaczyna
Link to more info

Nankai Logic Colloquium

Nankai Logic Colloquium

lHello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Maciej Malicki from Polish Academy of Sciences. This talk is going to take place this Friday,  May 12th,  from 4pm to 5pm(UTC+8, Beijing time). 

Title: Continuous logic and equivalence relations

Abstract: We will discuss two applications of infinitary continuous logic to Borel complexity of equivalence relations. We will characterize in model-theoretic terms essentially countable isomorphism relations on Borel classes of locally compact Polish metric structures. This gives a new proof of Kechris' theorem that orbit equivalence relations of actions of Polish locally compact groups are essentially countable. We will also show that isomorphism on such classes is always Borel reducible to graph isomorphism. This immediately answers a question of Gao and Kechris whether isometry of locally compact Polish metric spaces is reducible to graph isomorphism. The first result is joint work with Andreas Hallbäck and Todor Tsankov.


__________________________________________________________________________________________________

This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title : The 28th Nankai Logic Colloquium --Maciej Malicki 
Time :16:00pm, May. 12, 2023 (Beijing Time) 
Zoom Number : 880 6946 7024
Passcode : 142863
_____________________________________________________________________


Best wishes,

Ming Xiao




Charla de Jose Moncayo en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

Mayo 11

4:00 p.m. - 5:00 p.m. (hora de Colombia)  

 

Construcciones conjuntistas en modelos valuados y de Kripke

Jose R. Moncayo

Universidad Nacional de Colombia

 

Resumen. En esta charla se expondrán diferentes construcciones conjuntistas que buscan generalizar los modelos V y L en lógicas residuadas.

En primer lugar, usaremos la construcción de Scott y Solovay [1] (en donde se construye un modelo booleano de la teoría de conjuntos) para proponer dos definiciones de la noción de conjunto construible, tales que la primera terminará siendo isomorfa a V y la segunda a L.
En segundo lugar, mostraremos una generalización del trabajo de Fitting [2] sobre modelos de Kripke intuicionistas de la teoría de conjuntos. Para esto, se usarán los modelos de Kripke residuados de Ono y Komori [3, 4]. Propondremos una generalización de la jerarquía de von Neumann en el contexto de la lógica modal residuada y mostramos una traducción de fórmulas entre esta y una jerarquía de modelos Heyting valuados adecuados.

Referencias.
[1] Scott, D. & Solovay, R. (1967). Boolean-valued models for set theory.
[2] Fitting, M. (1969). Intuitionistic Logic, Model Theory and Forcing.
[3] Ono, H. & Komori, Y. (1985) Logics without the contraction rule.
[4] Ono, H. (1985) Semantical analysis of predicate logics without the contraction rule.

 

Zoom meeting information.

Meeting ID: 856 1882 0721

Passcode: 123456

https://cuaieed-unam.zoom.us/j/85618820721


This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 8, 2023 - - - -

Saul Kripke Memorial Conference
The Saul Kripke Center and CUNY Graduate Center
May 8-9, 2023, 9am-5pm, The Elebash Recital Hall, Graduate Center, CUNY

Registration for attending in person is not required, but attendees will have to comply with the Graduate Center’s Building Access PolicyAlthough the conference will be a mainly in person event, a livestream is also available; for this, please register.

Lectures:
Romina Birman, Paul Boghossian, Harry Field, Melvin
Fitting, Daniel Isaacson, Carl Posy, Robert Stalnaker

Reminiscences:
Eduardo Barrio, James Burgess, David Chalmers, Mircea
Dumitru, Margaret Gilbert, Anandi Hattiangadi, Antonella
Mallozzi, Oliver Marshall, Yiannis Moschovakis, Stephen
Neale, Gary Ostertag, David Papineau, Graham Priest, Scott
Soames, Larry Tribe, Timothy Williamson

With an introduction by:
Steve Everett, Provost and Senior Vice President, The CUNY Graduate Center




- - - - Tuesday, May 9, 2023 - - - -

Saul Kripke Memorial Conference
The Saul Kripke Center and CUNY Graduate Center
May 8-9, 2023, 9am-5pm, The Elebash Recital Hall, Graduate Center, CUNY

Registration for attending in person is not required, but attendees will have to comply with the Graduate Center’s Building Access PolicyAlthough the conference will be a mainly in person event, a livestream is also available; for this, please register.

Lectures:
Romina Birman, Paul Boghossian, Harry Field, Melvin
Fitting, Daniel Isaacson, Carl Posy, Robert Stalnaker

Reminiscences:
Eduardo Barrio, James Burgess, David Chalmers, Mircea
Dumitru, Margaret Gilbert, Anandi Hattiangadi, Antonella
Mallozzi, Oliver Marshall, Yiannis Moschovakis, Stephen
Neale, Gary Ostertag, David Papineau, Graham Priest, Scott
Soames, Larry Tribe, Timothy Williamson

With an introduction by:
Steve Everett, Provost and Senior Vice President, The CUNY Graduate Center






Models of Peano Arithmetic (MOPA)
Tuesday, May 9, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Mateusz Łełyk, University of Warsaw
Pathologies in Satisfaction Classes: part II

This is the second part of the talk given by Athar Abdul-Quader (Pathologically definable subsets of models of CT-), however we will make sure to make it self-contained.

The talk is centered around the following problem: when a subset of a countable and recursively saturated model M can be characterized as the set of the lengths of disjunctions on which a satisfaction class behaves correctly? More precisely: let DC(x) denote a sentence in a language of PA with a fresh binary predicate S which says 'For every disjunction d with at most x disjuncts and every assignment a, S(d,a) iff there is a disjunct d' in d such that S(d',a).' We say that X is a DC-set in (M,S) iff X is precisely the set of those numbers a such that (M,S) satisfies DC(a). We ask: given a countable and recursively saturated model M for which subsets X of M we can find a satisfaction class S such that X is a DC-set in (M,S)?

In the talk we study this problem for idempotent disjunctions, that is: disjunctions which repeat the same sentence. Let IDC(x) be DC(x) restricted to such 'idempotent' disjunctions of length x. The following is one of our core results:

Theorem: For an arbitrary countable and recursively saturated model M of PA the following conditions are equivalent:
(a) M is arithmetically saturated
(b) For every cut I in M there is a satisfaction class S such that I is an IDC-set in (M,S).

We study how this result generalizes to other propositional constructions in the place of disjunctions. The talk is based on a joint work with Athar Abdul-Quader presented in this paper from arxiv: arXiv:2303.18069v1 [math.LO] 31 Mar 2023.





- - - - Wednesday, May 10, 2023 - - - -

The Logic and Metaphysics Workshop special session
May 10th from 10:00-4:00 (NY time) 
CUNY Graduate Center, Kelly Skylight Room (in person)

10:00-11:30: Heinrich Wansing (Bochum)
Title: Quantifiers in connexive logic (in general and in particular)

Abstract: Connexive logic has room for two pairs of universal and particular quantifiers: one pair are standard quantifiers; the other pair are unorthodox, but we argue, are well-motivated in the context of connexive logic. Both non-standard quantifiers have been introduced previously, but in the context of connexive logic they have a natural semantic and proof-theoretic place, and plausible natural language readings. The result are logics which are negation inconsistent but non-trivial.
Note: This is joint work with Zach Weber (Otago).

12:30-2:00: Daniel Skurt (Bochum)
Title: RNmatrices for modal logics

Abstract: In this talk we will introduce a semantics for modal logics, based on so-called restricted Nmatrices (RNmatrices). These RNmatrices, previously used in the context of paraconsistent logics, prove to be a versatile tool for generating semantics for normal and non-normal systems of modal logics. Each of these semantics have sound and complete Hilbert-style calculi. The advantage of RNmatrices is that they provide a unifying framework for modal logics with or without first-order Kripke-frame conditions.
Note: This is joint work with Marcelo Coniglio (Campinas) and Pawel Pawlowski (Ghent).

2:30-4:00: Mark Colyvan (Sydney/LMU)
Title: Explanatory and non-explanatory proofs in mathematics

Abstract: In this paper I look at the contrast between explanatory and non-explanatory proofs in mathematics. This is done with the aim of shedding light on what distinguishes the explanatory proofs. I argue that there may be more than one notion of explanation in operation in mathematics: there does not seem to be a single account that ties together the different explanatory proofs found in mathematics. I then attempt to give a characterization of the different notions of explanation in play and how these sit with accounts of explanation found in philosophy of science.


- - - - Thursday, May 11, 2023 - - - -



- - - - Friday, May 12, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday May 12, 2:00pm-3:30pm, Room 6417

Brian Wynne, CUNY
Recent developments in the model theory of Abelian lattice-ordered groups

An Abelian lattice-ordered group (-group) is an Abelian group with a partial ordering, invariant under translations, that is a lattice ordering. A prototypical example of an -group is , the continuous real-valued functions on the topological space  with pointwise operations and ordering. Let  be the class of -groups, viewed as structures for the first-order language . After giving more background on -groups, I will survey what is known about the -groups existentially closed (e.c.) in , including some new examples I constructed using Fraïssé limits. Then I will discuss some recently published work of Scowcroft concerning the -groups e.c. in , the class of nonzero Archimedean -groups with distinguished strong order unit (viewed as structures for ). Building on Scowcroft's results, I will present new axioms for the -groups e.c. in  and show how they allow one to characterize those spaces  for which  is e.c. in .



Next Week in Logic at CUNY:

- - - - Monday, May 15, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 15, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Maciej Sendłak (Warsaw).
Title: Explanatory realism and counterfactuals

Abstract: In my talk, I want to propose a novel approach to the question of counterfactuals. This is grounded in two assumptions, imported from the philosophy of science. The first one has it that to explain a phenomenon is to show how it depends on something else. The second states that the correct explanation ought to be contrastive. This means that a good explanation justifies the occurrence of a phenomenon and – at the same time – excludes occurrence of some other states of affairs. I am going to argue that – together with the assumption that conditionals express a dependence relation between A and C – the above gives ground for analysis of counterfactuals. According to this proposal: “A>C” is true at the world of evaluation iff there is a relation of dependence that hold between referents of A and C, and the same relation of dependence holds in the world of evaluation.





- - - - Tuesday, May 16, 2023 - - - -



- - - - Wednesday, May 17, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Arthur Parzygnat, Nagoya University.

Date and Time:     Wednesday May 17, 2023, 7:00 - 8:30 PM. IN PERSON TALK.

Title:     Inferring the past and using category theory to define retrodiction.


Abstract: Classical retrodiction is the act of inferring the past based on knowledge of the present. The primary example is given by Bayes' rule P(y|x) P(x) = P(x|y) P(y), where we use prior information, conditional probabilities, and new evidence to update our belief of the state of some system. The question of how to extend this idea to quantum systems has been debated for many years. In this talk, I will lay down precise axioms for (classical and quantum) retrodiction using category theory. Among a variety of proposals for quantum retrodiction used in settings such as thermodynamics and the black hole information paradox, only one satisfies these categorical axioms. Towards the end of my talk, I will state what I believe is the main open question for retrodiction, formalized precisely for the first time. This work is based on the preprint https://arxiv.org/abs/2210.13531 and is joint work with Francesco Buscemi.





- - - - Thursday, May 18, 2023 - - - -



- - - - Friday, May 19, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 19, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.

Miha Habič, Bard College at Simon's Rock
Some old and new results on nonamalgamable forcing extensions

Fixing some countable transitive model  of set theory, we can consider its generic multiverse, the family of all models obtainable from  by taking any sequence of forcing extensions and ground models. There is an attractive similarity between the generic multiverse and the Turing degrees, but the multiverse has the drawback (or feature?) that it contains nonamalgamable models, that is, models with no common upper bound, as was observed by several people, going back to at least Mostowski. In joint work with Hamkins, Klausner, Verner, and Williams in 2019, we studied the order-theoretic properties of the generic multiverse and, among other results, gave a characterization of which partial orders embed nicely into the multiverse. I will present our results in the simplest case of Cohen forcing, as well as existing generalizations to wide forcing, and some new results on non-Cohen ccc forcings.






- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

(KGRC) Set Theory Seminar talk on TUESDAY, May 9

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Thilo Weinert (host: Vera Fischer) visits the KGRC until June 30 and gives a talk, see below. Sergei Starchenko (host: Matthias Aschenbrenner) visits the KGRC from May 13 to May 27 and gives a talk, details to be announced at a later time. Fabian Kaak (host: Vera Fischer) visits the KGRC from May 23 to May 26 and gives a short talk, details to be announced at a later time. Ido Feldman (host: Miguel Moreno) visits the KGRC from June 11 to June 17 and gives a talk, details to be announced at a later time. Jaroslav Šupina (host: Vera Fischer) visits the KGRC from June 18 to June 24 and gives a talk, details to be announced at a later time. Nadiya Kolos (host: Miguel Moreno) visits the KGRC from June 19 to June 23 and gives a talk, details to be announced at a later time. * * * Set Theory Seminar Kurt Gödel Research Center TUESDAY, May 9 (Please note the unusual day and the time!) "On Unsound Linear Orderings" Thilo Weinert In the Eighties Adrian Mathias introduced the notion of soundness of an ordinal. An ordinal is sound if for any countable partition P of it only countably many ordinals are order-types of unions of subpartitionts of P. Mathias showed that the least unsound ordinal $\zeta$ is $\omega_1^{\omega + 2}$ if $\aleph_1$ can be embedded into the continuum but if $\aleph_1$ is regular yet cannot be embedded into the continuum, $\zeta \geqslant \omega_1^{\omega 2 + 1}$. I am going to discuss his findings and consider the notion for the more general class of linear orderings building on work by him, MacPherson, and Schmerl. I am also going to mention some open problems. This is joint ongoing work with Garrett Ervin and Jonathan Schilhan. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 10th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There will be no seminars during a couple of weeks after next the next one. The seminar will more likely meet again on Wednesday June 21st. Program: Tomas Jakl -- Game comonads and the composition methods Composition methods are a key technique in finite model theory, which enables modular reasoning about complex structures. Examples of such theorems are Mostowski theorem and Feferman-Vaught theorems, which express that logical equivalence of structures is congruent with respect to the operations of disjoint union and products of structures. Typical applications of composition methods in finite model theory are Courcelle's algorithmic meta theorems. In this talk I will give a brief overview of game comonads, a new tool from category theory in finite model theory, and discuss how they allow us to prove very general Feferman-Vaught-Mostowski theorems. Comonads are the formally dual notion to monads, where the latter can be used to describe algebraic systems over arbitrary domains. For example, topological groups can be viewed as algebras over topological spaces. Game comonads are an approach to creating comonads by semantically encoding a game-theoretic description of logical equivalence. Our approach allows us to make use of a categorical description of tensor products and bilinear maps of vector spaces. Best, David

Logic Seminar 10 May 2023 17:00 hrs at NUS by Jan Baars

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 10 May 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Speaker: Jan Baars Title: Generalisations of a result by Gulko on spaces of continuous functions URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Please find the abstract attached.

Cross-Alps Logic Seminar (speaker: Dima Sinapova)

Cross-Alps Logic Seminar
On Friday 05.05.2023 at 16.00
Dima Sinapova (Rutgers University)
will give a talk on 
Mutual stationarity and the failure of SCH

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Vincenzo

Charla de Joel Aguilar en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

Mayo 4

4:00 p.m. - 5:00 p.m. (hora de Colombia)  

 

Subespacios "grandes" de C_p(X) y sus invariantes cardinales

Joel Aguilar

Universidad Michoacana de San Nicolás de Hidalgo

 

Resumen. Sea C_p(X) el espacio de funciones continuas de X en R con la topología de la convergencia puntual (para garantizar que C_p(X) sea no trivial en esta plática asumiremos que todos los espacios estudiados son de Tychonoff). Una técnica común para obtener información de un espacio X es estudiar las propiedades de sus subespacios "suficientemente grandes"; por ejemplo, un espacio con un subespacio denso y psuedocompacto tiene que ser pseudocompacto; un espacio no puede ser de Lindelöf si tiene un subespacio no-numerable, discreto y cerrado; etc. En la plática nos enfocaremos en los subespacios de C_p(X) que también son densos en la topología uniforme y discutiremos cómo se relacionan las propiedades de estos subespacios con las de C_p(X).

 

Zoom meeting information.

Meeting ID: 856 1882 0721

Passcode: 123456

https://cuaieed-unam.zoom.us/j/85618820721


Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

Sorry for the interrupting again. I would like to apologize(again) for a mistake in the previous announcement. There was a serious mistake in the time mentioned. The correct time of the Nankai Logic Colloquium this week is in the afternoon, 4pm to 5pm (instead of morning mentioned in the last email), Friday Beijing time. I am very very sorry for the confuse it may cause.

The following is a corrected version of the announcement for this week:

_____________________________________________________

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Ilijas Farah from York University. This talk is going to take place this Friday,  May 5th,  from 4pm to 5pm(UTC+8, Beijing time). 

Title:  Corona rigidity


Abstract. Reduced powers associated with the Frech\'et filter are well-known to be countably saturated (that is, $\aleph_1$-saturated). Because of this the Continuum Hypothesis implies that the reduced power of every countable structure has $2^{2^{\aleph_0}}$ automorphisms, and that for such reduced powers elementary equivalence is a sufficient condition for isomorphism. On the other hand, forcing axioms imply that some reduced powers (e.g., those of finite Boolean algebras) have only trivial automorphisms while some other reduced powers are saturated and they $2^{2^{\aleph_0}}$ automorphisms, provably in ZFC (e.g., those of the 2-element cyclic group).

This begs two questions: Which structures have saturated reduced powers, provably in ZFC? For which structures forcing axioms imply the `corona rigidity', that their reduced powers have only trivial automorphisms?
I will give a complete answer to the first question and a partial (rather surprising) answer to the second.

__________________________________________________________________________________________________

This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title : The 27th Nankai Logic Colloquium --Ilijas Farah
Time :16:00pm, May. 05, 2023 (Beijing Time) 
Zoom Number : 827 3827 3373
Passcode : 821730
Link :https://us02web.zoom.us/j/82738273373?pwd=ZnFYbEFUSWErcDVROFUrQnZ1WGNxZz09
_____________________________________________________________________


Best wishes,

Ming Xiao






Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 3rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There is no fixed program yet. We will meet and see what are we interested in hearing/working on. Walk-in speakers are welcome. Best, David

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

I would like to apologize for a mistake in the previous announcement. There was a typo in the time mentioned. The correct time is 9am to 10am (instead of 10pm). I am very sorry for the confuse it may cause.

The following is a corrected version of the previous email:

_____________________________________________________

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Ilijas Farah from York University. This talk is going to take place this Friday,  May 5th,  from 9am to 10am(UTC+8, Beijing time). 

Title:  Corona rigidity


Abstract. Reduced powers associated with the Frech\'et filter are well-known to be countably saturated (that is, $\aleph_1$-saturated). Because of this the Continuum Hypothesis implies that the reduced power of every countable structure has $2^{2^{\aleph_0}}$ automorphisms, and that for such reduced powers elementary equivalence is a sufficient condition for isomorphism. On the other hand, forcing axioms imply that some reduced powers (e.g., those of finite Boolean algebras) have only trivial automorphisms while some other reduced powers are saturated and they $2^{2^{\aleph_0}}$ automorphisms, provably in ZFC (e.g., those of the 2-element cyclic group).

This begs two questions: Which structures have saturated reduced powers, provably in ZFC? For which structures forcing axioms imply the `corona rigidity', that their reduced powers have only trivial automorphisms?
I will give a complete answer to the first question and a partial (rather surprising) answer to the second.

__________________________________________________________________________________________________

This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title : The 27th Nankai Logic Colloquium --Ilijas Farah
Time :9:00am, May. 05, 2023 (Beijing Time) 
Zoom Number : 827 3827 3373
Passcode : 821730
Link :https://us02web.zoom.us/j/82738273373?pwd=ZnFYbEFUSWErcDVROFUrQnZ1WGNxZz09
_____________________________________________________________________


Best wishes,

Ming Xiao





Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Ilijas Farah from York University. This talk is going to take place this Friday,  May 5th,  from 9am to 10pm(UTC+8, Beijing time). 

Title:  Corona rigidity


Abstract. Reduced powers associated with the Frech\'et filter are well-known to be countably saturated (that is, $\aleph_1$-saturated). Because of this the Continuum Hypothesis implies that the reduced power of every countable structure has $2^{2^{\aleph_0}}$ automorphisms, and that for such reduced powers elementary equivalence is a sufficient condition for isomorphism. On the other hand, forcing axioms imply that some reduced powers (e.g., those of finite Boolean algebras) have only trivial automorphisms while some other reduced powers are saturated and they $2^{2^{\aleph_0}}$ automorphisms, provably in ZFC (e.g., those of the 2-element cyclic group).

This begs two questions: Which structures have saturated reduced powers, provably in ZFC? For which structures forcing axioms imply the `corona rigidity', that their reduced powers have only trivial automorphisms?
I will give a complete answer to the first question and a partial (rather surprising) answer to the second.

__________________________________________________________________________________________________

This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title : The 27th Nankai Logic Colloquium --Ilijas Farah
Time :9:00am, May. 05, 2023 (Beijing Time) 
Zoom Number : 827 3827 3373
Passcode : 821730
Link :https://us02web.zoom.us/j/82738273373?pwd=ZnFYbEFUSWErcDVROFUrQnZ1WGNxZz09
_____________________________________________________________________


Best wishes,

Ming Xiao




This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 1, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 1, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Samara Burns (Columbia).
Title: Understanding (and) surveyability

Abstract: In this talk I will discuss the notion of surveyable proof. Discussions of surveyability emerge periodically in recent philosophical literature, but the notion of surveyable proof can be traced back to Descartes. Despite this long history, there is still disagreement about what features a proof must have in order to count as surveyable. This disagreement arises, in part, because there is still significant vagueness regarding the problem that unsurveyability poses for the epistemology of mathematics. I identify three features of justification in mathematics that could be at issue in the surveyability debate: a priority, internalism, and certainty. Each of these features is prima facie troubled by unsurveyable proof. In each case, however, I’ll argue that unsurveyable proof does not pose any real issue. I will suggest that the surveyability debate should not be framed in terms of justification at all, and that the problem is really about mathematical understanding.



- - - - Tuesday, May 2, 2023 - - - -



- - - - Wednesday, May 3, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Gemma De las Cuevas, University of Innsbruck.

Date and Time:     Wednesday May 3, 2023, 7:00 - 8:30 PM. ZOOM TALK.

Title:     A framework for universality across disciplines.


Abstract: What is the scope of universality across disciplines? And what is its relation to undecidability? To address these questions, we build a categorical framework for universality. Its instances include Turing machines, spin models, and others. We introduce a hierarchy of universality and argue that it distinguishes universal Turing machines as a non-trivial form of universality. We also outline the relation to undecidability by drawing a connection to Lawvere’s Fixed Point Theorem. Joint work with Sebastian Stengele, Tobias Reinhart and Tomas Gonda.





- - - - Thursday, May 4, 2023 - - - -



- - - - Friday, May 5, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
NOTE UPDATED TIME: Friday, May 5, 10:00am NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Joel David Hamkins, Notre Dame University

Realizing Frege's Basic Law V, provably in ZFC

The standard set-theoretic distinction between sets and classes instantiates in important respects the Fregean distinction between objects and concepts, for in set theory we commonly take the universe of sets as a realm of objects to be considered under the guise of diverse concepts, the definable classes, each serving as a predicate on that domain of individuals. Although it is commonly held that in a very general manner, there can be no association of classes with objects in a way that fulfills Frege's Basic Law V, nevertheless, in the ZF framework, it turns out that we can provide a completely deflationary account of this and other Fregean abstraction principles. Namely, there is a mapping of classes to objects, definable in set theory in senses I shall explain (hence deflationary), associating every first-order parametrically definable class  with a set object , in such a way that Basic Law V is fulfilled:
Russell's elementary refutation of the general comprehension axiom, therefore, is improperly described as a refutation of Basic Law V itself, but rather refutes Basic Law V only when augmented with powerful class comprehension principles going strictly beyond ZF. The main result leads also to a proof of Tarski's theorem on the nondefinability of truth as a corollary to Russell's argument. A central goal of the project is to highlight the issue of definability and deflationism for the extension assignment problem at the core of Fregean abstraction.



Logic Workshop
CUNY Graduate Center
Friday May 5, 2:00pm-3:30pm, Room 6417
Karen Lange, Wellesley College

Classification via effective lists

'Classifying' a natural collection of structures is a common goal in mathematics. Providing a classification can mean different things, e.g., identifying a set of invariants that settle the isomorphism problem or creating a list of all structures of a given kind without repetition of isomorphism type. Here we discuss recent work on classifications of the latter kind from the perspective of computable structure theory. We’ll consider natural classes of computable structures such as vector spaces, equivalence relations, algebraic fields, and trees to better understand the nuances of classification via effective lists and its relationship to other forms of classification in this setting.



Next Week in Logic at CUNY:

- - - - Monday, May 8, 2023 - - - -

Saul Kripke Memorial Conference
The Saul Kripke Center and CUNY Graduate Center
May 8-9, 2023, 9am-5pm, The Elebash Recital Hall, Graduate Center, CUNY

Registration for attending in person is not required, but attendees will have to comply with the Graduate Center’s Building Access PolicyAlthough the conference will be a mainly in person event, a livestream is also available; for this, please register.

Lectures:
Romina Birman, Paul Boghossian, Harry Field, Melvin
Fitting, Daniel Isaacson, Carl Posy, Robert Stalnaker

Reminiscences:
Eduardo Barrio, James Burgess, David Chalmers, Mircea
Dumitru, Margaret Gilbert, Anandi Hattiangadi, Antonella
Mallozzi, Oliver Marshall, Yiannis Moschovakis, Stephen
Neale, Gary Ostertag, David Papineau, Graham Priest, Scott
Soames, Larry Tribe, Timothy Williamson

With an introduction by:
Steve Everett, Provost and Senior Vice President, The CUNY Graduate Center




- - - - Tuesday, May 9, 2023 - - - -

Saul Kripke Memorial Conference
The Saul Kripke Center and CUNY Graduate Center
May 8-9, 2023, 9am-5pm, The Elebash Recital Hall, Graduate Center, CUNY

Registration for attending in person is not required, but attendees will have to comply with the Graduate Center’s Building Access PolicyAlthough the conference will be a mainly in person event, a livestream is also available; for this, please register.

Lectures:
Romina Birman, Paul Boghossian, Harry Field, Melvin
Fitting, Daniel Isaacson, Carl Posy, Robert Stalnaker

Reminiscences:
Eduardo Barrio, James Burgess, David Chalmers, Mircea
Dumitru, Margaret Gilbert, Anandi Hattiangadi, Antonella
Mallozzi, Oliver Marshall, Yiannis Moschovakis, Stephen
Neale, Gary Ostertag, David Papineau, Graham Priest, Scott
Soames, Larry Tribe, Timothy Williamson

With an introduction by:
Steve Everett, Provost and Senior Vice President, The CUNY Graduate Center






Models of Peano Arithmetic (MOPA)
Tuesday, May 9, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Mateusz Łełyk, University of Warsaw
Pathologies in Satisfaction Classes: part II

This is the second part of the talk given by Athar Abdul-Quader (Pathologically definable subsets of models of CT-), however we will make sure to make it self-contained.

The talk is centered around the following problem: when a subset of a countable and recursively saturated model M can be characterized as the set of the lengths of disjunctions on which a satisfaction class behaves correctly? More precisely: let DC(x) denote a sentence in a language of PA with a fresh binary predicate S which says 'For every disjunction d with at most x disjuncts and every assignment a, S(d,a) iff there is a disjunct d' in d such that S(d',a).' We say that X is a DC-set in (M,S) iff X is precisely the set of those numbers a such that (M,S) satisfies DC(a). We ask: given a countable and recursively saturated model M for which subsets X of M we can find a satisfaction class S such that X is a DC-set in (M,S)?

In the talk we study this problem for idempotent disjunctions, that is: disjunctions which repeat the same sentence. Let IDC(x) be DC(x) restricted to such 'idempotent' disjunctions of length x. The following is one of our core results:

Theorem: For an arbitrary countable and recursively saturated model M of PA the following conditions are equivalent:
(a) M is arithmetically saturated
(b) For every cut I in M there is a satisfaction class S such that I is an IDC-set in (M,S).

We study how this result generalizes to other propositional constructions in the place of disjunctions. The talk is based on a joint work with Athar Abdul-Quader presented in this paper from arxiv: arXiv:2303.18069v1 [math.LO] 31 Mar 2023.





- - - - Wednesday, May 10, 2023 - - - -

The Logic and Metaphysics Workshop special session
May 10th from 10:00-4:00 (NY time) 
CUNY Graduate Center, Kelly Skylight Room (in person)

10:00-11:30: Heinrich Wansing (Bochum)
Title: Quantifiers in connexive logic (in general and in particular)

Abstract: Connexive logic has room for two pairs of universal and particular quantifiers: one pair are standard quantifiers; the other pair are unorthodox, but we argue, are well-motivated in the context of connexive logic. Both non-standard quantifiers have been introduced previously, but in the context of connexive logic they have a natural semantic and proof-theoretic place, and plausible natural language readings. The result are logics which are negation inconsistent but non-trivial.
Note: This is joint work with Zach Weber (Otago).

12:30-2:00: Daniel Skurt (Bochum)
Title: RNmatrices for modal logics

Abstract: In this talk we will introduce a semantics for modal logics, based on so-called restricted Nmatrices (RNmatrices). These RNmatrices, previously used in the context of paraconsistent logics, prove to be a versatile tool for generating semantics for normal and non-normal systems of modal logics. Each of these semantics have sound and complete Hilbert-style calculi. The advantage of RNmatrices is that they provide a unifying framework for modal logics with or without first-order Kripke-frame conditions.
Note: This is joint work with Marcelo Coniglio (Campinas) and Pawel Pawlowski (Ghent).

2:30-4:00: Mark Colyvan (Sydney/LMU)
Title: Explanatory and non-explanatory proofs in mathematics

Abstract: In this paper I look at the contrast between explanatory and non-explanatory proofs in mathematics. This is done with the aim of shedding light on what distinguishes the explanatory proofs. I argue that there may be more than one notion of explanation in operation in mathematics: there does not seem to be a single account that ties together the different explanatory proofs found in mathematics. I then attempt to give a characterization of the different notions of explanation in play and how these sit with accounts of explanation found in philosophy of science.


- - - - Thursday, May 11, 2023 - - - -



- - - - Friday, May 12, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday May 12, 2:00pm-3:30pm, Room 6417

Brian Wynne, CUNY
Recent developments in the model theory of Abelian lattice-ordered groups

An Abelian lattice-ordered group (-group) is an Abelian group with a partial ordering, invariant under translations, that is a lattice ordering. A prototypical example of an -group is , the continuous real-valued functions on the topological space  with pointwise operations and ordering. Let  be the class of -groups, viewed as structures for the first-order language . After giving more background on -groups, I will survey what is known about the -groups existentially closed (e.c.) in , including some new examples I constructed using Fraïssé limits. Then I will discuss some recently published work of Scowcroft concerning the -groups e.c. in , the class of nonzero Archimedean -groups with distinguished strong order unit (viewed as structures for ). Building on Scowcroft's results, I will present new axioms for the -groups e.c. in  and show how they allow one to characterize those spaces  for which  is e.c. in .



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
Saul Kripke Memorial Conference
May 8-9, 2023
The Saul Kripke Center and CUNY Graduate Center

The Saul Kripke Center will host a memorial conference honoring Saul Kripke (1940-2022) at The CUNY Graduate Center on May 8th and 9th, 2023. The conference program is available here. Registration for attending in person is not required, but attendees will have to comply with the Graduate Center’s Building Access Policy. Although the conference will be a mainly in person event, a livestream is also available; for this, please register.



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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(KGRC) two talks on Thursday, May 4

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Heike Mildenberger (host: Vera Fischer) visits the KGRC from May 3 to May 6 and gives a talk on May 4, see below. Fabian Kaak (host: Vera Fischer) visits the KGRC from May 23 to May 26 and gives a short talk, details to be announced at a later time. Ido Feldman (host: Miguel Moreno) visits the KGRC from June 11 to June 17 and gives a talk, details to be announced at a later time. Jaroslav Šupina (host: Vera Fischer) visits the KGRC from June 18 to June 24 and gives a talk, details to be announced at a later time. Nadiya Kolos (host: Miguel Moreno) visits the KGRC from June 19 to June 23 and gives a talk, details to be announced at a later time. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, May 4 "Coding with localization forcing and generalized descriptive set theory" Lyubomyr Zdomskyy (TU Wien) There are many known ways how to make various objects definable by designing a suitable description for them with the help of forcing. One of such methods is based on so-called localization invented by R. David and further developed by S. Friedman, V. Fischer, D. Schrittesser, and many others. We shall discuss the application of this method to the study of Borel* subsets of 2^kappa for a successor cardinal kappa. Joint work with Miguel Moreno. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, May 4 "Destroying Guessing Principles" Heike Mildenberger (University of Freiburg, DE) An Ostaszewski club sequence is a weakening of Jensen's diamond. In contrast to the diamond, the club does not imply the continuum hypothesis. Numerous questions about the club stay open, and we know only few models in which there is just a club sequence but no diamond sequence. In recent joint work with Shelah we found that a winning strategy for the completeness player in a bounding game on a forcing order does not suffice to establish the club in the extension. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at.

Charla de Diana Montoya en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

Abril 27

4:00 p.m. - 5:00 p.m. (hora de Colombia)  

 

Cardinales característicos en el caso no enumerable
Diana C. Montoya

Universidad Técnica de Viena

 

Resumen. En la primera parte de esta charla, presentaré la motivación y algunos resultados generales de la teoría de cardinales característicos en los espacios de Baire generalizados $\kappa^\kappa$; asimismo, presentaré un resumen del estado del arte actual de este tema. En la segunda parte, me enfocaré en el concepto de independencia maximal en estos espacios para el caso en el cual $\kappa$ es un cardinal regular (medible), y también en el caso en el que $\kappa$ es singular. Al final, mencionaré algunas preguntas abiertas y futuras líneas de investigación. 


Zoom meeting information.
Meeting ID: 856 1882 0721
Passcode: 123456

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Ronnie Chen from the University of Michigan. This talk is going to take place this Friday,  Apr 28th,  from 9am to 10pm(UTC+8, Beijing time). 

Title: Topology versus Borel structure for actions

Abstract: A "nice" (e.g., Polish) topology contains a lot more structure than its induced Borel $\sigma$-algebra. On the other hand, Pettis's theorem says that a Polish group topology is completely determined by its induced Borel group structure. The Becker--Kechris theorem interpolates between these two extreme behaviors in the context of group actions, by characterizing the compatible topologies on a Borel $G$-space. We give a new proof of a strengthened version of the core ingredient in the Becker--Kechris theorem, that clarifies its connection to several other results in the theory of Polish group actions, as well as generalizing cleanly to other contexts such as non-Hausdorff spaces, Borel first-order $G$-structures, and groupoid actions.

__________________________________________________________________________________________________

This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title : The 26th Nankai Logic Colloquium --Ronnie Chen

Time :9:00am, Apr. 28, 2023 (Beijing Time) 

Zoom Number : 840 0998 2925

Passcode : 553830

_____________________________________________________________________


Best wishes,

Ming Xiao




This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 24, 2023 - - - -

Rutgers Logic Seminar 
Monday, April 24, 2pm, Rutgers University, Hill 005
Aristotelis Panagiotopoulos, CMU


Logic and Metaphysics Workshop
Date: Monday, April 24, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Andrea Iacona (Turin).
Title: Inferentialism and connexivity

Abstract: In my talk I will investigate the relationships between two claims about conditionals that by and large are discussed separately. One is the claim that a conditional holds when its consequent can be inferred from its antecedent, or when the latter provides a reason for accepting the former. The other is the claim that conditionals intuitively obey some characteristic connexive principles, such as Aristotle’s Thesis and Boethius Thesis. Following a line of thought that goes back to Chrysippus, I will suggest that these two claims may coherently be understood as distinct manifestations of a single basic idea, namely, that a conditional holds when its antecedent is incompatible with the negation of its consequent. The account of conditionals that I will outline is based precisely on this idea.



- - - - Tuesday, Apr 25, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 25, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Mateusz Łełyk University of Warsaw

Pathologies in Satisfaction Classes

This is the second part of the talk given by Athar Abdul-Quader (Pathologically definable subsets of models of CT-), however we will make sure to make it self-contained.

The talk is centered around the following problem: when a subset of a countable and recursively saturated model M can be characterized as the set of the lengths of disjunctions on which a satisfaction class behaves correctly? More precisely: let DC(x) denote a sentence in a language of PA with a fresh binary predicate S which says 'For every disjunction d with at most x disjuncts and every assignment a, S(d,a) iff there is a disjunct d' in d such that S(d',a).' We say that X is a DC-set in (M,S) iff X is precisely the set of those numbers a such that (M,S) satisfies DC(a). We ask: given a countable and recursively saturated model M for which subsets X of M we can find a satisfaction class S such that X is a DC-set in (M,S)?

In the talk we study this problem for idempotent disjunctions, that is: disjunctions which repeat the same sentence. Let IDC(x) be DC(x) restricted to such 'idempotent' disjunctions of length x. The following is one of our core results:

Theorem: For an arbitrary countable and recursively saturated model M of PA the following conditions are equivalent:
(a) M is arithmetically saturated
(b) For every cut I in M there is a satisfaction class S such that I is an IDC-set in (M,S).

We study how this result generalizes to other propositional constructions in the place of disjunctions. The talk is based on a joint work with Athar Abdul-Quader presented in this paper from arxiv: arXiv:2303.18069v1 [math.LO] 31 Mar 2023.




- - - - Wednesday, Apr 26, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Dusko Pavlovic, University of Hawai‘i at Mānoa.

Date and Time:     Wednesday April 26, 2023, 7:00 - 8:30 PM. ZOOM TALK.

Title:     Program-closed categories.


Abstract: > Let CC be a symmetric monoidal category with a comonoid on every object. Let CC* be the cartesian subcategory with the same objects and just the comonoid homomorphisms. A *programming language* is a well-ordered object P with a *program closure*: a family of X-natural surjections
CC(XA,B) <<--run_X-- CC*(X,P)
one for every pair A,B. In this talk, I will sketch a proof that program closure is a property: Any two programming languages are isomorphic along run-preserving morphisms. The result counters Kleene's interpretation of the Church-Turing Thesis, which has been formalized categorically as the suggestion that computability is a structure, like a group presentation, and not a property, like completeness. We prove that it is like completeness. The draft of a book on categorical computability is available from the web site dusko.org.




- - - - Thursday, Apr 27, 2023 - - - -



- - - - Friday, Apr 28, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 28, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Will Boney Texas State University



Next Week in Logic at CUNY:

- - - - Monday, May 1, 2023 - - - -



- - - - Tuesday, May 2, 2023 - - - -



- - - - Wednesday, May 3, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Gemma De las Cuevas, University of Innsbruck.

Date and Time:     Wednesday May 3, 2023, 7:00 - 8:30 PM. ZOOM TALK.

Title:     A framework for universality across disciplines.


Abstract: What is the scope of universality across disciplines? And what is its relation to undecidability? To address these questions, we build a categorical framework for universality. Its instances include Turing machines, spin models, and others. We introduce a hierarchy of universality and argue that it distinguishes universal Turing machines as a non-trivial form of universality. We also outline the relation to undecidability by drawing a connection to Lawvere’s Fixed Point Theorem. Joint work with Sebastian Stengele, Tobias Reinhart and Tomas Gonda.





- - - - Thursday, May 4, 2023 - - - -



- - - - Friday, May 5, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 5, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Joel David Hamkins Notre Dame University



Logic Workshop
CUNY Graduate Center
Friday May 5, 2:00pm-3:30pm, Room 6417
Karen Lange, Wellesley College

Classification via effective lists

'Classifying' a natural collection of structures is a common goal in mathematics. Providing a classification can mean different things, e.g., identifying a set of invariants that settle the isomorphism problem or creating a list of all structures of a given kind without repetition of isomorphism type. Here we discuss recent work on classifications of the latter kind from the perspective of computable structure theory. We’ll consider natural classes of computable structures such as vector spaces, equivalence relations, algebraic fields, and trees to better understand the nuances of classification via effective lists and its relationship to other forms of classification in this setting.



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT
Saul Kripke Memorial Conference
May 8-9, 2023
The Saul Kripke Center and CUNY Graduate Center

The Saul Kripke Center will host a memorial conference honoring Saul Kripke (1940-2022) at The CUNY Graduate Center on May 8th and 9th, 2023. The conference program is available here. Registration for attending in person is not required, but attendees will have to comply with the Graduate Center’s Building Access Policy. Although the conference will be a mainly in person event, a livestream is also available; for this, please register.



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

(KGRC) talks in the Set Theory Seminar on April 25 and April 27

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Sergei Starchenko (host: Matthias Aschenbrenner) visits the KGRC from April 16 to April 30 and gives a talk, details to be announced at a later time. Tomasz Żuchowski (host: Damian Sobota) visits the KGRC from April 24 to April 30 and gives a talk, see below. Heike Mildenberger (host: Vera Fischer) visits the KGRC from May 3 to May 6 and gives a talk on May 4, details to be announced at a later time. Fabian Kaak (host: Vera Fischer) visits the KGRC from May 23 to May 26 and gives a short talk, details to be announced at a later time. Jaroslav Šupina (host: Vera Fischer) visits the KGRC from June 18 to June 24 and gives a talk, details to be announced at a later time. Nadiya Kolos (host: Miguel Moreno) visits the KGRC from June 19 to June 23 and gives a talk, details to be announced at a later time. * * * Set Theory Seminar Kurt Gödel Research Center Tuesday, April 25 "Nonseparable growth of $\omega$ supporting a strictly positive measure" Tomasz Żuchowski (University of Wrocław, PL) During the talk I will present a construction in ZFC of a compactification of $\omega$ such that its remainder is not separable and carries a strictly positive measure, i.e. measure positive on nonempty open subsets. The measure is defined using the asymptotic density of subsets of $\omega$. The remainder is a Stone space of some Boolean subalgebra of Borel subsets of the Cantor space containing all clopen sets, constructed with an aid of an uncountable almost disjoint family of subsets of $\omega$. This is a joint work with Piotr Borodulin-Nadzieja. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Set Theory Seminar Kurt Gödel Research Center Thursday, April 27 "Cardinalities of sets of reals satisfying combinatorial covering properties" Lyubomyr Zdomskyy (TU Wien) We shall discuss which cardinalities sets of reals satisfying Menger and Hurewicz covering properties may have in some standard models of ZFC. Most of the results may be thought of as consistent instances of the Perfect Set Property, since they state that in some models, a set of reals satisfying certain covering properties either contains a copy of the Cantor set, or has small size. In particular, we plan to outline the proof of the fact that in the Sacks model every Menger totally imperfect set of reals has size at most w_1. This is a joint work with V. Haberl and P. Szewczak. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk to vera.fischer@univie.ac.at.

Wednesday seminar -- joint seminar of the MLTCS department

Prague Set Theory Seminar
Dear all, The seminar next week will be held as a joint seminar of the MLTCS department. This means we expect a slightly wider audience and the plan is to go for a lunch after the seminar. Please do let me know if you intend to come so that we can make estimates for the table reservation. ***ROOM CHANGE*** The seminar will meet on Wednesday April 26th at 11:00 in the Institute of Mathematics CAS, blue lecture hall, ground floor, rear building, Zitna 25. Program: David Uhrik -- Colorings of Infinite Graphs We will give an overview of new results on uncountable graphs obtained in my phd thesis. Topics will range from Ramsey theory, the chromatic number to the uncountable Hadwiger conjecture. We studied various graph constructions in Cohen extensions. We showed that adding aleph-two Cohen reals forces a weak bipartite-type partition relation on aleph-two. From a single Cohen real we constructed a triangle free Hajnal--Máté graph, answering a question of Dániel Soukup. Using the same method a new construction of a T-Hajnal--Máté graph was provided in ZFC. We introduced so-called delta-Hajnal--Máté graphs and showed that they do not exist under Martin's axiom. Lastly in connection to the uncountable Hadwiger conjecture we proved that the least size of a counterexample to the uncountable Hadwiger conjecture is equal to the special tree number. Best, David

Charla de Andrés Uribe en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

Abril 20

4:00 p.m. - 5:00 p.m. (hora de Colombia)  

 

FAM-ligadura: hacia una teoría general de forcing iterado usando medidas finitamente aditivas.
Andrés F. Uribe

Universidad Nacional de Colombia

 

Resumen. En el año 2000, Shelah logró demostrar que, consistentemente, el número de cubrimiento del ideal de los subconjuntos nulos de los números reales puede tener cofinalidad contable. Para ello, usando random forcing, construyó una iteración de soporte finito con medidas finitamente aditivas. En esta charla se va a presentar la definición de una nueva noción de ligadura, llamada FAM-ligadura, que permite generalizar la iteración que Shelah introdujo originalmente y definir una teoría general de forcing iterado usando medidas finitamente aditivas. Además, se va a exponer una nueva constelación del digrama de Cichoń donde se separa el lado izquierdo, y el número de cubrimiento del ideal de los subconjuntos nulos de los números reales es singular.


Zoom meeting information.
Meeting ID: 856 1882 0721
Passcode: 123456

Cross-Alps Logic Seminar (speaker: Márton Elekes)

Cross-Alps Logic Seminar
On Friday 21.04.2023 at 16.00
Márton Elekes (Rényi Institute and Eötvös Loránd University)
will give a talk on 
On various notions of universally Baire sets

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Vincenzo

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon.

Our speaker this week will be Raphael Carroy from the University of Turin. This talk is going to take place this Friday, Apr. 21,  from 4pm to 5pm (UTC+8, Beijing time). 

Title: Continuous reducibility is a well-quasi-order on continuous functions with Polish 0-dimensional domains.

Abstract: Given topological spaces $X,X',Y,Y'$, and two functions $f:X\to Y$ and $f':X'\to Y'$, we say that $f$ \emph{reduces continuously} to $f'$ when there is a pair $(\sigma,\tau)$ of continuous functions such that $f=\tau\circ f'\circ\sigma$. This quasi-order has first been introduced by Weihrauch in the context of Computable Analysis at the beginning of the 1990s. It has recently received interest in Descriptive Set Theory.
With Yann Pequignot, we proved that on the class of continuous functions with Polish 0-dimensional domains, there are no infinite antichains and no infinite strictly descending chains for continuous reducibility. In other words, continuous reducibility is a well-quasi-order on this class of functions.
I will give some context for this result and outline the proof.


_________________________________________________________
Title : The 25th Nankai Logic Colloquium --Raphael Carroy
Time :16:00pm, Apr. 21, 2023 (Beijing Time) 
Zoom Number : 812 8606 8722
Passcode : 165561
Link : https://us02web.zoom.us/j/81286068722?pwd=V3V3NUpKNFgxQldLdEF1TW56WTNXQT09

_____________________________________________________________________


Best wishes,

Ming Xiao




This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 17, 2023 - - - -

Rutgers Logic Seminar 
Monday, April 17, 2pm, Rutgers University, Hill 005
Alejandro Poveda, CMSA Harvard
The Gluing Property


Logic and Metaphysics Workshop
Date: Monday, April 17, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Branden Fitelson (Northeastern).
Title: Probability and logic/meaning: Two approaches

Abstract: In this talk, I will compare and contrast two approaches to the relation between probability and logic/meaning.  First, I will examine the Traditional (“Kolmogorovian”) Approach of setting up probability calculi, which presupposes semantic/logical notions and defines conditional probability in terms of unconditional probability.  Then, I will discuss the Popperian Approach, which does not presuppose semantic/logical notions, and which takes conditional probability as primitive.  Along the way, I will also discuss the prospects (and pitfalls) of adding an Adams-style conditional to various probability calculi.




- - - - Tuesday, Apr 18, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 18, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Katarzyna W. Kowalik, University of Warsaw
The chain-antichain principle and proof size

The chain-antichain principle  is a well-known consequence of Ramsey's theorem for pairs and two colours . It says that for every partial order on  there exists an infinite chain or antichain with respect to this order. Both of these principles are -conservative over the weak base theory . Such conservation results usually prompt to ask about lengths of proofs. Kołodziejczyk, Wong and Yokoyama proved that  has a non-elementary speedup over  for proofs of  sentences. We show that the behaviour of  is the opposite: it can be polynomially simulated by  with respect to  sentences. Our argument uses a technique of forcing interpretation developed by Avigad. In the first step we syntactically simulate a construction of a generic computable ultrapower of a model of . Then we find a generic cut satisfying  inside the ultrapower.




- - - - Wednesday, Apr 19, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Walter Tholen, York University.

Date and Time:     Wednesday April 19, 2023, 7:00 - 8:30 PM. ZOOM TALK.

Title:     What does “smallness” mean in categories of topological spaces?


Abstract: Quillen’s notion of small object and the Gabriel-Ulmer notion of finitely presentable or generated object are fundamental in homotopy theory and categorical algebra. Do these notions always lead to rather uninteresting classes of objects in categories of topological spaces, such as the class of finite discrete spaces, or just the empty space , as the examples and remarks in the existing literature may suggest?

In this talk we will demonstrate that the establishment of full characterizations of these notions (and some natural variations thereof) in many familiar categories of spaces, such as those of T_i-spaces (i= 0, 1, 2), can be quite challenging and may lead to unexpected surprises. In fact, we will show that there are significant differences in this regard even amongst the categories defined by the standard separation conditions, with the T1-separation condition standing out. The findings about these specific categories lead us to insights also when considering rather arbitrary full reflective subcategories of Top.

(Based on joint work with J. Adamek, M. Husek, and J. Rosicky.)



- - - - Thursday, Apr 20, 2023 - - - -



- - - - Friday, Apr 21, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 21, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Mohammad Golshani, Institute for Research in Fundamental Sciences

The proper forcing axiom for -sized posets and the continuum

We discuss Shelah's memory iteration technique and use it to show that the PFA for posets of size  is consistent with large continuum. This is joint work with David Aspero.




Logic Workshop
CUNY Graduate Center
Friday April 21, 2:00pm-3:30pm, Room 6417
James Hanson, University of Maryland

How bad could it be? The semilattice of definable sets in continuous logic

Continuous first-order logic is a generalization of discrete first-order logic suited for studying structures with natural underlying metrics, such as operator algebras and -trees. While many things from discrete model theory generalize directly to continuous model theory, there are also new subtleties, such as the correct notion of 'definability' for subsets of a structure. Definable sets are conventionally taken to be those that admit relative quantification in an appropriate sense. An easy argument then establishes that the union of definable sets is definable, but in general the intersection of definable sets may fail to be. This raises the question of which semilattices arise as the partial order of definable sets in a continuous theory.

After giving an overview of the basic properties of definable sets in continuous logic, we will give a largely visual proof that any finite semilattice (and therefore any finite lattice) is the partial order of definable sets in some superstable continuous first-order theory. We will then discuss a partial extension of this to certain infinite semilattices.




Next Week in Logic at CUNY:

- - - - Monday, Apr 24, 2023 - - - -

Rutgers Logic Seminar 
Monday, April 24, 2pm, Rutgers University, Hill 005
Aristotelis Panagiotopoulos, CMU


Logic and Metaphysics Workshop
Date: Monday, April 24, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Andrea Iacona (Turin).
Title: Inferentialism and connexivity

Abstract: In my talk I will investigate the relationships between two claims about conditionals that by and large are discussed separately. One is the claim that a conditional holds when its consequent can be inferred from its antecedent, or when the latter provides a reason for accepting the former. The other is the claim that conditionals intuitively obey some characteristic connexive principles, such as Aristotle’s Thesis and Boethius Thesis. Following a line of thought that goes back to Chrysippus, I will suggest that these two claims may coherently be understood as distinct manifestations of a single basic idea, namely, that a conditional holds when its antecedent is incompatible with the negation of its consequent. The account of conditionals that I will outline is based precisely on this idea.



- - - - Tuesday, Apr 25, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 25, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Mateusz Łełyk University of Warsaw



- - - - Wednesday, Apr 26, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Dusko Pavlovic, University of Hawai‘i at Mānoa.

Date and Time:     Wednesday April 26, 2023, 7:00 - 8:30 PM. ZOOM TALK.

Title:     Program-closed categories.


Abstract: > Let CC be a symmetric monoidal category with a comonoid on every object. Let CC* be the cartesian subcategory with the same objects and just the comonoid homomorphisms. A *programming language* is a well-ordered object P with a *program closure*: a family of X-natural surjections
CC(XA,B) <<--run_X-- CC*(X,P)
one for every pair A,B. In this talk, I will sketch a proof that program closure is a property: Any two programming languages are isomorphic along run-preserving morphisms. The result counters Kleene's interpretation of the Church-Turing Thesis, which has been formalized categorically as the suggestion that computability is a structure, like a group presentation, and not a property, like completeness. We prove that it is like completeness. The draft of a book on categorical computability is available from the web site dusko.org.




- - - - Thursday, Apr 27, 2023 - - - -



- - - - Friday, Apr 28, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 28, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Will Boney Texas State University


- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 19th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet fixed, the preliminary plan is to look at some classical forcing results to broaden/refresh our education in the subject. Best, David

(KGRC) two talks on Thursday, April 20

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Sergei Starchenko (host: Matthias Aschenbrenner) visits the KGRC from April 16 to April 30 and gives a talk, details to be announced at a later time. Zoltán Vidnyánszky (host: Vera Fischer) visits the KGRC on April 20 and gives a talk, see below. Heike Mildenberger (host: Vera Fischer) visits the KGRC from May 3 to May 6 and gives a talk on May 4, details to be announced at a later time. Fabian Kaak (host: Vera Fischer) visits the KGRC from May 23 to May 26 and gives a short talk, details to be announced at a later time. Jaroslav Šupina (host: Vera Fischer) visits the KGRC from June 18 to June 24 and gives a talk, details to be announced at a later time. Nadiya Kolos (host: Miguel Moreno) visits the KGRC from June 19 to June 23 and gives a talk, details to be announced at a later time. * * * For a video recording of Martin Pinsker's talk, please see his slides at https://dmg.tuwien.ac.at/pinsker/talks/2023/pinsker_KGRC.pdf and a video recording at https://univienna.zoom.us/rec/share/rKNNyLly9EuERJbt_r2qp-71ktMjeAR5i5zFIq7HhA0g57kgC_T9tZs4VjMFJc85.fFpWWl1LZ8WHgVGg (use passcode ?yG874^^ to watch) * * * Set Theory Seminar Kurt Gödel Research Center Thursday, April 20 (Please note the unuasual day and time: Starting in April, most of the talks in the Set Theory Seminar will be moved to Thursday, 11:30am. A few will remain on Tuesday, 3:00pm however.) "Menger spaces everywhere" Lyubomyr Zdomskyy (TU Wien) Combinatorial covering properties, which arose from the study of classical special sets of reals, appear in many contexts in topology and set theory. In this talk we shall discuss some applications of the Menger property and certain stronger versions thereof. It is planned to be a gentle introduction to the next talk on April 27. Time and Place Talk at 11:30am in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk and the Zoom session to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Tuesday, April 20 "Homomorphism problems in the infinite context" Zoltán Vidnyánszky (Eötvös Loránd U, HU) The CSP dichotomy of Bulatov and Zhuk is a celebrated theorem of computer science: it states that given a finite structure H, deciding whether a structure G admits a homomorphism to G is either easy (in P) or hard (NP-complete). We will discuss two infinitary versions of this theorem. First, following Thornton, in the Borel con ext. Here a striking difference from the finite world emerges: we will show that solving linear equations over a finite field is already hard ($\Sigma^1_2$-complete). Second, assuming only ZF, we will consider the relationship of the H-compactness properties, that is, the statement that for every G if every finite substructure of G admits a homomorphism to H then so is G. Here we show that there exists a model M of ZF, such that M $\models$ H-compactness iff the H-homomorphism problem is easy. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please direct any other questions about this talk and the Zoom session to vera.fischer@univie.ac.at.

Fwd: Announcement - PhDs in Logic

Barcelona Logic Seminar

Dear colleagues, 

                                                                            We would like to announce the XIV edition of the conference PhDs in Logic 2023 that will take place in Granada, Spain, 4-6 october.
                                     
                                                    
There will be 6 keynote talks primarily aimed at PhD students and early career researchers.

Keynote speakers:
  • Tomás Ibarlucía - Université de Paris
  • Jordi López Abad - UNED
  • Nina Gierasimczuk - Danish Technical University
  • Amanda Vidal - IIIA - CSIC
  • Julian Murzy - University of Salzburg
  • María José Frápolli Sanz - Universidad de Granada

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


All participants are encouraged to submit an abstract (1000 words). In case it is accepted, the scientific committee will then decide if the abstract merits a 20 minutes presentation and the poster session, or just the poster session. 



----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



Student members of the Association for Symbolic Logic (ASL) may apply for travel support at ASL. Note that such applications have to be submitted at least 3 months prior to the meeting.

The "Sociedad de Lógica, Metodología y Filosofía de la Ciencia" also offers support for members. https://solofici.org/ayudas-a-jovenes-investigadores-para-la-asistencia-a-congresos-internacionales-2/



----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



See the webpage of the meeting for further information https://phdsinlogicxiv.com/ and do not hesitate to contact us at phdsinlogic@gmail.com.



Best,
Catalina Torres
Jose Santiago
Daira Pinto
Juan M Santiago

Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Charla de Luis Reyes en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

Abril 13

4:00 p.m. - 5:00 p.m. (hora de Colombia)  

 

Espacios de Johnson-Lindenstrauss y familias AD
Luis D. Reyes

Universidad Nacional Autónoma de México

 

Resumen. Los espacios de Johnson-Lindentrauss fueron introducidos por ambos autores en los años setentas como un contraejemplo 'artificial' a propiedades topológicas en análisis funcional. Sin embargo, el estudio de estos espacios ha llevado a entenderlos a través de familias casi ajenas (AD) y las compactaciones de su psi-espacio.

En esta charla, daremos un breve repaso de algunos resultados en esta línea de investigación, así como una introducción a los métodos que permiten traducir propiedades combinatorias de las familias AD a importantes propiedades topológicas de los espacios de Banach.


Zoom meeting information.
Meeting ID: 856 1882 0721
Passcode: 123456

Logic Seminar 12 April 2023 17:00 hrs at NUS by Daniel Hoffmann via Zoom

NUS Logic Seminar
Hello, here is some local talk at 16:00 hrs in which some of the local people might be interested. In order to avoid a clash, we start this talk at 17:15 hrs. Chieu Minh, please inform Daniel. Regards, Frank On Mon, Apr 10, 2023 at 04:05:19PM +0800, Frank STEPHAN wrote: > Invitation to the Logic Seminar at the National University of Singapore > > Date: Wednesday, 12 April 2023, 17:00 hrs > > Place: Talk via Zoom: > https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 > Meeting ID: 830 4925 8042 > Passcode: 1729=x3+y3 > > Speaker: Daniel Hoffmann > > Title: Model completeness of SL(2,R) > > URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html > > I will present some results from my joint project with Chieu Minh > Tran and Jinhe Ye. Model completeness is a weakening of quantifier > elimination. The main task here is to define a field in the structure > of the pure group, but in such a way that this definition transfers > over some group extensions. I will recall basic facts from the model > theory needed here and similar recent results in the field, then - > hopefully - I will be able to sketch the idea of the proof, which is > quite geometric. >

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 10, 2023 - - - -

Rutgers Logic Seminar - TODAY'S SEMINAR CANCELLED

*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***


- - - - Tuesday, Apr 11, 2023 - - - -

*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***


- - - - Wednesday, Apr 12, 2023 - - - -

*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***


- - - - Thursday, Apr 13, 2023 - - - -

*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***



- - - - Friday, Apr 14, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 14, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Gabriel Goldberg, University of California, Berkeley
TBA



Next Week in Logic at CUNY:

- - - - Monday, Apr 17, 2023 - - - -

Rutgers Logic Seminar 
Monday, April 17, 2pm, Rutgers University, Hill 005
Alejandro Poveda, CMSA Harvard



Logic and Metaphysics Workshop
Date: Monday, April 17, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Branden Fitelson (Northeastern).
Title: Probability and logic/meaning: Two approaches

Abstract: In this talk, I will compare and contrast two approaches to the relation between probability and logic/meaning.  First, I will examine the Traditional (“Kolmogorovian”) Approach of setting up probability calculi, which presupposes semantic/logical notions and defines conditional probability in terms of unconditional probability.  Then, I will discuss the Popperian Approach, which does not presuppose semantic/logical notions, and which takes conditional probability as primitive.  Along the way, I will also discuss the prospects (and pitfalls) of adding an Adams-style conditional to various probability calculi.




- - - - Tuesday, Apr 18, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 18, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Katarzyna W. Kowalik, University of Warsaw


- - - - Wednesday, Apr 19, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Walter Tholen, York University.

Date and Time:     Wednesday April 19, 2023, 7:00 - 8:30 PM. ZOOM TALK.

Title:     What does “smallness” mean in categories of topological spaces?


Abstract: Quillen’s notion of small object and the Gabriel-Ulmer notion of finitely presentable or generated object are fundamental in homotopy theory and categorical algebra. Do these notions always lead to rather uninteresting classes of objects in categories of topological spaces, such as the class of finite discrete spaces, or just the empty space , as the examples and remarks in the existing literature may suggest?

In this talk we will demonstrate that the establishment of full characterizations of these notions (and some natural variations thereof) in many familiar categories of spaces, such as those of T_i-spaces (i= 0, 1, 2), can be quite challenging and may lead to unexpected surprises. In fact, we will show that there are significant differences in this regard even amongst the categories defined by the standard separation conditions, with the T1-separation condition standing out. The findings about these specific categories lead us to insights also when considering rather arbitrary full reflective subcategories of Top.

(Based on joint work with J. Adamek, M. Husek, and J. Rosicky.)



- - - - Thursday, Apr 20, 2023 - - - -



- - - - Friday, Apr 21, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 14, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Mohammad Golshani, Institute for Research in Fundamental Sciences
TBA


Logic Workshop
CUNY Graduate Center
Friday April 21, 2:00pm-3:30pm, Room 6417
James Hanson, University of Maryland
TBA


- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Chris Laskowski from the University of Maryland. This talk is going to take place this Friday, Apr. 14,  from 9am to 10am(UTC+8, Beijing time). 


Title:  On the Borel complexity of modules

Abstract:  We prove that among all countable, commutative rings R (with unit) the theory of R-modules is not Borel complete if and only if there are only countably many non-isomorphic countable R-modules.  From the proof, we obtain a succinct proof that the class of torsion free abelian groups is Borel complete.
   The results above follow from some general machinery that we expect to have applications in other algebraic settings.  Here, we also show that for an arbitrary countable ring R, the class of left R-modules equipped with an endomorphism is Borel complete; as is the class of left R-modules equipped with predicates for four submodules.  This is joint work with Danielle Ulrich.



_________________________________________________________

Title : The 24th Nankai Logic Colloquium --Chris Laskowski
Time : 9:00am, Apr. 14, 2023 (Beijing Time) 
Zoom Number : 836 6352 7223
Passcode : 673161

_____________________________________________________________________


Best wishes,

Ming Xiao




Logic Seminar 12 April 2023 17:00 hrs at NUS by Daniel Hoffmann via Zoom

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 12 April 2023, 17:00 hrs Place: Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Daniel Hoffmann Title: Model completeness of SL(2,R) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html I will present some results from my joint project with Chieu Minh Tran and Jinhe Ye. Model completeness is a weakening of quantifier elimination. The main task here is to define a field in the structure of the pure group, but in such a way that this definition transfers over some group extensions. I will recall basic facts from the model theory needed here and similar recent results in the field, then - hopefully - I will be able to sketch the idea of the proof, which is quite geometric.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 12th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Martin Balko -- On ordered Ramsey numbers The ordered Ramsey number of an ordered graph G^< (that is, graph with a fixed linear ordering of its vertices) is the smallest positive integer N such that every 2-coloring of the edges of ordered K^

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the afternoon.


Our speaker this week will be David Schritesser from Harbin Institute of Technology. This talk is going to take place this Friday,  Apr 07 ,  from 4pm to 5pm(UTC+8, Beijing time). 

Title: Definability of Maximal Cofinitary Groups

Abstract: The notion of a cofinitary groups was named by Peter Cameron in the 1980ies, as a dual to the notion of finitary permutation groups. Cameron asked about such groups which are maximal in the sense that they are not proper subgroups of another cofinitary group. It was long thought that such maximal cofinitary groups are necessarily extremely complicated objects.

In 2016, Horowitz and Shelah showed that there is a Borel maximal cofinitary group. I recent joint work with my student Severin Mejak, that there is even an F_sigma such group, which is isomorphic to a free group. Among free maximal cofinitary groups, this is the lowest possible complexity. In this talk, I will give some ideas of the proof.

___________________________________________________________________________________________________________________________________________________


This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title : The 23rd Nankai Logic Colloquium --David Schrittesser

Time : 16:00pm, Apr. 07, 2023 (Beijing Time) 

Zoom Number : 867 3454 6492

Passcode : 766848

_____________________________________________________________________


Best wishes,

Ming Xiao




This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 3, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 3, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Thomas Ferguson (Czech Academy of Sciences).
Title: Care-theoretic semantics: Problems and non-deterministic solutions

Abstract: In this talk I will present the details of a project of care-theoretic semantics in which a linguistic feature of care–rather than truth–is understood as the fundamental semantic property. I will review the details, including how adopting a bounds consequence position in which bounds are determined by considerations of topic allows one to determine both a theory of inference and theory of meaning on the basis of care alone. I will consider two challenges to the project: that of the reconciliation of topic-theoretic and truth-theoretic bounds (in which we need to acknowledge cases in which a position crosses both types of bounds) and sui generis monstrous content (in which two anodyne sentences together yield a content-theoretic violation). I will show that in both cases intuitions suggest the use of Nmatrices in the style of Avron and consider the merits of their employment in the care-theoretic setting.



- - - - Tuesday, Apr 4, 2023 - - - -



- - - - Wednesday, Apr 5, 2023 - - - -

*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***


- - - - Thursday, Apr 6, 2023 - - - -



- - - - Friday, Apr 7, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 7, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Miha Habič, Bard College at Simon's Rock

Some old and new results on nonamalgamable forcing extensions

Fixing some countable transitive model  of set theory, we can consider its generic multiverse, the family of all models obtainable from  by taking any sequence of forcing extensions and ground models. There is an attractive similarity between the generic multiverse and the Turing degrees, but the multiverse has the drawback (or feature?) that it contains nonamalgamable models, that is, models with no common upper bound, as was observed by several people, going back to at least Mostowski. In joint work with Hamkins, Klausner, Verner, and Williams in 2019, we studied the order-theoretic properties of the generic multiverse and, among other results, gave a characterization of which partial orders embed nicely into the multiverse. I will present our results in the simplest case of Cohen forcing, as well as existing generalizations to wide forcing, and some new results on non-Cohen ccc forcings.



*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***


Next Week in Logic at CUNY:

- - - - Monday, Apr 10, 2023 - - - -

Rutgers Logic Seminar
Monday, April 10, 2pm, Rutgers University, Hill 005
Victoria Gitman, CUNY
Jensen's forcing at an inaccessible


- - - - Tuesday, Apr 11, 2023 - - - -



- - - - Wednesday, Apr 12, 2023 - - - -



- - - - Thursday, Apr 13, 2023 - - - -

*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***



- - - - Friday, Apr 14, 2023 - - - -



- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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To subscribe/unsubscribe to this list, please email your request to Jonas.Reitz12@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email Jonas.Reitz12@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 5th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- On AD families of subsets of the rational numbers We will talk about some basic properties of almost disjoint families modulo the ideal of nowhere dense sets. Best, David

Logic Seminar 5 April 2023 17:00 hrs at NUS by Frank Stephan

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 5 April 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#05-11 Speaker: Frank Stephan Title: Languages given by finite automata over the unary alphabet URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Languages over the unary alphabet have been studied in computer science for a long time. The present work investigates regular languages over the unary alphabet and one investigates the various forms of representing them by finite automata. Here three types of automata are studied: (a) Deterministic finite automata where the finite automaton has exactly one run per word which is accepting iff the word is in the given language. (b) Nondeterministic finite automata where there are choices in the states on how to procede with a run on various symbols, a word is in the language iff there is some run which is accepting. (c) Unambiguous finite automata which are a special case of nondeterministic finite automata and which either reject a word or which have exactly one accepting run for a word. The results presented are from the following two areas: (1) This paper improves the upper bound of the equality problem of unary nondeterministic automata from an exponential in the second root to an exponential in the third root of the number of states. This almost matches a known lower bound based on the exponential time hypothesis by Fernau and Krebs. (2) It is established that the standard regular operations of union, intersection, complementation and Kleene star cause either only a polynomial or a quasipolynomial blow-up. Concatenation of two n-state ufas, in worst case, causes a blow-up from n to a function with an exponent of sixth root of n. Decision problems of finite formulas using regular operations and comparing languages given by n-state unambiguous automata, in worst case, require an exponential-type of time under the Exponential Time hypothesis and this complexity goes down to quasipolynomial time in the case that the concatenation of languages is not used in the formula. Merely comparing two languages given by n-state ufas in Chrobak Normal Form is in LOGSPACE. This talk is joint work with Gordon Hoi, Sanjay Jain and Christopher Tan.

Core Model Seminar next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, April 4, 2023

Core Model Seminar:  1:30 - 3 PM Eastern, Online, Martin Zeman, University of California, Irvine

Join Zoom Meeting: https://cmu.zoom.us/j/97749733438?pwd=Yk5PcSsvekptWWxMNUhCU2pFbzA0Zz09
Meeting ID: 977 4973 3438
Passcode: 457791

TITLE: Distributivity of iterated club shooting and fine structural
models, part 1

ABSTRACT: Iterative adding closed unbounded sets through stationary sets found quite a few applications in set theory. One natural way to do this is adding club sets using posets consisting of initial segments of the desired clubs. In such situations, one important property of such iterations is sufficient amount of distributivity. In fact, establishing distributivity is often the main part of arguments that involve iterated club shooting.

There are two possible situations where one iteratively adds clubs.
First, for a fixed cardinal $\kappa$, one iteratively adds club subsets
of $\kappa^+$. This kind of construction proved to have many applications. Second, one may start with a cardinal $\delta$ and
iteratively add club subsets of cardinals $\kappa^+$ where $\kappa$
ranges over some set above $\delta$. Surprisingly, this kind of construction has not been much studied. In this talk we will focus on this situation.

In order to add a club subset of some stationary set $S$ the set $S$
must be large in a certain sense; such sets are called fat. It is known
that, consistently, iteratively adding club subsets of fat stationary sets
of $\omega_n$ on a tail-end of $n\in\omega$ followed by forming an
inverse limit at the end may collapse $\aleph_n$ to $\omega$. A strong form of fatness is the property of being the complement of a
non-reflecting stationary set. One can prove, using a fairly standard
argument, that if the iteration described above uses complements of
non-reflecting stationary sets instead of just fat sets, then such an
iteration is $(\omega_{n+1},\infty)$-distributive where $\omega_n$ is
the first active step in the iteration. One can also prove in ZFC that
the analogous  amount of distributivity holds of longer iterations,
where the first active step is at $\delta$ and inverse limits are used
at singular steps, as long as the singular steps are of cofinality
$<\delta$. Passing through singular steps of cofinality $\ge\delta$
seems to be difficult, and we only know how to do this over a fine
structural model where the non-reflecting stationary sets are carefully
chosen. Even in such a seemingly special case, the method does have applications.

This is a part of a joint work of Foreman-Magidor-Zeman on games with filters.

Charla de Daniel Calderón en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

Marzo 30

4:00 p.m. - 5:00 p.m. (hora de Colombia)  

 

La conjetura de Borel y conjuntos magro-aditivos
Daniel Calderón

Universidad de Toronto

 

Resumen. Los conjuntos fuertemente nulos fueron introducidos por Borel y han sido estudiados desde comienzos del siglo pasado. Borel conjeturó que todo conjunto fuertemente nulo de reales debe ser contable. Algunos años más tarde, Sierpiński demostró que asumiendo CH existe un conjunto fuertemente nulo no contable. Sin embargo, la pregunta por la consistencia relativa a ZFC de la conjetura de Borel siguió irresoluta hasta que en 1976 Laver construyó, en un trabajo innovador, un modelo de ZFC en el que todo conjunto fuertemente nulo de reales es contable.

Un resultado debido a Galvin, Mycielski y Solovay, provee una caracterización de nulidad fuerte en términos de una propiedad algebraica para subconjuntos de la recta real. Utilizando esta caracterización, la noción de magro-aditividad apareció en escena. La magro-aditividad, al igual que otras nociones de pequeñes en la recta real, han recibido especial atención en años recientes. Una pregunta de 1993, debida a Bartoszyński y Judah, cuestiona si los conjuntos fuertemente nulos y los conjuntos magro-aditivos tienen una muy rígida relación en el sentido siguiente:
Pregunta (Bartoszyński–Judah, 1993): ¿Si todo subconjunto fuertemente nulo de la recta real es magro-aditivo, necesariamente vale la conjetura de Borel? 
En esta charla daré algunos detalles sobre la consistencia relativa de una respuesta negativa a la pregunta de Bartoszyński y Judah, construyendo un modelo de ZFC en el que todo conjunto fuertemente nulo de reales es magro-aditivo y la conjetura de Borel falla.


Zoom meeting information.
Meeting ID: 856 1882 0721
Passcode: 123456

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the afternoon.


Our speaker this week will be Samuel Coskey from Boise State University. This talk is going to take place this Friday, Mar 31,  from 16:00 to 17:00(UTC+8, Beijing time). 

Title: Borel classification of conjugacy problems

Abstract: We aim to study the complexity of conjugacy problems for automorphisms of countable graphs G. Since conjugacy is an equivalence relation on Aut(G), we will study complexity using the invariant descriptive set theory, that is, the Borel reducibility hierarchy. After introducing this background setup, we will give a series of examples of locally finite graphs G whose conjugacy problems have a variety of different complexities. We will see conjugacy problems which are smooth (completely classifiable), complete for hyperfinite relations (E0), complete for essentially countable Borel equivalence relations (E_infinity), and intermediate between E0 and E_infinity.

___________________________________________________________________________________________________________________________________________________


This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title : The 22nd Nankai Logic Colloquium --Samuel Coskey

Time : 16:00pm, Mar. 31, 2023 (Beijing Time) 

Zoom Number : 830 5925 5547

Passcode : 890764

Link : https://us02web.zoom.us/j/83059255547?pwd=V29IcGo0bWdyeitRdHc5eUhBSnNrQT09

_____________________________________________________________________


Best wishes,

Ming Xiao




Cross-Alps Logic Seminar (speaker: Ludovic Patey)

Cross-Alps Logic Seminar
On Friday 31.03.2023 at 16.00
Ludovic Patey (CNRS)
will give a talk on 
Canonical notions of forcing in Reverse Mathematics

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Vincenzo

Logic Seminar Wednesday 29 March 2023 17:00 hrs at NUS by Xie Ruofei

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 29 March 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#05-11 Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Xie Ruofei Title: Majorising the Optimal C.E. Supermartingale URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html In the article "Highness Properties Close to PA-Completeness", Greenberg, Miller and Nies left the following questions: (1) Is there a finite collection of functionals {Gamma_i:i

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 27, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 27, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Gregory Taylor (CUNY)
Title: First-order logics over fixed domain

Abstract: What we call first-order logic over fixed domain was initiated, in a certain guise, by Peirce around 1885 and championed, albeit in idiosyncratic form, by Zermelo in papers from the 1930s.  We characterize such logics model- and proof-theoretically and argue that they constitute exploration of a clearly circumscribed conception of domain-dependent generality.  Whereas a logic, or family of such, can be of interest for any of a variety of reasons, we suggest that one of those reasons might be that said logic fosters some clarification regarding just what qualifies as a logical concept, a logical operation, or a logical law.



- - - - Tuesday, Mar 28, 2023 - - - -



- - - - Wednesday, Mar 29, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Jim Otto.

Date and Time:     Wednesday March 29, 2023, 7:00 - 8:30 PM. ZOOM TALK

Title:     P Time, A Bounded Numeric Arrow Category, and Entailments.


Abstract: We revisit the characterization of the P Time functions from our McGill thesis.

1. We build on work of L. Roman (89) on primitive recursion and of A. Cobham (65) and Bellantoni-Cook(92) on P Time.

2. We use base 2 numbers with the digits 1 & 2. Let N be the set of these numbers. We split the tapes of a multi-tape Turing machine each into 2 stacks of digits 1 & 2. These are (modulo allowing an odd numberof stacks) the multi-stack machines we use to study P Time.

3. Let Num be the category with objects the finite products of N and arrows the functions between these. From its arrow category Num^2 we abstract the doctrine (here a category of small categories with chosen structure) PTime of categories with with finite products, base 2 numbers, 2-comprehensions, flat recursion, & safe recursion. Since PTime is a locally finitely presentable category, it has an initial category I. Our characterization is that the bottom of the image of I in Num^2 consists of the P Time functions.

4. We can use I (thinking of its arrows as programs) to run multi-stack machines long enough to get P Time.This is the completeness of the characterization.

5. We cut down the numeric arrow category Num^2, using Bellantoni-Cook growth & time bounds on the functions, to get a bounded numeric arrow category B. B is in the doctrine PTime. This yields the soundness of the characterization.

6. For example, the doctrine of toposes with base 1 numbers, choice, & precisely 2 truth values (which captures much of ZC set theory) likely lacks an initial category, much as there is an initial ring, but no initial field.

7. On the other hand, the L. Roman doctrine PR of categories with finite products, base 1 numbers, & recursion (that is, product stable natural numbers objects) does have an initial category as it consists of the strong models of a finite set of entailments. And is thus locally finitely presentable. We sketch the signature graph for these entailments. And some of these entailments. Similarly (but with more complexity) there are entaiments for the doctrine PTime.





- - - - Thursday, Mar 30, 2023 - - - -



- - - - Friday, Mar 31, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 31, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.

Benjamin Goodman, CUNY
-correct forcing axioms

The standard method of producing a model of a forcing axiom from a supercompact cardinal in fact gives a model of an even stronger principle: that for every small name a and every  formula  such that  is forceable by and preserved under further forcing in our forcing class, there is a filter  which meets a desired collection of dense sets and also interprets a such that  already holds. I will show how to generalize this result to formulas of higher complexity by starting with slightly stronger large cardinal assumptions, then discuss the bounded versions of these enhanced forcing axioms, their relationships to other similar principles, and their consequences.




Logic Workshop
CUNY Graduate Center
Friday March 31, 2:00pm-3:30pm, Room 6417

Corey Switzer, University of Vienna
Galois-Tukey reductions and canonical structure in the Cichoń diagram

Cardinal invariants of the continuum are cardinal numbers which, roughly, measure how 'badly' CH fails in various mathematical contexts such as analysis and topology. For instance the cardinal  is the least  for which there are  many Lebesgue measure zero sets of reals whose union is not measure zero. Classical facts imply  but the precise value is undetermined in ZFC and depends heavily on the axioms of set theory. Other numbers follow a similar pattern of 'the least size of a set of reals (Borel sets, etc) lacking a classical smallness property'.

The Cichoń diagram displays cardinal invariants related to Lebesgue measure (the null ideal), Baire category (the meager ideal) as well as the bounding and dominating numbers which concern growth rates of functions. Many surprising ZFC-inequalities exist between these cardinals suggesting a rich world living on the reals in various models of set theory. At the combinatorial heart of every proof of a ZFC inequality derives from a Galois-Tukey reduction: the (ZFC-provable) existence of a pair of continuous maps with simple properties that make sense outside of the context of logic and indeed would be sensible to any analyst or topologist.

In this talk we will discuss some recent work in progress on the descriptive complexity of maps witnessing consistent but non-provable implications. We will show using largely computability theoretic methods that in Gödel's constructible universe there are low level projective reductions between any two cardinal invariants - thus CH holds in a very 'definable' way, while in Solovay's model of 'all sets of reals are Lebesgue measurable' (and therefore the axiom of choice fails) there are no non-ZFC provable implications thus these cardinals are all as different as possible.





Next Week in Logic at CUNY:

- - - - Monday, Apr 3, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 3, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Thomas Ferguson (Czech Academy of Sciences).
Title: Care-theoretic semantics: Problems and non-deterministic solutions

Abstract: In this talk I will present the details of a project of care-theoretic semantics in which a linguistic feature of care–rather than truth–is understood as the fundamental semantic property. I will review the details, including how adopting a bounds consequence position in which bounds are determined by considerations of topic allows one to determine both a theory of inference and theory of meaning on the basis of care alone. I will consider two challenges to the project: that of the reconciliation of topic-theoretic and truth-theoretic bounds (in which we need to acknowledge cases in which a position crosses both types of bounds) and sui generis monstrous content (in which two anodyne sentences together yield a content-theoretic violation). I will show that in both cases intuitions suggest the use of Nmatrices in the style of Avron and consider the merits of their employment in the care-theoretic setting.



- - - - Tuesday, Apr 4, 2023 - - - -



- - - - Wednesday, Apr 5, 2023 - - - -

*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***


- - - - Thursday, Apr 6, 2023 - - - -



- - - - Friday, Apr 7, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 7, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Miha Habič, Bard College at Simon's Rock



*** April 5-13, 2023 Spring Recess CUNY Graduate Center ***



- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to Jonas.Reitz12@citytech.cuny.edu.

If you have a logic-related event that you would like included in future mailings, please email Jonas.Reitz12@citytech.cuny.edu.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 29th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Peter Vojtáš -- Considerations on Galois--Tukey motivated by complexity theory and reverse mathematics We will try to walk through the landscape motivated by following publications Peter Vojtas. Generalized Galois-Tukey connections between explicit relations on classical objects of real analysis, IMCP 6 (1993) 619-643 Andreas Blass. Questions and Answers -- A Category Arising in Linear Logic, Complexity Theory, and Set Theory, LMSLN 222 (1995) 61-81 Damir D. Dzhafarov , Carl Mummert. Reverse Mathematics - Problems, Reductions, and Proofs, Springer 2022 to perceive different phenomena, hoping to formulate some new observations and problems Considerations on Galois--Tukey motivated by complexity theory and reverse mathematics. Best, David

(KGRC) guests, video recordings and notes, and four talks

Kurt Godel Research Center
The KGRC welcomes as guests: Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Franz-Viktor Kuhlmann (host: Matthias Aschenbrenner) visits the KGRC from March 27 to March 31. José Nicolás Nájar Salinas (host: Miguel Moreno) visits the KGRC and gives a talk on March 29, see below. Sergei Starchenko (host: Matthias Aschenbrenner) visits the KGRC from April 16 to April 30 and gives a talk, details to be announced at a later time. Zoltán Vidnyánszky (host: Vera Fischer) visits the KGRC on April 20 and gives a talk, details to be announced at a later time. Fabian Kaak (host: Vera Fischer) visits the KGRC from May 23 to May 26 and gives a short talk, details to be announced at a later time. Jaroslav Šupina (host: Vera Fischer) visits the KGRC from June 18 to June 24 and gives a talk, details to be announced at a later time. Nadiya Kolos (host: Miguel Moreno) visits the KGRC from June 19 to June 23 and gives a talk, details to be announced at a later time. * * * video recordings and slides: For a video recording of part 1 of Miguel Moreno's tutorial, please use https://univienna.zoom.us/rec/share/0CoE9CuBiOXjuXf9dMiFnu63mp4xQCYvQSzjDNFeQT9edwtb9hVwDO6PvBXhSUaH.agwwTP4Mj8fEhKRn and passcode W^9Ej.h3 For part 2, please use https://univienna.zoom.us/rec/share/ltSirTm_O_ONGvGOu-9yJavOaG9QrihlrRtgWNixtSbZZtFTH4gaN7NliBodw44R.dEi0C8qkgxq__Sxp and passcode d3P&V1g$ Notes for the series so can be found here (and will also be updated here after part 3 will be delivered): https://mathematik.univie.ac.at/fileadmin/user_upload/f_mathematik/Events_News/Vortraege_Events/2023-24/KGRC_Set_Theory_2023-03_Miguel_Moreno.pdf For a video recording of Silvain Rideau-Kikuchi's talk, please use https://univienna.zoom.us/rec/share/WZ_GtG4tfySmIRU_O2axDtut8U8bxqNznZvCwk0rFd1nODm43gNH_UNMZUYdmV3j.-1kMmpCZag-qvkL6 and passcode @d1yoKnn * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, March 28 "Generalised Descriptive Set Theory, part III" Miguel Moreno (KGRC) During this talk we will discuss where in the generalized Borel-reducibility hierarchy are the isomorphism relation of first order complete theories. These theories are divided into two kinds: classifiable and non-classifiable. To study the classifiable theories case is needed the use of Ehrenfeucht-Frass games. On the other hand the study of the non-classifiable theories is done by using colored ordered trees. The goal of the talk is to see the classifiable theories case and sketch the ideas of non-classifiable theories. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Students at Uni Wien are required to attend in person.) Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Mathematical Colloquium Institut für Mathematik Wednesday, March 29 "Independence Phenomena in Mathematics: Current Obstacles and Scenarios for Solutions" Sandra Müller (TU Wien) The standard axioms of set theory, the Zermelo-Fraenkel axioms (ZFC), do not suffice to answer all questions in mathematics. While this follows abstractly from Kurt Gödel's famous incompleteness theorems, we nowadays know numerous concrete examples for such questions. A large number of problems in set theory, for example, regularity properties such as Lebesgue measurability and the Baire property are not decided - for even rather simple (for example, projective) sets of reals - by ZFC. Even many problems outside of set theory have been shown to be unsolvable, meaning neither their truth nor their failure can be proven from ZFC. A major part of set theory is devoted to attacking this problem by studying various extensions of ZFC and their properties. I will outline some of these extensions and explain current obstacles in understanding their impact on the set theoretical universe together with recent progress on these questions and future scenarios. This work is related to the overall goal to identify the "right" axioms for mathematics. Time and Place Coffee at 2:45pm Talk at 3:15pm Vinum cum Pane following the talk Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 12th floor Sky Lounge Please direct any questions about this talk to anton.mellit@univie.ac.at or jose.luis.romero@univie.ac.at. * * * Model Theory Research Seminar Kurt Gödel Research Center Wednesday, March 29 "Definability In Abstract Elementary Classes" José Nicolás Nájar Salinas (Fundación Universidad América, CO) The development of definability in the context of Abstract Elementary Classes has been boosted by the recent work of Shelah and Villaveces in which they prove that for every AEC $\mathcal{K}$ in a vocabulary $\tau$, there is a sentence $\psi\in\mathbb{L}_{\beth_2(\kappa)^{+++},\kappa}(\tau)$ axiomatizing where $\kappa$ is the Löwenheim-Skolem number of the class. Vasey enlarges $\tau$ to $\Tilde{\tau}$ and proves that if the AEC is tame and type-short, there is a bijection between the Galois Types of the AEC and the quantifier free types in an infinitary logic $\mathbb{L}_{\lambda,\lambda}(\Tilde{\tau})$ for some suitable $\lambda$, the semantic-syntactic correspondence. We extend the ideas of Vasey to make a partial semantic-syntactic correspondence-like results between Galois types and some types of the logic $\mathbb{L}_{\beth_2(\kappa)^{+++},\kappa}(\tau)$. Part of this is joint work with Andrés Villaveces. Time and Place Talk at 3:00pm Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, March 30 "Constraint Satisfaction Problems: algebraic and model-theoretic challenges to distinguish the easy from the hard" Michael Pinsker (TU Wien) I will give a gentle introduction to current algebraic and model-theoretic methods in the computational complexity of Constraint Satisfaction Problems (CSPs). A CSP is a computational problem where we are given variables and constraints about them; the question is whether the variables can be assigned values such that all constraints are satisfied. Numerous natural computational problems, such as satisfiability of a given system of equations over a field, are CSPs; in fact, any computational problem is Turing-equivalent to a CSP. Any CSP can be modeled by a relational structure, and conversely every relational structure naturally defines a CSP. In view of humanity's continuing quest to distinguish easy from hard problems in general, and the class P (polynomial-time solvable problems, e.g. satisfiability of linear equations over a field) from the class NP (polynomial-time verifiable problems, e.g. satisfiability of a propositional formula) in particular, the question arises which mathematical properties of a relational structure make the corresponding CSP easy and which make it hard. It turns out that particular algebraic invariants of the structure often determine the borderline between different complexity classes. Hence algebraic methods, combined with concepts from model theory as well as from Ramsey theory in the case of infinite structures, yield appropriate tools to determine the computational complexity of CSPs. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Students at Uni Wien are required to attend in person.) Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at.

Charla de Slawomir Solecki en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

March 23

4:00 p.m. - 5:00 p.m. (Colombia time)  

 

Descriptive set theory and closed groups generated by measure preserving transformations
Slawomir Solecki

Cornell University

 

Abstract. The talk is about applications of Descriptive Set Theory to Ergodic Theory. 

The behavior of a measure preserving transformation, even a generic one, is highly non-uniform. In contrast to this observation, a different picture of a very uniform behavior of the closed group generated by a generic measure preserving transformation $T$ has emerged. This picture included substantial evidence that pointed to these groups (for a generic $T$) being all topologically isomorphic to a single group, namely, $L^0$---the topological group of all Lebesgue measurable functions from $[0,1]$ to the circle. In fact, Glasner and Weiss asked if this is the case. 

We will describe the background touched on above, including the descriptive set theoretic background. We will indicate a proof of the following theorem that answers the Glasner--Weiss question in the negative: for a generic measure preserving transformation $T$, the closed group generated by $T$ is not topologically isomorphic to $L^0$. 



Zoom meeting information.
Meeting ID: 856 1882 0721
Passcode: 123456

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the morning.


Our speaker this week will be Christian Rosendal from the University of Maryland. This talk is going to take place this Friday,  Mar.24 ,  from 9am to 10am(UTC+8, Beijing time). 

Title: Amenability, optimal transport and cohomology of Banach modules

Abstract: Using tools from the theory of optimal transport, four results concerning isometric actions of amenable topological groups with potentially unbounded orbits are established. Specifically, consider an amenable topological group $G$ with no non-trivial homomorphisms to $\mathbb R$.
If $d$ is a compatible left-invariant metric on $G$, $E\subseteq G$ is a finite subset and $\epsilon>0$, there is a finitely supported probability measure $\beta$ on $G$ so that
$$
\max_{g,h\in E}\, {\sf W}(\beta g, \beta h)<\eps,
$$
where ${\sf W}$ denotes the {\em Wasserstein} or {\em optimal transport} distance between probability measures on the metric space $(G,d)$. When $d$ is the word metric on a finitely generated group $G$, this strengthens a well known theorem of H. Rei\-ter \cite{reiter}. Furthermore, when $G$ is locally compact, $\beta$ may be replaced by an appropriate probability density $f\in L^1(G)$.

Also, when $G\curvearrowright X$ is a continuous isometric action  on a metric space, the space of Lipschitz functions on the quotient $X/\!\!/G$ is isometrically isomorphic to a $1$-complemented subspace of the Lipschitz functions on $X$. And finally every continuous affine isometric action of $G$ on a Banach space has a canonical invariant linear subspace.
These results generalise previous theorems due to Schneider--Thom  and C\'uth--Doucha.

___________________________________________________________________________________________________________________________________________________


This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title : The 21st Nankai Logic Colloquium --Christian Rosendal 

Time : 9:00am, Mar. 24, 2023 (Beijing Time) 

Zoom Number : 849 1206 9207 

Passcode : 929100 

Link : https://zoom.us/j/84912069207?pwd=TTBWakY4OE9sdVNuN2dza3IvemY3Zz09 Christia

_____________________________________________________________________


Best wishes,

Ming Xiao




Logic Seminar Wed 22 March 2023 17:00 hrs at NUS by Takayuki Kihara

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 22 March 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#05-11 Speaker: Kihara Takayuki Title: Topos-theoretic aspect of the degrees of unsolvability URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: In this talk, we examine the topos-theoretic aspect of the degrees of (computable) unsolvability. One of the main interpretations of constructive mathematics is Kleene's realizability interpretation, which, as is well known, can be relativized by an oracle. In this sense, an oracle can be a factor that causes a change in a model of constructive mathematics. Let us review this observation from another point of view: there is a topos, called the effective topos, based on Kleene's realizability interpretation. And relativizing the realizability interpretation to an oracle yields a subtopos of the effective topos. Thus, the structure of oracles, i.e., the structure of the degrees of unsolvability, is expected to be closely related to the structure of the subtoposes of the effective topos. In this talk, we give a complete correspondence, in a strict sense, between the structure of the degrees of unsolvability and the structure of subtoposes of the effective topos (or its relatives).

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 20, 2023 - - - -

Rutgers Logic Seminar 
Monday, March 20, 2pm, Rutgers University, Hill 005
Roman Kossak, CUNY
Absolute Undefinability



Logic and Metaphysics Workshop
Date: Monday, March 20th, 4.15-6.15 (NY time), GC Room 9205
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Speaker: Shawn Simpson (Pitt)
Title: Logic and inference in the sender-receiver model

Abstract: The sender-receiver model was developed by David Lewis to tackle the question of the conventionality of meaning. But many people who cared about the conventionality of meaning did so because they thought it was intimately connected to the conventionality of logic. Since Lewis’s work, only a few attempts have been made to say anything about the nature of logic and inference from the perspective of the sender-receiver model. This talk will look at the what’s been said in that regard, by Skyrms and others, and suggest a few general lessons.



- - - - Tuesday, Mar 21, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, March 21, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Bartosz Wcisło, University of Gdańsk
Satisfaction classes with the full collection scheme

Satisfaction classes are subsets of models of Peano arithmetic which satisfy Tarski's compositional clauses. Alternatively, we can view satisfaction or truth classes as the extension of a fresh predicate T(x) (the theory in which compositional clauses are viewed as axioms is called CT^-).

It is easy to see that CT^- extended with a full induction scheme is not conservative over PA, since it can prove, for instance, the uniform reflection over arithmetic. By a nontrivial argument of Kotlarski, Krajewski, and Lachlan, the sole compositional axioms of CT^- in fact form a conservative extension of PA. Moreover, in order to obtain non-conservativity it is enough to add induction axioms for the Delta_0 formulae containing the truth predicate.

Answering a question of Kaye, we will show that the theory of compositional truth, CT^- with the full collection scheme is a conservative extension of Peano Arithmetic. Following the initial suggestion of Kaye, we will in fact show that any countable recursively saturated model M of PA has an elementary omega_1-like end extension M' such that M' carries a full satisfaction class.



- - - - Wednesday, Mar 22, 2023 - - - -



- - - - Thursday, Mar 23, 2023 - - - -



- - - - Friday, Mar 24, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday March 24, 2:00pm-3:30pm, Room 6417
Victoria Gitman CUNY

Parameter-free comprehension in second-order arithmetic

Second-order arithmetic has two types of objects: numbers and sets of numbers, which we think of as the reals. The second-order arithmetic framework has been used successfully to investigate what kinds of real numbers need to exist to prove various significant results in analysis. One of the strongest second-order arithmetic axiomatizations is the theory  consisting of the axioms  (for numbers), the set induction axiom, and comprehension for all second-order formulas with set parameters. How significant is the inclusion of set parameters in the comprehension scheme? Let  be like , but where set parameters are not allowed in the comprehension scheme. Harvey Friedman showed that  and  are equiconsistent because parameter-free comprehension suffices to build a model's version of the constructible universe  inside the model and the 'constructible' reals satisfy . Kanovei recently showed that models of  can be very badly behaved, for example, their sets may not even be closed under complement. Kanovei also showed that there can be nicely behaved models of  in which -comprehension (with set parameters) holds. He constructed his model in a forcing extension by a tree iteration of Sacks forcing. In Kanovei's model, -comprehension (with set parameters) fails and he asked whether this can be improved to -comprehension. In this talk, I will show how to construct a model of -comprehension and  in which -comprehension fails. The model will be constructed in a forcing extension by a tree iteration of Jensen's forcing. Jensen's forcing is a sub-poset of Sacks forcing constructed by Jensen to show that it is consistent to have a non-constructible -definable singleton real (every -definable set of reals is constructible by Shoenfield's Absoluteness).




Next Week in Logic at CUNY:

- - - - Monday, Mar 27, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 27, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Gregory Taylor (CUNY)
Title: First-order logics over fixed domain

Abstract: What we call first-order logic over fixed domain was initiated, in a certain guise, by Peirce around 1885 and championed, albeit in idiosyncratic form, by Zermelo in papers from the 1930s.  We characterize such logics model- and proof-theoretically and argue that they constitute exploration of a clearly circumscribed conception of domain-dependent generality.  Whereas a logic, or family of such, can be of interest for any of a variety of reasons, we suggest that one of those reasons might be that said logic fosters some clarification regarding just what qualifies as a logical concept, a logical operation, or a logical law.



- - - - Tuesday, Mar 28, 2023 - - - -



- - - - Wednesday, Mar 29, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:     Jim Otto.

Date and Time:     Wednesday March 29, 2023, 7:00 - 8:30 PM. ZOOM TALK

Title:     P Time, A Bounded Numeric Arrow Category, and Entailments.


Abstract: We revisit the characterization of the P Time functions from our McGill thesis.

1. We build on work of L. Roman (89) on primitive recursion and of A. Cobham (65) and Bellantoni-Cook(92) on P Time.

2. We use base 2 numbers with the digits 1 & 2. Let N be the set of these numbers. We split the tapes of a multi-tape Turing machine each into 2 stacks of digits 1 & 2. These are (modulo allowing an odd numberof stacks) the multi-stack machines we use to study P Time.

3. Let Num be the category with objects the finite products of N and arrows the functions between these. From its arrow category Num^2 we abstract the doctrine (here a category of small categories with chosen structure) PTime of categories with with finite products, base 2 numbers, 2-comprehensions, flat recursion, & safe recursion. Since PTime is a locally finitely presentable category, it has an initial category I. Our characterization is that the bottom of the image of I in Num^2 consists of the P Time functions.

4. We can use I (thinking of its arrows as programs) to run multi-stack machines long enough to get P Time.This is the completeness of the characterization.

5. We cut down the numeric arrow category Num^2, using Bellantoni-Cook growth & time bounds on the functions, to get a bounded numeric arrow category B. B is in the doctrine PTime. This yields the soundness of the characterization.

6. For example, the doctrine of toposes with base 1 numbers, choice, & precisely 2 truth values (which captures much of ZC set theory) likely lacks an initial category, much as there is an initial ring, but no initial field.

7. On the other hand, the L. Roman doctrine PR of categories with finite products, base 1 numbers, & recursion (that is, product stable natural numbers objects) does have an initial category as it consists of the strong models of a finite set of entailments. And is thus locally finitely presentable. We sketch the signature graph for these entailments. And some of these entailments. Similarly (but with more complexity) there are entaiments for the doctrine PTime.





- - - - Thursday, Mar 30, 2023 - - - -



- - - - Friday, Mar 31, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 31, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.

Benjamin Goodman, CUNY
-correct forcing axioms

The standard method of producing a model of a forcing axiom from a supercompact cardinal in fact gives a model of an even stronger principle: that for every small name a and every  formula  such that  is forceable by and preserved under further forcing in our forcing class, there is a filter  which meets a desired collection of dense sets and also interprets a such that  already holds. I will show how to generalize this result to formulas of higher complexity by starting with slightly stronger large cardinal assumptions, then discuss the bounded versions of these enhanced forcing axioms, their relationships to other similar principles, and their consequences.




Logic Workshop
CUNY Graduate Center
Friday March 31, 2:00pm-3:30pm, Room 6417
Corey Switzer, University of Vienna




- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 22nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Uhrik -- Hajnal--Máté Graphs and Cohen Reals We will study Hajnal--Máté (HM) graphs. The first construction of an HM graph was from the diamond+ principle. Since then several other constructions were provided with additional interesting properties, e.g. having no triangles. We will survey results about this class of graphs and provide a construction of a triangle free HM graph in a model after adding a single Cohen real. Time permitting we will introduce a generalization, so-called 𝛿-Hajnal--Máté graphs, and prove some of their basic properties and deduce a weak partition relation on ω_2. Best, David

(KGRC) Set Theory Seminar talk and Geometry and Analysis on Groups Seminar talk

Kurt Godel Research Center
The KGRC welcomes as guests: Martin Hils (host: Matthias Aschenbrenner) visits the KGRC until March 31. Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Lou van den Dries (host: Matthias Aschenbrenner) visits the KGRC from March 10 to March 22. Chieu-Minh Tran (host: Matthias Aschenbrenner) visits the KGRC from March 19 to March 22 and gives a talk on March 21, see below. Franz-Viktor Kuhlmann (host: Matthias Aschenbrenner) visits the KGRC from March 27 to March 31. José Nicolás Nájar Salinas (host: Miguel Moreno) visits the KGRC and gives a talk on March 29, details to be announced at a later time. Sergei Starchenko (host: Matthias Aschenbrenner) visits the KGRC from April 16 to April 30 and gives a talk, details to be announced at a later time. Zoltán Vidnyánszky (host: Vera Fischer) visits the KGRC on April 20 and gives a talk, details to be announced at a later time. Jaroslav Šupina (host: Vera Fischer) visits the KGRC from June 18 to June 24 and gives a talk, details to be announced at a later time. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, March 21 "Generalised Descriptive Set Theory, part II" Miguel Moreno (KGRC) We have introduced the notions of K-Borel class, K-analytic class, K-analytic-coanalytic class, K-Borel* class in the previous talk. In descriptive set theory the Borel class, the analytic-coanalytic class, and the Borel* class are the same class, we showed that this doesn't hold in the generalized descriptive set theory. In this talk, we will show the consistency of "K-Borel* class is equal to the K-analytic class". This was initially proved by Hyttinen and Weinstein (former Kulikov), under the assumption V=L. We will show a different proof that shows that this holds in L but also can be forced by a cofinality-preserving GCH-preserving forcing from a model of GCH, but also by a 3.99 \mu(A)$. We also show a more general result for the product of two sets, which can be seen as a Brunn-Minkowski-type inequality for sets with small measure in $\mathrm{SO}(3,\mathbb{R})$. (Joint with Yifan Jing and Ruixiang Zhang) Time and Place Talk at 3:00pm Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 9th floor room BZ 9 Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at.

Logic Seminar today in person in S17#05-11

NUS Logic Seminar
Hello, here just a reminder for the talk of Liu Shixiao in the logic seminar today at 17:00 hrs (now) on Forcing with Density Requirements. The abstract is: In the first half of the talk I shall be proving the Properness of Mathias forcing with lower density requirements. In the second half of the talk I shall demonstrate the difficulty in applying this method (and some other commonly used methods) to Silver forcing with lower density requirement. The location is S17#05-11 in the Department of Mathematics, NUS. Best regards, Frank

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the morning.

Our speaker this week will be Konstantin Slutsky from Iowa State University. This talk is going to take place this Friday, Mar. 17,  from 9am to 10am(UTC+8, Beijing time). 

Title: Partial actions and orbit equivalence relations

Abstract: In this talk, we will discuss the framework of partial actions for constructing orbit equivalent actions of Polish groups. While related ideas have been employed in ergodic theory and Borel dynamics for many years, the particular viewpoint of partial actions simplifies construction of orbit equivalent actions of distinct groups.  
As an application, we will present a Borel version of Katok's representation theorem for multidimensional Borel flows. One-dimensional flows are closely connected to actions of $\mathbb{Z}$ via the so-called "flow under a function" construction.  This appealing geometric picture does not generalize to higher dimensions.  Within the ergodic theoretical framework, Katok introduced the concept of a special flow as a way to connect multidimensional $\mathbb{R}^d$ and $\mathh{Z}^d$ actions.  We will show that similar connections continue to hold in Borel dynamics.
Another illustration of the partial actions techniques that we intend to touch is the following result: a Borel equivalence relation generated by a free $\mathbb{R}$-flow can also be generated by a free action of any non-discrete and non-compact Polish group. This is in contrast with the situation for discrete groups, where amenability distinguishes groups that can and cannot generate free finite measure-preserving hyperfinite actions.

___________________________________________________________________________________________________________________________________________________


This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title:                The 20th Nankai Logic Colloquium --Konstantin Slutsky

Time:                9:00am, Mar. 17, 2023 (Beijing Time)

Zoom Number:811 5076 2263

Passcode:         201148

Link:                https://zoom.us/j/81150762263?pwd=UmdvRkVEUjI2MHlONHQrdmQrRFJyZz09

_____________________________________________________________________


Best wishes,

Ming Xiao




Charla de Cesar Corral en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

Marzo 16

4:00 p.m. - 5:00 p.m. (Hora de Colombia)  

 

Familias MAD Fin-intersecting
Cesar Corral

Universidad de York

 

Abstract. Diremos que una familia MAD es pseudocompacta, si el hiperespacio de su \Psi-espacio lo es. Algunos resultados de Ginsgurg establecen relaciones entre propiedades del tipo compacidad de un espacio y su hiperespacio, además de que también preguntó la relación entre la pseudocompacidad de X^\omega y la de su hiperespacio exp(X).

Más tarde, Hrusak, Hernández y Martinez-Ruiz mostraron que existe un subespacio X de \beta(\omega) tal que X^\omega es pseudocompacto pero exp(X) no lo es. En el mismo trabajo, demostraron que, consistentemente, toda familia MAD es pseudocompacta, pero contrastantemente, también mostraron la consistencia de que hay una MAD no pseudocompacta. La existencia de familias MAD pseudocompactas en \textsf{ZFC} es aún desconocida. 
Para atacar este problema, introduciremos las familias MAD Fin-intersecting, mostraremos que estas familias son pseudocompactas y mostraremos su existencia en diferentes modelos, incluyendo algunos en los cuales la existencia de familias MAD pseudocompactas era aún desconocido.

Este es un trabajo conjunto con Vinicius de Oliveira Rodrigues.


Zoom meeting information.
Meeting ID: 856 1882 0721
Passcode: 123456

Cross-Alps Logic Seminar (speaker: Victor Selivanov)

Cross-Alps Logic Seminar
On Friday 17.03.2023 at 16.00
Victor Selivanov (Institute of Informatics Systems, Novosibirsk)
will give a talk on 
Boole vs Wadge: Comparing Basic Tools of Descriptive Set Theory

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Vincenzo

CosmoCaixa Barcelona: Joel Hamkins: pensament estratègic en jocs infinits

Barcelona Logic Seminar
Dear All,
Just a reminder that you may get a 3 Euros admission fee for the Cosmocaixa museum, on the occasion of Joel hamkins’ talk. Go to the link below to get the entrance ticket and use the following code:

CCX23UNIVERSITAT 

I strongly encourage you to attend Joel’s talk, and visit the Cosmocaixa!
See you there!
Joan


Benvolguts,
us envio l’anunci de la conferència que farà Joel Hamkins al Cosmocaixa el dia 16 de març a les 7. L’entrada val 6 Euros, però us puc donar un codi que la redueix a 3. Inclou la visita al Cosmocaixa.

Joel Hamkins: pensament estratègic en jocs infinits 

https://cosmocaixa.org/ca/p/pensament-estrategic-en-jocs-infinits_a122155152 . 

Espero que vingueu,
Joan


Dear All,
here is the announcement of the talk by Joel Hamkins he will give at Cosmocaixa (Science Museum in Barcelona) on March 16, 7pm. The entry fee is 6 Euros, but I can give you a code that reduces it to 3 Euros. It includes the entrance to the museum
  
Joel Hamkins: Strategic Thinking in Infinite Games

https://cosmocaixa.org/ca/p/pensament-estrategic-en-jocs-infinits_a122155152 . 

Hope to see you there!
Joan


neal
Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 15th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There is no fixed program yet. Participants are encouraged to bring their topics and questions to share. (Chris is leaving for couple of months at the end of the week, so this will be for some time the last opportunity to ask him something. ;-) Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 13, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 13, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Melvin Fitting (CUNY)
Title: On Kripke’s proof of Kripke completeness

Abstract: Saul Kripke announced his possible world semantics in 1959, and `published his proof of axiomatic completeness for the standard modal logics of the time in 1963.  It is very unlike the standard completeness proof used today, which involves a Lindenbaum/Henkin construction and produces canonical models.  Kripke’s proof involved tableaus, in a format that is difficult to follow, and uses tableau construction algorithms that are complex and somewhat error prone to describe. I will first discuss Kripke’s proof, then the historical origins of the modern version.  Then I will show that completeness, proved Kripke style, could actually have been done in the Lindenbaum/Henkin way, thus simplifying things considerably.  None of this is new but, with the parts collected together it is an interesting story. “In my end is my beginning”.


- - - - Tuesday, Mar 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, March 14, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Bartosz Wcisło, University of Gdańsk
Satisfaction classes with the full collection scheme

Satisfaction classes are subsets of models of Peano arithmetic which satisfy Tarski's compositional clauses. Alternatively, we can view satisfaction or truth classes as the extension of a fresh predicate T(x) (the theory in which compositional clauses are viewed as axioms is called CT^-).

It is easy to see that CT^- extended with a full induction scheme is not conservative over PA, since it can prove, for instance, the uniform reflection over arithmetic. By a nontrivial argument of Kotlarski, Krajewski, and Lachlan, the sole compositional axioms of CT^- in fact form a conservative extension of PA. Moreover, in order to obtain non-conservativity it is enough to add induction axioms for the Delta_0 formulae containing the truth predicate.

Answering a question of Kaye, we will show that the theory of compositional truth, CT^- with the full collection scheme is a conservative extension of Peano Arithmetic. Following the initial suggestion of Kaye, we will in fact show that any countable recursively saturated model M of PA has an elementary omega_1-like end extension M' such that M' carries a full satisfaction class.





- - - - Wednesday, Mar 15, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Jens Hemelaer, University of Antwerp.
Date and Time:     Wednesday March 15, 2023, 7:00 - 8:30 PM. IN PERSON TALK.
Title:     EILC toposes.

Abstract: In topos theory, local connectedness of a geometric morphism is a very geometric property, in the sense that it is stable under base change, can be checked locally, and so on. In some situations however, the weaker property of being essential is easier to verify. In this talk, we will discuss EILC toposes: toposes E such that any essential geometric morphism with codomain E is automatically locally connected. It turns out that many toposes of interest are EILC, including toposes of sheaves on Hausdorff spaces and classifying toposes of compact groups.



- - - - Thursday, Mar 16, 2023 - - - -



- - - - Friday, Mar 17, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 17, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.

Jonathan Osinski, University of Hamburg
Model-Theoretic Characterizations of Weak Vopěnka's Principle

It has been known since the 1980s that Vopěnka's Principle (VP) is equivalent to certain statements about logics, e.g. to the schema 'Every logic has a compactness cardinal.' On the other hand, it was only recently shown by Trevor Wilson that a related statement statement called Weak Vopěnka's Principle (WVP) is strictly weaker than VP. In fact, Joan Bagaria and Wilson showed that WVP is equivalent to the existence of -strong cardinals for all natural numbers . We generalize logical characterizations of strong cardinals to achieve a characterization of -strong cardinals and therefore of WVP in terms of properties of strong logics. This is partly joint work with Will Boney and partly with Trevor Wilson.




Logic Workshop
CUNY Graduate Center
Friday March 17, 2:00pm-3:30pm, Room 6417

Filippo Calderoni, Rutgers University
Rotation equivalence and rigidity

The theory of countable Borel equivalence relations analyzes the actions of countable groups on Polish spaces. The main question studied is how much information is encoded by the corresponding orbit space. The amount of encoded information reflects the extent to which the action is rigid.

In this talk we will discuss rigidity results for the action of the group of rational rotations. In particular we will analyze the rotation equivalence on spheres in higher dimension. This is connected to superrigidity results of Margulis and to Zimmer’s program about the actions of discrete subgroups of Lie groups on manifolds.



Next Week in Logic at CUNY:

- - - - Monday, Mar 20, 2023 - - - -

Rutgers Logic Seminar 
Monday, March 20, 2pm, Rutgers University, Hill 005
Roman Kossak, CUNY
Absolute Undefinability



Logic and Metaphysics Workshop
Date: Monday, March 20, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Gregory Taylor (CUNY)
Title: First-order logics over fixed domain

Abstract: What we call first-order logic over fixed domain was initiated, in a certain guise, by Peirce around 1885 and championed, albeit in idiosyncratic form, by Zermelo in papers from the 1930s.  We characterize such logics model- and proof-theoretically and argue that they constitute exploration of a clearly circumscribed conception of domain-dependent generality.  Whereas a logic, or family of such, can be of interest for any of a variety of reasons, we suggest that one of those reasons might be that said logic fosters some clarification regarding just what qualifies as a logical concept, a logical operation, or a logical law.



- - - - Tuesday, Mar 21, 2023 - - - -



- - - - Wednesday, Mar 22, 2023 - - - -



- - - - Thursday, Mar 23, 2023 - - - -



- - - - Friday, Mar 24, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Friday March 24, 2:00pm-3:30pm, Room 6417
Victoria Gitman CUNY



- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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(KGRC) talks on Tuesday, March 14 and Thursday, March 16

Kurt Godel Research Center
The KGRC welcomes as guests: Martin Hils (host: Matthias Aschenbrenner) visits the KGRC until March 31. Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Lou van den Dries (host: Matthias Aschenbrenner) visits the KGRC from March 10 to March 22. Silvain Rideau-Kikuchi (host: Matthias Aschenbrenner) visits the KGRC from March 15 to March 20 and gives a talk, see below. José Nicolás Nájar Salinas (host: Miguel Moreno) visits the KGRC and gives a talk on March 29, details to be announced at a later time. Sergei Starchenko (host: Matthias Aschenbrenner) visits the KGRC from April 16 to April 30 and gives a talk, details to be announced at a later time. * * * For a video recording of Juris Steprāns's talk, please use https://univienna.zoom.us/rec/share/_U6vJ6rbIaT1WaoflIav52OiR4GsAQ-W3Aw00aD4jb08xvlf7C4QoQJyD_KlQkEc.h7MOui67bVxLr9Cl and passcode jTi%8uqf * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, March 14 "Generalised Descriptive Set Theory, part I" Miguel Moreno (KGRC) This is the first of three talks about Generalised Descriptive Set Theory. The aim of this talk is to introduce the notions of K‑Borel class, K‑analytic class, K‑analytic-coanalytic class, K‑Borel* class, and show the relation between these classes. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Students at Uni Wien are required to attend in person.) Please direct any other questions about this talk to vera.fischer@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, March 16 "Multi topological fields, approximations and NTP2" Silvain Rideau-Kikuchi (U Paris Diderot, FR) (Joint work with S. Montenegro) The striking resemblance between the behaviour of pseudo-algebraically closed, pseudo real closed and pseudo p-adically fields has lead to numerous attempts at describing their properties in a unified manner. In this talk I will present another of these attempts: the class of pseudo-T-closed fields, where T is an enriched theory of fields. These fields verify a « local-global » principle with respect to models of T for the existence of points on varieties. Although it very much resembles previous such attempts, our approach is more model theoretic in flavour, both in its presentation and in the results we aim for. The first result I would like to present is an approximation result, generalising a result of Kollar on PAC fields, respectively Johnson on henselian fields. This result can be rephrased as the fact that existential closeness in certain topological enrichments come for free from existential closeness as a field. The second result is a (model theoretic) classification result for bounded pseudo-T-closed fields, in the guise of the computation of their burden. One of the striking consequence of these two results is that a bounded perfect PAC field with n independent valuations has burden n and, in particular, is NTP2. Time and Place Talk at 3:00pm in hybrid mode: on-site as well as via Zoom Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Students at Uni Wien are required to attend in person.) Please direct any other questions about this talk to matthias.aschenbrenner@univie.ac.at.

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the afternoon.


Our speaker this week will be Vladimir Kanovei from the Institute for Information Transmission Problems, RAS. This talk is going to take place this Friday, Mar.10, from 4pm to 5pm(UTC+8, Beijing time). 


Title:
On the significance of parameters in the choice and сomprehension schemata in the 2nd-order Peano arithmetic Abstract Parameters are free variables in various axiom schemata in PA, ZFC, and other similar theories. Given an axiom schema S, we let S* be the parameter-free sub-schema. Kreisel (A survey of proof theory, JSL 1968) was one of those who paid attention to the comparison of some schemata in second-order PA and their parameter-free versions. In particular, Kreisel noted that [...] if one is convinced of the significance of something like agiven axiom schema, it is natural to study details, such as the effect of parameters. This talk is devoted to the effect of parameters in the schemata of Comprehension and Choice in second-order arithmetic.
___________________________________________________________________________________________________________________________________________________


This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title:                The 19th Nankai Logic Colloquium --Vladimir Kanovei
Time:                16:00pm, Mar. 10, 2023 (Beijing Time)
Zoom Number:844 4116 3813
Passcode:         628524
Link:                 https://zoom.us/j/84441163813?pwd=WFlSbThMbldUeVZYZncrTGVyYmp5QT09


_____________________________________________________________________


Best wishes,

Ming Xiao




UPDATE - This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

A quick update - Unfortunately, Dr. Weinert will be unable to speak on March 10, so the Logic Workshop is canceled this week.

Best,
Jonas



This Week in Logic at CUNY:

- - - - Monday, Mar 6, 2023 - - - -

Rutgers Logic Seminar 
Monday, March 6, 2pm, Rutgers University, Hill 005
Will Adkisson, UIC
The Strong and Super Tree Property

Logic and Metaphysics Workshop
Date: Monday, March 6, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Gary Ostertag (CUNY/Mount Sinai)

Title: Lewis on accommodation and representation de re

Abstract: Recall Lumpl, the lump of clay out of which the statue Goliath is fashioned. While (1) ‘Lumpl could have survived a squashing’ is true, (2) ‘Goliath could have survived a squashing’ is false, it being after all essential to Goliath, but not to Lumpl, that it be a statue. We have here an example of what David Lewis (1986) called “the inconstancy of representation de re”. For Lewis, the inconstancy does not amount to inconsistency, but rather points to the context-sensitivity of de re modal predication: (1) and (2) make implicit, context-sensitive reference to different counterpart relations. Once we recognize this, Lewisians argue, it becomes clear how our intuitive truth-conditional judgments are fully consistent. As I show, however, the conversational rule that triggers the implicit reference not only fails to license the reference shift, it effectively prohibits it. The upshot is that counterpart theory is deprived of a central motivation.

 



- - - - Tuesday, Mar 7, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, March 7, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Bellaouar Djamel, University 08 Mai 1945 Guelma
Some generalizations on the representation of unlimited natural numbers

Based on permanence principles of nonstandard analysis and as a continuation of the papers [1-3], we present some notes and questions on the representation of unlimited natural numbers. As a natural generalization, let  be an unlimited  by  matrix with integer entries (i.e one of its integer entries is unlimited). Here we prove that every unlimited matrix  with integer entries can be written as the sum of a limited matrix S with integer entries and the product of two unlimited matrices  and  with integer entries, that is, . For further research, we propose several matrix representation forms.

Finally, we consider the numbers of the form  where , are integers, which are called Gaussian integers. In the case when  or  is unlimited, the number  is said to be unlimited. Also, some notes on the representation of unlimited Gaussian integers are given.

[1] A. Boudaoud, La conjecture de Dickson et classes particulière d'entiers, Ann. Math. Blaise Pascal. 13 (2006), 103-109.
[2] A. Boudaoud and D. Bellaouar, Representation of integers: A nonclassical point of view, J. Log. Anal. 12:4 (2020) 1-31.
[3] K. Hrbacek, On Factoring of unlimited integers, J. Log. Anal. 12:5 (2020) 1-6.




- - - - Wednesday, Mar 8, 2023 - - - -



- - - - Thursday, Mar 9, 2023 - - - -



- - - - Friday, Mar 10, 2023 - - - -

Logic Workshop - TODAY'S WORKSHOP IS CANCELLED
CUNY Graduate Center
Friday March 10, 2:00pm-3:30pm, Room 6417



Set Theory Seminar
CUNY Graduate Center
Friday, March 10, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
James Holland, Rutgers University



Next Week in Logic at CUNY:

- - - - Monday, Mar 13, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 13, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Melvin Fitting (CUNY)
Title: On Kripke’s proof of Kripke completeness

Abstract: Saul Kripke announced his possible world semantics in 1959, and `published his proof of axiomatic completeness for the standard modal logics of the time in 1963.  It is very unlike the standard completeness proof used today, which involves a Lindenbaum/Henkin construction and produces canonical models.  Kripke’s proof involved tableaus, in a format that is difficult to follow, and uses tableau construction algorithms that are complex and somewhat error prone to describe. I will first discuss Kripke’s proof, then the historical origins of the modern version.  Then I will show that completeness, proved Kripke style, could actually have been done in the Lindenbaum/Henkin way, thus simplifying things considerably.  None of this is new but, with the parts collected together it is an interesting story. “In my end is my beginning”.


- - - - Tuesday, Mar 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, March 14, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Bartosz Wcisło, University of Gdańsk




- - - - Wednesday, Mar 15, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Jens Hemelaer, University of Antwerp.
Date and Time:     Wednesday March 15, 2023, 7:00 - 8:30 PM. IN PERSON TALK.
Title:     EILC toposes.

Abstract: In topos theory, local connectedness of a geometric morphism is a very geometric property, in the sense that it is stable under base change, can be checked locally, and so on. In some situations however, the weaker property of being essential is easier to verify. In this talk, we will discuss EILC toposes: toposes E such that any essential geometric morphism with codomain E is automatically locally connected. It turns out that many toposes of interest are EILC, including toposes of sheaves on Hausdorff spaces and classifying toposes of compact groups.



- - - - Thursday, Mar 16, 2023 - - - -



- - - - Friday, Mar 17, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 17, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Jonathan Osinski, University of Hamburg


Logic Workshop
CUNY Graduate Center
Modality TBA
Friday March 17, 2:00pm-3:30pm, Room 6417
Filippo Calderoni, Rutgers University


- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Charla de Paul Szeptycki en el Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

Seminario Colombo Mexicano de Teoría de Conjuntos

 

March 9

4:00 p.m. - 5:00 p.m. (Colombia time)  

 

A Ramsey-theoretic strengthening of sequential compactness
Paul Szeptycki

York University

 

Abstract. We define a topological space $X$ to be $n$-Ramsey if for every map $f: [\omega]^n \rightarrow X$ there is an infinite set $M$ and a point $x \in X$ such that $f \uphaproonright [M]^n$ converges to $x$ in a natural sense. Sequentially compact spaces are precisely the $1$-Ramsey spaces and any $n+1$-Ramsey space is $n$-Ramsey.  We discuss basic results about these new classes of spaces, directions of current work in progress and some open problems.  



Zoom meeting information.
Meeting ID: 856 1882 0721
Passcode: 123456


This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 6, 2023 - - - -

Rutgers Logic Seminar 
Monday, March 6, 2pm, Rutgers University, Hill 005
Will Adkisson, UIC
The Strong and Super Tree Property

Logic and Metaphysics Workshop
Date: Monday, March 6, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Gary Ostertag (CUNY/Mount Sinai)

Title: Lewis on accommodation and representation de re

Abstract: Recall Lumpl, the lump of clay out of which the statue Goliath is fashioned. While (1) ‘Lumpl could have survived a squashing’ is true, (2) ‘Goliath could have survived a squashing’ is false, it being after all essential to Goliath, but not to Lumpl, that it be a statue. We have here an example of what David Lewis (1986) called “the inconstancy of representation de re”. For Lewis, the inconstancy does not amount to inconsistency, but rather points to the context-sensitivity of de re modal predication: (1) and (2) make implicit, context-sensitive reference to different counterpart relations. Once we recognize this, Lewisians argue, it becomes clear how our intuitive truth-conditional judgments are fully consistent. As I show, however, the conversational rule that triggers the implicit reference not only fails to license the reference shift, it effectively prohibits it. The upshot is that counterpart theory is deprived of a central motivation.

 



- - - - Tuesday, Mar 7, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, March 7, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Bellaouar Djamel, University 08 Mai 1945 Guelma
Some generalizations on the representation of unlimited natural numbers

Based on permanence principles of nonstandard analysis and as a continuation of the papers [1-3], we present some notes and questions on the representation of unlimited natural numbers. As a natural generalization, let  be an unlimited  by  matrix with integer entries (i.e one of its integer entries is unlimited). Here we prove that every unlimited matrix  with integer entries can be written as the sum of a limited matrix S with integer entries and the product of two unlimited matrices  and  with integer entries, that is, . For further research, we propose several matrix representation forms.

Finally, we consider the numbers of the form  where , are integers, which are called Gaussian integers. In the case when  or  is unlimited, the number  is said to be unlimited. Also, some notes on the representation of unlimited Gaussian integers are given.

[1] A. Boudaoud, La conjecture de Dickson et classes particulière d'entiers, Ann. Math. Blaise Pascal. 13 (2006), 103-109.
[2] A. Boudaoud and D. Bellaouar, Representation of integers: A nonclassical point of view, J. Log. Anal. 12:4 (2020) 1-31.
[3] K. Hrbacek, On Factoring of unlimited integers, J. Log. Anal. 12:5 (2020) 1-6.




- - - - Wednesday, Mar 8, 2023 - - - -



- - - - Thursday, Mar 9, 2023 - - - -



- - - - Friday, Mar 10, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Modality TBA
Friday March 10, 2:00pm-3:30pm, Room 6417
Thilo Weinert, University of Vienna


Set Theory Seminar
CUNY Graduate Center
Friday, March 10, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
James Holland, Rutgers University



Next Week in Logic at CUNY:

- - - - Monday, Mar 13, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 13, 4.15-6.15pm (NY time), GC 9206
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/

Melvin Fitting (CUNY)
Title: On Kripke’s proof of Kripke completeness

Abstract: Saul Kripke announced his possible world semantics in 1959, and `published his proof of axiomatic completeness for the standard modal logics of the time in 1963.  It is very unlike the standard completeness proof used today, which involves a Lindenbaum/Henkin construction and produces canonical models.  Kripke’s proof involved tableaus, in a format that is difficult to follow, and uses tableau construction algorithms that are complex and somewhat error prone to describe. I will first discuss Kripke’s proof, then the historical origins of the modern version.  Then I will show that completeness, proved Kripke style, could actually have been done in the Lindenbaum/Henkin way, thus simplifying things considerably.  None of this is new but, with the parts collected together it is an interesting story. “In my end is my beginning”.


- - - - Tuesday, Mar 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, March 14, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)
Bartosz Wcisło, University of Gdańsk




- - - - Wednesday, Mar 15, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Jens Hemelaer, University of Antwerp.
Date and Time:     Wednesday March 15, 2023, 7:00 - 8:30 PM. IN PERSON TALK.
Title:     EILC toposes.

Abstract: In topos theory, local connectedness of a geometric morphism is a very geometric property, in the sense that it is stable under base change, can be checked locally, and so on. In some situations however, the weaker property of being essential is easier to verify. In this talk, we will discuss EILC toposes: toposes E such that any essential geometric morphism with codomain E is automatically locally connected. It turns out that many toposes of interest are EILC, including toposes of sheaves on Hausdorff spaces and classifying toposes of compact groups.



- - - - Thursday, Mar 16, 2023 - - - -



- - - - Friday, Mar 17, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 17, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Jonathan Osinski, University of Hamburg


Logic Workshop
CUNY Graduate Center
Modality TBA
Friday March 17, 2:00pm-3:30pm, Room 6417
Filippo Calderoni, Rutgers University


- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 
Please find attached the announcement of the next Barcelona Set Theory Seminar session.

SPEAKER: Radek Honzik
TITLE: Compactness principles at small cardinals and their preservation
DATE: Wednesday, 8 March 2023
TIME: 16:00 (CET)
PLACE: Room B1 (UB). The Seminar can also be followed online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 8th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Topics in cardinal arithmetic We will discuss some recent results and some not-so-recent results in cardinal arithmetic and PCF theory. The precise topics will depend on the interests of the audience and the preparedness of the speaker but may include: existence theorems about PCF-theoretic scales, Silver's theorem for pseudopowers, the cov vs. pp problem, or recent work of the speaker showing that a generalized narrow system property implies Shelah's Strong Hypothesis. Best, David

(KGRC) two talks at U Wien and TU Wien

Kurt Godel Research Center
The KGRC welcomes as guests: Martin Hils (host: Matthias Aschenbrenner) visits the KGRC until March 31. Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Juris Steprāns (host: Vera Fischer) visits the KGRC from March 6 to March 10 and gives a talk, see below. Lou van den Dries (host: Matthias Aschenbrenner) visits the KGRC from March 10 to March 22. Silvain Rideau-Kikuchi (host: Matthias Aschenbrenner) visits the KGRC from March 15 to March 20 and gives a talk, details to be announced at a later time. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, March 7 "Selective and Milliken-Taylor ultrafilters" Juris Steprāns (York U, CA) I will report on joint work with Dilip Raghavan solving a question of Blass about whether the existence of many selective ultrafilters implies the existence of Milliken-Taylor ultrafilters. The first part of the talk will provide the historical context of what was known in the mid 80s that prompted Blass to ask his question. The second part will discuss the key technical advance in our argument. Time and Place Talk at 3:00pm Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * FG1 Seminar Algebra Research Unit Wednesday, March 8 "Various ways to compare spaces, subsets, and functions" Raphaël Carroy (Università degli Studi di Torino, IT) One can consider a quasi-order like topological embeddability when one wants to compare a Polish (or analytic) space to another. If instead one tries to rank the complexities emerging among subsets of a given space, continuous reducibility becomes relevant. Both these quasi-orders have extensions to functions between Polish (or analytic) spaces. Some natural questions about these quasi-orders are then: the existence of simple bases, characterizing the simplicity or complexity of the quasi-order in itself, and describing it when it turns out to be simple enough. I will try to give some context on these quasi-orders and review known and more recent results and applications. Times and Places Snacks and beverages at 2:00pm Institute of Discrete Mathematics and Geometry TU Wien Wiedner Hauptstrasse 8-10 1040 Wien Austria 5th floor, green part room Besprechungsraum DA 05 C22 Talk at 2:45pm Institute of Discrete Mathematics and Geometry TU Wien Wiedner Hauptstrasse 8-10 1040 Wien Austria 8th floor, green part room Dissertantenraum DA 08 B19 Please direct any questions about this talk to sandra.mueller@tuwien.ac.at.

CosmoCaixa Barcelona: Joel Hamkins: pensament estratègic en jocs infinits

Barcelona Logic Seminar
Benvolguts,
us envio l’anunci de la conferència que farà Joel Hamkins al Cosmocaixa el dia 16 de març a les 7. L’entrada val 6 Euros, però us puc donar un codi que la redueix a 3. Inclou la visita al Cosmocaixa.

Joel Hamkins: pensament estratègic en jocs infinits 

https://cosmocaixa.org/ca/p/pensament-estrategic-en-jocs-infinits_a122155152 . 

Espero que vingueu,
Joan


Dear All,
here is the announcement of the talk by Joel Hamkins he will give at Cosmocaixa (Science Museum in Barcelona) on March 16, 7pm. The entry fee is 6 Euros, but I can give you a code that reduces it to 3 Euros. It includes the entrance to the museum
  
Joel Hamkins: Strategic Thinking in Infinite Games

https://cosmocaixa.org/ca/p/pensament-estrategic-en-jocs-infinits_a122155152 . 

Hope to see you there!
Joan



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Logic Seminar 8 March 2023 17:00 hrs at NUS by Chong Chitat

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 8 March 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#05-11 Speaker: Chong Chitat, National University of Singapore Title: Proof-theoreitic strength of the Halpern-Lauchli Theorem URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Let T be the full infinite binary tree (i.e. the Cantor space). An infinite subtree S of T is a strong subtree if (i) S is isomorphic to T, (ii) if sigma is a node in S, and sigma_0, sigma_1 are its immediate successors in S, then sigma_0 and sigma_1 have the same length in T and furthermore (iii) the intersection of sigma_0 and sigma_1 is sigma. The Halpern-Lauchli Theorem is a theorem in combinatorial mathematics which states that for any finite number of infinite full binary trees T_1,T_2,..., T_d, and any finite coloring of the d-row vectors in T_1 x T_2 x ... x T_d, there exist strong subtrees S_1 subseteq T_1, S_2 subseteq T_2, ..., S_d subseteq T_d for which all d-row vectors in S_1 x S_2 x ... x S_d have the same color. This Ramsey type theorem is yet another striking demonstration of the existence of order within chaotic disorder. There is no known simple proof of this theorem in the published literature. In this talk we discuss the proof-theoretic strength of the Halpern-Lauchli theorem from the reverse mathematics point of view. In particular, we give a characterisation of the inductive strength of this theorem as well as its conservation strength over a base theory weaker than Sigma_2-induction. This is joint work with Li Wei and Yang Yue.

Today's Logic Seminar is via Zoom

NUS Logic Seminar
Hello, please note that today's talk is by Zoom and there is no physical meeting. Here again the login info: Return-Path: Date: Fri, 24 Feb 2023 15:00:41 +0800 From: Frank STEPHAN To: matyangy@nus.edu.sg, settheorytalks@gmail.com, belanger@nus.edu.sg, Subject: Logic Seminar 1 March 2023 17:00 hrs Singapore time by Linus Richter Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 1 March 2023, 17:00 hrs Place: NUS, Department of Mathematics, Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Linus Richter, Victoria University of Wellington Title: Co-analytic Counterexamples to Marstrand's Projection Theorem Abstract: A recent "point-to-set principle" of Jack Lutz and Neil Lutz characterises the Hausdorff dimension of any subset of Euclidean space in terms of the Kolmogorov complexity of its individual points. Sets with particular fractal properties can now be constructed point-by-point, by coding "enough" information into each point, bit-by-bit. After introducing the point-to-set principle, I will present a new result in fractal geometry: under V=L (the axiom of constructiblity), I will outline the construction of co-analytic sets of Euclidean space which fail Marstrand's Projection Theorem, a classical result in fractal geometry concerning the dimension of orthogonal projections of analytic plane sets onto lines. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the afternoon.


Our speaker this week will be Martino Lupini from the University of Bologna. This talk is going to take place this Friday, Mar. 03,  from 16:00 to 17:00 (UTC+8, Beijing time). 


Title: Definable refinements of classical algebraic invariants

Abstract: In this talk I will explain how methods from logic allow one to construct refinements of classical algebraic invariants that are endowed with additional topological and descriptive set-theoretic information. This approach brings to fruition initial insights due to Eilenberg, Mac Lane, and Moore (among others) with the additional ingredient of recent advanced tools from logic. I will then present applications of this viewpoint to invariants from a number of areas in mathematics, including operator algebras, group theory, algebraic topology, and homological algebra.

___________________________________________________________________________________________________________________________________________________


This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title:                The 18th Nankai Logic Colloquium --Martino Lupini

Time:                16:00, Mar. 3, 2023 (Beijing Time)

Zoom Number:859 1679 0296

Passcode:         577088

Link:                 https://zoom.us/j/85916790296?pwd=WGRrZjJKa0kvRE9KSGtxNkJia2JiUT09

_____________________________________________________________________


Best wishes,

Ming Xiao




Cross-Alps Logic Seminar (speaker: Dugald MacPherson)

Cross-Alps Logic Seminar
On Friday 03.03.2023 at 16.00
Dugald MacPherson (University of Leeds)
will give a talk on 
Uniform families of definable sets in finite structures

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Vincenzo

(KGRC) Logic Colloquium talk on Thursday, March 2

Kurt Godel Research Center
The KGRC welcomes as guests: Martin Hils (host: Matthias Aschenbrenner) visits the KGRC until March 31. Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Jerzy Kąkol (host: Damian Sobota) visits the KGRC until March 3. Manuel López Pellicer (host: Damian Sobota) visits the KGRC until March 3. Katrin Tent (host: Matthias Aschenbrenner) visits the KGRC from March 1 to March 5 and gives a talk (see below). Juris Steprāns (host: Vera Fischer) visits the KGRC from March 6 to March 10 and gives a talk, details to be announced at a later time. Silvain Rideau-Kikuchi (host: Matthias Aschenbrenner) visits the KGRC from March 15 to March 20 and gives a talk, details to be announced at a later time. * * * Logic Colloquium Kurt Gödel Research Center Thursday, March 2 "Simplicity of automorphism groups of homogeneous structures" Katrin Tent (Universität Münster, DE) We discuss some general criteria that can be used to show that the automorphism group of a homogeneous structure (such as metric space, right-angled building, graph or hypergraphs) are simple groups or have simple quotients. Time and Place Talk at 3:00pm Universität Wien Institut für Mathematik Oskar-Morgenstern-Platz 1 1090 Wien 2nd floor room HS 11 If you would like to follow the talk online, please let Matthias Aschenbrenner (matthias.aschenbrenner@univie.ac.at) or Vera Fischer (vera.fischer@univie.ac.at) know in advance and we will arrange for it to be streamed.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 1st at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet determined. If anybody is interested in speaking or to hear something specific, do let me know. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 27, 2023 - - - -

Rutgers Logic Seminar 
Monday, February 27, 2pm, Rutgers University, Hill 005
Leonardo Nagami Coregliano, IAS Princeton
Ramsey's Theorem in the countable and weak randomness


Logic and Metaphysics Workshop
Date: Monday, February 27, 4.15-6.15pm (NY time), GC 9205
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Lionel Shapiro, UConn
Title: Neopragmatism and logic: A deflationary proposal

Abstract: Neopragmatists seek to sidestep metaphysical puzzles by shifting the target of philosophical explanation from the objects we think and talk about to the functions of expressions and concepts in our cognitive economy. Logical vocabulary can serve as a target for neopragmatist inquiry, and it has also posed obstacles to neopragmatist accounts of other vocabulary. I will argue that the obstacles can be addressed by adopting a neopragmatist perspective toward logical relations, such as logical consequence, and toward propositional content. Doing so calls into question two purported constraints on explanations of the functions of logical connectives. I will sketch an account made possible by rejecting those constraints, one according to which logical connectives serve to express dialectical attitudes. The proposal is deflationary in two ways: it rests on an extension of deflationism from truth to logical relations, and it aims to deflate some of neopragmatists’ theoretical ambitions.

 


- - - - Tuesday, Feb 28, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 28, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Zuzana Hanikova, Czech Academy of Sciences
Vopěnka's Alternative Set Theory and its mathematical context

Vopěnka first presented his Alternative Set Theory (AST) in the monograph 'Mathematics in the Alternative Set Theory' published by Teubner, Leipzig in 1979. Another book presenting the theory, 'Introduction to Mathematics in the Alternative Set Theory', was published in 1989 in Slovak by Alfa, Bratislava. In addition there are numerous journal papers on the AST by members of the research group established by Vopěnka, and the proceedings of a conference dedicated to the AST, also from 1989. In several essays, Vopěnka sought to lay out the motivation and philosophical import of the AST and some of his subsequent work. As one consequence of the emphasis on his philosophy, the mathematical inspiration for the AST has been somewhat obliterated. The aim of the talk is to discuss the design choices Vopěnka made for the AST in relation to pertinent mathematical developments of the 20th century, such as Skolem's work on nonstandard models of arithmetic, Robinson's nonstandard analysis, Rieger's nonstandard models of arithmetic, Vopěnka's nonstandard model of set theory, Vopěnka and Hájek's theory of semisets, or Parikh's almost consistent theories. The presentation will include an outline of the AST following the works of Vopěnka and Sochor. This is a historical talk; no new mathematical results on the AST will be presented.




- - - - Wednesday, Mar 1, 2023 - - - -



- - - - Thursday, Mar 2, 2023 - - - -



- - - - Friday, Mar 3, 2023 - - - -




Next Week in Logic at CUNY:

- - - - Monday, Mar 6, 2023 - - - -

Rutgers Logic Seminar 
Monday, March 6, 2pm, Rutgers University, Hill 005
Will Adkisson, UIC


Logic and Metaphysics Workshop
Date: Monday, March 6, 4.15-6.15pm (NY time), GC 9205
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Gary Ostertag (CUNY/Mount Sinai)

Title: Lewis on accommodation and representation de re

Abstract: Recall Lumpl, the lump of clay out of which the statue Goliath is fashioned. While (1) ‘Lumpl could have survived a squashing’ is true, (2) ‘Goliath could have survived a squashing’ is false, it being after all essential to Goliath, but not to Lumpl, that it be a statue. We have here an example of what David Lewis (1986) called “the inconstancy of representation de re”. For Lewis, the inconstancy does not amount to inconsistency, but rather points to the context-sensitivity of de re modal predication: (1) and (2) make implicit, context-sensitive reference to different counterpart relations. Once we recognize this, Lewisians argue, it becomes clear how our intuitive truth-conditional judgments are fully consistent. As I show, however, the conversational rule that triggers the implicit reference not only fails to license the reference shift, it effectively prohibits it. The upshot is that counterpart theory is deprived of a central motivation.

 



- - - - Tuesday, Mar 7, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, March 7, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Bellaouar Djamel, University 08 Mai 1945 Guelma
Some generalizations on the representation of unlimited natural numbers

Based on permanence principles of nonstandard analysis and as a continuation of the papers [1-3], we present some notes and questions on the representation of unlimited natural numbers. As a natural generalization, let  be an unlimited  by  matrix with integer entries (i.e one of its integer entries is unlimited). Here we prove that every unlimited matrix  with integer entries can be written as the sum of a limited matrix S with integer entries and the product of two unlimited matrices  and  with integer entries, that is, . For further research, we propose several matrix representation forms.

Finally, we consider the numbers of the form  where , are integers, which are called Gaussian integers. In the case when  or  is unlimited, the number  is said to be unlimited. Also, some notes on the representation of unlimited Gaussian integers are given.

[1] A. Boudaoud, La conjecture de Dickson et classes particulière d'entiers, Ann. Math. Blaise Pascal. 13 (2006), 103-109.
[2] A. Boudaoud and D. Bellaouar, Representation of integers: A nonclassical point of view, J. Log. Anal. 12:4 (2020) 1-31.
[3] K. Hrbacek, On Factoring of unlimited integers, J. Log. Anal. 12:5 (2020) 1-6.




- - - - Wednesday, Mar 8, 2023 - - - -



- - - - Thursday, Mar 9, 2023 - - - -



- - - - Friday, Mar 10, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Modality TBA
Friday March 10, 2:00pm-3:30pm, Room 6417
Thilo Weinert, University of Vienna


Set Theory Seminar
CUNY Graduate Center
Friday, March 10, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
James Holland, Rutgers University



- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 
Please find attached the announcement of the next Barcelona Set Theory Seminar session.

SPEAKER: Boriša Kuzeljević
TITLE: Lower bounds of sets of P-points
DATE: Wednesday, 29 February 2023
TIME: 16:00 (CET)
PLACE: Room B1 (UB). The Seminar can also be followed online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


BLAST in Charlottle NC: May 16-20, 2023

Conference
We would like to bring your attention to the upcoming BLAST 2023 conference, which will take place at the University of North Carolina, Charlotte, from May 16 - 20. BLAST is a conference series focusing on Boolean Algebras, Lattices, Universal Algebra and Model Theory, Set Theory, and Topology. We hope that you will be able to attend the conference, and to contribute a talk. The confirmed invited speakers for the conference are: - Marco Abbadini, University of Salerno - Dana Bartošová, University of Florida - William Chan, University of North Texas - Daniel Herden, Baylor University - Andre Kornell, Dalhousie University - David Stanovský, Charles University Additionally, we can confirm that a tutorial will be given by - Keith Kearnes, University of Colorado Boulder The website for this conference is still under construction, but a preliminary version can be found here: https://pages.charlotte.edu/blast2023/. The home website for the BLAST conference series can be found here: https://math.colorado.edu/blast/. Some financial support, provided by the National Science Foundation, is available for students and young researchers.
Link to more info

CMU Math Logic Seminar next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, February 28, 2023

Mathematical Logic Seminar:  3:30-4:30 PM Eastern, Online, Marcin Sabok, McGill University

Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09
Meeting ID: 926 5532 4096
Passcode: 555455

TITLE: Perfect matchings in hyperfinite graphings

ABSTRACT: The talk will focus on recent results on measurable perfect matchings in hyperfinite graphings. In particular, we will discuss a result saying that every regular hyperfinite one-ended bipartite graphing admits a measurable perfect matching. We will also see some applications of these results, answering several questions in the field. For instance we will characterize the existence of factor of iid perfect matchings in bipartite Cayley graphs, extending a result of Lyons and Nazarov. We will also answer a question of Bencs, Hruskova and Toth arising in the study of balanced orientations in graphings. Finally, we see how the results imply the measurable circle squaring. This is joint work with Matt Bowen and Gabor Kun.

Logic Seminar 1 March 2023 17:00 hrs Singapore time by Linus Richter at NUS via Zoom

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 1 March 2023, 17:00 hrs Place: NUS, Department of Mathematics, Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Linus Richter, Victoria University of Wellington Title: Co-analytic Counterexamples to Marstrand's Projection Theorem Abstract: A recent "point-to-set principle" of Jack Lutz and Neil Lutz characterises the Hausdorff dimension of any subset of Euclidean space in terms of the Kolmogorov complexity of its individual points. Sets with particular fractal properties can now be constructed point-by-point, by coding "enough" information into each point, bit-by-bit. After introducing the point-to-set principle, I will present a new result in fractal geometry: under V=L (the axiom of constructiblity), I will outline the construction of co-analytic sets of Euclidean space which fail Marstrand's Projection Theorem, a classical result in fractal geometry concerning the dimension of orthogonal projections of analytic plane sets onto lines. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the morning.


Our speaker this week will be Slawomir Solecki from Cornell University. This talk is going to take place this Friday, Feb.24, 2023,  from 9am to 10am (UTC+8, Beijing time). 

Title: Descriptive Set Theory and closed groups generated by generic measure preserving transformations

Abstract: The subject matter of the talk lies within the area that employs the descriptive set theoretic point of view in the study of large topological groups. 

The behavior of a measure preserving transformation, even a generic one, is highly non-uniform. In contrast to this observation, a different picture of a very uniform behavior of the closed group generated by a generic measure preserving transformation $T$ has emerged. This picture included substantial evidence that pointed to these groups (for a generic $T$) being all topologically isomorphic to a single group, namely, $L^0$---the topological group of all Lebesgue measurable functions from $[0,1]$ to the circle. In fact, Glasner and Weiss asked if this is the case.

We will describe the background touched on above, including the descriptive set theoretic background. We will indicate a proof of the following theorem that answers the Glasner--Weiss question in the negative: for a generic measure preserving transformation $T$, the closed group generated by $T$ is {\bf not} topologically isomorphic to $L^0$.

____________________________________________________________________________________________________________________________________

This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title:                 The 17th Nankai Logic Colloquium --Slawomir Solecki

Time:                9:00am, Feb. 24, 2023 (Beijing Time)

Zoom Number:854 3647 9165

Passcode:         977845

Link:                 https://zoom.us/j/85436479165?pwd=cjFwZlpUZWtCcnhTci9OK0R5ODU0UT09

_____________________________________________________________________


Best wishes,

Ming Xiao




This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 13, 2023 - - - -

Rutgers Logic Seminar 
Monday, February 13, 2pm, Rutgers University, Hill 005
James Holland, Rutgers
Forcing more choice over the Chang model


- - - - Tuesday, Feb 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 14, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Vladimir Kanovei, Institute for Information Transmission Problems
On the significance of parameters in the choice and сomprehension schemata in the 2nd-order Peano arithmetic

Parameters are free variables in various axiom schemata in PA, ZFC, and other similar theories. Given an axiom schema S, we let S* be the parameter-free sub-schema.

Kreisel (A survey of proof theory, JSL 1968) was one of those who paid attention to the comparison of some schemata in second-order PA and their parameter-free versions. In particular, Kreisel noted that

[...] if one is convinced of the significance of something like a given axiom schema, it is natural to study details, such as the effect of parameters.

This talk is devoted to the effect of parameters in the schemata of Comprehension and Choice in second-order arithmetic.




- - - - Wednesday, Feb 15, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Special Topic:    TQFT and ComputationSecond Lecture.

Speaker:     Mee Seong Im, United States Naval Academy, Annapolis.

Date and Time:     Wednesday February 15, 2023, 7:00 - 8:30 PM. IN PERSON TALK.

Title:     Automata and topological theories.


Abstract: Theory of regular languages and finite state automata is part of the foundations of computer science. Topological quantum field theories (TQFT) are a key structure in modern mathematical physics. We will interpret a nondeterministic automaton as a Boolean-valued one-dimensional TQFT with defects labelled by letters of the alphabet for the automaton. We will also describe how a pair of a regular language and a circular regular language gives rise to a lax one-dimensional TQFT.




- - - - Thursday, Feb 16, 2023 - - - -



- - - - Friday, Feb 17, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Friday February 17, 2:00pm-3:30pm, Room 6417

Russell Miller, CUNY
Computability and the Absolute Galois Group of 

Fix a computable presentation  of the algebraic closure of the rational numbers. The absolute Galois group of the rational numbers, which is precisely the automorphism group of the field , may then be viewed as a collection of paths through a finite-branching tree. Each individual automorphism has a Turing degree. We will use known results in computability to try to build natural countable elementary subgroups of the absolute Galois group. Several intriguing questions in number theory will appear as we measure the extent to which we succeed in doing so.



Next Week in Logic at CUNY:

- - - - Monday, Feb 20, 2023 - - - -



- - - - Tuesday, Feb 21, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 21, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Alexei Miasnikov, Stevens Institute of Technology
First-order classification and non-standard models

In this talk I will discuss some recent advances in the first-order classification problem. I will touch on first-order rigidity and quasi finite axiomatization. However, the main point of the presentation is on how, in principle, one can describe all structures which are first-order equivalent to a given one. This leads to non-standard models of algebraic structures (aka non-standard analysis or non-standard arithmetic), which are interesting in their own right.




- - - - Wednesday, Feb 22, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Special Topic:    TQFT and ComputationThird Lecture.
Speaker:     Joshua Sussan, CUNY.
Date and Time:     Wednesday February 22, 2023, 7:00 - 8:30 PM. IN PERSON TALK.
Title:     Non-semisimple Hermitian TQFTs.

Abstract: Topological quantum field theories coming from semisimple categories build upon interesting structures in representation theory and have important applications in low dimensional topology and physics. The construction of non-semisimple TQFTs is more recent and they shed new light on questions that seem to be inaccessible using their semisimple relatives. In order to have potential applications to physics, these non-semisimple categories and TQFTs should possess Hermitian structures. We will define these structures and give some applications.




- - - - Thursday, Feb 23, 2023 - - - -



- - - - Friday, Feb 24, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Friday February 24, 2:00pm-3:30pm, Room 6417
Johanna Franklin, Hofstra University

When Gromov asked 'What is a typical group?', he was thinking of finitely presented groups, and he proposed an approach involving limiting density. Here, we reframe this question in the context of universal algebra and discuss some examples illustrating the behaviors of some of these algebraic varieties and then general conditions that imply some of these behaviors. Our primary general result states that for a commutative generalized bijective variety and presentations with a single generator and single identity, the zero-one law holds and, furthermore, that the sentences with density 1 are those true in the free structure. The proof of this result requires a specialized version of Gaifman's Locality Theorem that enables us to get a better bound on the complexity of the formulas of interest to us.

This work is joint with Meng-Che 'Turbo' Ho and Julia Knight.




Next Week in Logic at CUNY:

- - - - Monday, Feb 27, 2023 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 27, 4.15-6.15pm (NY time), GC room TBD
NOTE: Meetings this semester are in person only (no zoom)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Lionel Shapiro, UConn



- - - - Tuesday, Feb 28, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 28, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Zuzana Hanikova, Czech Academy of Sciences
Vopěnka's Alternative Set Theory and its mathematical context

Vopěnka first presented his Alternative Set Theory (AST) in the monograph 'Mathematics in the Alternative Set Theory' published by Teubner, Leipzig in 1979. Another book presenting the theory, 'Introduction to Mathematics in the Alternative Set Theory', was published in 1989 in Slovak by Alfa, Bratislava. In addition there are numerous journal papers on the AST by members of the research group established by Vopěnka, and the proceedings of a conference dedicated to the AST, also from 1989. In several essays, Vopěnka sought to lay out the motivation and philosophical import of the AST and some of his subsequent work. As one consequence of the emphasis on his philosophy, the mathematical inspiration for the AST has been somewhat obliterated. The aim of the talk is to discuss the design choices Vopěnka made for the AST in relation to pertinent mathematical developments of the 20th century, such as Skolem's work on nonstandard models of arithmetic, Robinson's nonstandard analysis, Rieger's nonstandard models of arithmetic, Vopěnka's nonstandard model of set theory, Vopěnka and Hájek's theory of semisets, or Parikh's almost consistent theories. The presentation will include an outline of the AST following the works of Vopěnka and Sochor. This is a historical talk; no new mathematical results on the AST will be presented.




- - - - Wednesday, Mar 1, 2023 - - - -



- - - - Thursday, Mar 2, 2023 - - - -



- - - - Friday, Mar 3, 2023 - - - -




- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 22nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- Maximal trees on P(omega)/fin Given a partial order (P,<), a tree T on P is a subset of P such that T order by the inverse order defined by <, is a tree. This notion was introduced by D. Monk some years ago, and asked about the size of maximal trees on [omega]^omega order by almost inclusion. In this talk we will review some constructions of maximal trees of cardinality omega_1 under some parametrized diamond principles and some related results. This is joint work with G. Campero, M. Hrusak and F. Miranda. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 
Please find attached the announcement of the next Barcelona Set Theory Seminar session.

SPEAKER:  On Disjoint Stationary Sequences
DATE: Wednesday, 22 February 2023
TIME: 16:00 (CET)
PLACE: Room B1 (UB). The Seminar can also be followed online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Logic Seminar Wed 15 Feb 2023 17:00 hrs at NUS by David Belanger

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 15 February 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#05-11 Speaker: David Belanger Title: A system of functionals-of-finite-type for BSigma_n models Abstract: We present a system of functionals that can serve as Skolem functions, so that any arithmetical formula can be rewritten in terms of them, in a model of BSigma_n + not ISigma_n. A distinguishing feature of our construction is that each functional is coded as a natural number within the model, and there is an upper bound on the codes. The method has a number of interesting applications. This is joint work with Chong, Li, Wong and Yang. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the afternoon.


Our speaker this week will be Riccardo Camerlo from University of Genoa. This talk is going to take place this Friday, Feb.17, 2023,  from 4 pm to 5 pm (UTC+8, Beijing time). 

Title: On some reducibility hierarchies

Abstract:
The notion of reducibility allows to compare sets or, more generally,  
relations by using a given class of functions to make the comparison.  
The choice of different classes of functions may give rise to very  
diffent hierarchies.
Purpose of the talk is to give an elementary presentation of some of  
these hierarchies, discuss some examples, and comment on some open  
problems.

___________________________________________________________________________________________________________________________________________________

This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.

Title:                 The 16th Nankai Logic Colloquium --Riccardo Camerlo

Time:                16:00pm, Feb. 17, 2023 (Beijing Time)

Zoom Number:839 6396 1742

Passcode:        321054

Link:                 https://zoom.us/j/83963961742?pwd=c2ppSXpMQks3Vit5bnZkUm5heElNUT09

_____________________________________________________________________


Best wishes,

Ming Xiao




This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 13, 2023 - - - -

Rutgers Logic Seminar 
Monday, February 13, 2pm, Rutgers University, Hill 005
James Holland, Rutgers
Forcing more choice over the Chang model


- - - - Tuesday, Feb 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 14, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Vladimir Kanovei, Institute for Information Transmission Problems
On the significance of parameters in the choice and сomprehension schemata in the 2nd-order Peano arithmetic

Parameters are free variables in various axiom schemata in PA, ZFC, and other similar theories. Given an axiom schema S, we let S* be the parameter-free sub-schema.

Kreisel (A survey of proof theory, JSL 1968) was one of those who paid attention to the comparison of some schemata in second-order PA and their parameter-free versions. In particular, Kreisel noted that

[...] if one is convinced of the significance of something like a given axiom schema, it is natural to study details, such as the effect of parameters.

This talk is devoted to the effect of parameters in the schemata of Comprehension and Choice in second-order arithmetic.




- - - - Wednesday, Feb 15, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Special Topic:    TQFT and ComputationSecond Lecture.

Speaker:     Mee Seong Im, United States Naval Academy, Annapolis.

Date and Time:     Wednesday February 15, 2023, 7:00 - 8:30 PM. IN PERSON TALK.

Title:     Automata and topological theories.


Abstract: Theory of regular languages and finite state automata is part of the foundations of computer science. Topological quantum field theories (TQFT) are a key structure in modern mathematical physics. We will interpret a nondeterministic automaton as a Boolean-valued one-dimensional TQFT with defects labelled by letters of the alphabet for the automaton. We will also describe how a pair of a regular language and a circular regular language gives rise to a lax one-dimensional TQFT.




- - - - Thursday, Feb 16, 2023 - - - -



- - - - Friday, Feb 17, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Friday February 17, 2:00pm-3:30pm, Room 6417

Russell Miller, CUNY
Computability and the Absolute Galois Group of 

Fix a computable presentation  of the algebraic closure of the rational numbers. The absolute Galois group of the rational numbers, which is precisely the automorphism group of the field , may then be viewed as a collection of paths through a finite-branching tree. Each individual automorphism has a Turing degree. We will use known results in computability to try to build natural countable elementary subgroups of the absolute Galois group. Several intriguing questions in number theory will appear as we measure the extent to which we succeed in doing so.



Next Week in Logic at CUNY:

- - - - Monday, Feb 20, 2023 - - - -



- - - - Tuesday, Feb 21, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 21, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Alexei Miasnikov, Stevens Institute of Technology
First-order classification and non-standard models

In this talk I will discuss some recent advances in the first-order classification problem. I will touch on first-order rigidity and quasi finite axiomatization. However, the main point of the presentation is on how, in principle, one can describe all structures which are first-order equivalent to a given one. This leads to non-standard models of algebraic structures (aka non-standard analysis or non-standard arithmetic), which are interesting in their own right.




- - - - Wednesday, Feb 22, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Special Topic:    TQFT and ComputationThird Lecture.
Speaker:     Joshua Sussan, CUNY.
Date and Time:     Wednesday February 22, 2023, 7:00 - 8:30 PM. IN PERSON TALK.
Title:     Non-semisimple Hermitian TQFTs.

Abstract: Topological quantum field theories coming from semisimple categories build upon interesting structures in representation theory and have important applications in low dimensional topology and physics. The construction of non-semisimple TQFTs is more recent and they shed new light on questions that seem to be inaccessible using their semisimple relatives. In order to have potential applications to physics, these non-semisimple categories and TQFTs should possess Hermitian structures. We will define these structures and give some applications.




- - - - Thursday, Feb 23, 2023 - - - -



- - - - Friday, Feb 24, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Friday February 24, 2:00pm-3:30pm, Room 6417
Johanna Franklin, Hofstra University



- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 15th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Whitehead's problem, expanded and condensed, Part 2 Whitehead's problem, which asks whether every Whitehead group is a free abelian group, was a prominent open question in group theory in the mid-20th century. In 1974, Shelah proved that the problem is independent of ZFC: if V=L, then every Whitehead group is free, whereas if Martin's Axiom and the negation of CH hold, then there is a non-free Whitehead group. This was a major surprise and was one of the first major problems coming from outside logic and set theory to be proven to be independent. Last week, we sketched a proof of Shelah's independence result. This week, we present some more recent work, focusing on the category of condensed abelian groups, introduced recently by Clausen and Scholze as an enrichment of the category of topological abelian groups with nicer algebraic properties. We will give a new, concrete, combinatorial proof of a result, due to Clausen and Scholze, stating that Whitehead's problem is not independent in the category of condensed abelian groups. We will end by using some of the ideas of this proof to highlight some potential connections between condensed mathematics and the theory of forcing. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 
Please find attached the announcement of the next Barcelona Set Theory Seminar session.

SPEAKER:  Andreas Lietz
TITLE: Forcing "NS is 
1-Dense" from Large Cardinals
DATE: Wednesday, 15 February 2023
TIME: 16:00 (CET)
PLACE: Room B1 (UB). The Seminar can also be followed online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Nankai Logic Colloquium

Nankai Logic Colloquium

Hello everyone,


This week our weekly Nankai Logic Colloquium is going to be in the afternoon.


Our speaker this week will be Anush Tserunyan from McGill University. This talk is going to take place this Friday, Feb.10, 2023,  from 4 pm to 5 pm (UTC+8, Beijing time). 

Title. A descriptive approach to pointwise ergodic theorems

Abstract. Pointwise ergodic theorems provide a bridge between the global behaviour of the dynamical system and the local combinatorial statistics of the system at a point. These theorems are powerful tools used in ergodic theory, probability, number theory, and other areas of mathematics. I will describe a new general yet elementary approach for proving such theorems, which is inspired by descriptive set theory. This approach has led to new kinds of pointwise ergodic theorems, and I will discuss those obtained in joint work with Jenna Zomback.

___________________________________________________________________________________________________________________________________________________

This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.


Title: The 15th Nankai Logic Colloquium --Anush Tserunyan
Time: 16:00pm, Feb. 10, 2023 (Beijing Time)
Zoom Number:836 2979 3119
Passcode: 476294
Link: https://us02web.zoom.us/j/83629793119?pwd=R1c4OHJReXNMTHE2dFpOOS91bnhQUT09

_____________________________________________________________________


Best wishes,

Ming Xiao




Logic Seminar Wed 8 Feb 2023 17:00 hrs at NUS via Zoom by Will Johnson

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 8 February 2023, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Will Johnson Title: NIP integral domains and Henselianity URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Is every NIP integral domain a Henselian local ring? In this talk, I will give evidence for this conjecture, sketching why it holds in the positive characteristic case and the finite dp-rank case. I will also discuss how this ``generalized Henselianity conjecture'' is related to the standard conjectures on NIP fields and valued fields. For example, the Henselianity conjecture for NIP valued fields implies the generalized Henselianity conjecture for Noetherian NIP integral domains. Lastly I will discuss how this conjecture fits into the general problem of classifying NIP fields and NIP commutative rings. For example, it implies that NIP fields with definable field topologies must be ample/large in the sense of Pop, and NIP commutative rings must be finite products of Henselian local rings.

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Note the updated email for Victoria Gitman throughout the newsletter below - please use her updated address vgitman@gmail.com.

Best,
Jonas


This Week in Logic at CUNY:

- - - - Monday, Feb 6, 2023 - - - -

Rutgers Logic Seminar 
Monday, February 6, 2pm, Rutgers University, Hill 005
Brian Pinsky, Rutgers
Hopfian groups are complete co-analytic



- - - - Tuesday, Feb 7, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 7, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Mikhail Katz, Bar Ilan University
Effective infinitesimals in R

We survey the effective foundations for analysis with infinitesimals recently developed by Hrbacek and Katz, and detail some applications. Theories SPOT and SCOT illustrate the fact that analysis with infinitesimals requires no more choice than traditional analysis. The theory SCOT incorporates in particular all the axioms of Nelson's Radically Elementary Probability Theory, which is therefore conservative over ZF+ADC.



- - - - Wednesday, Feb 8, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Special Topic:    TQFT and ComputationFirst Lecture.

Speaker:     Mikhail Khovanov, Columbia University.

Date and Time:     Wednesday February 8, 2023, 7:00 - 8:30 PM. IN PERSON TALK.

Title:     Universal construction and its applications.


Abstract: Universal construction starts with an evaluation of closed n-manifolds and builds a topological theory (a lax TQFT) for n-cobordisms. A version of it has been used for years as an intermediate step in constructing link homology theories, by evaluating foams embedded in 3-space. More recently, universal construction in low dimensions has been used to find interesting structures related to Deligne categories, formal languages and automata. In the talk we will describe the universal construction and review these developments.




- - - - Thursday, Feb 9, 2023 - - - -



- - - - Friday, Feb 10, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 10, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Davide Leonessi CUNY

Strategy and determinacy in infinite Hex

The popular game of Hex can be extended to the infinite hexagonal lattice, defining a winning condition which formalises the idea of a chain of colored stones stretching towards infinity. The descriptive-set-theoretic complexity of the set of winning positions is unknown, although it is at most Σ^1_1, and it is conjectured to be Borel; this has implications on whether games of infinite Hex are determined from all initial positions as either first-player wins or draws.

I will show that, unlike the finite game, infinite Hex with an initially empty board is a draw. But is the game still a draw when starting from a non-empty board? This open question can be partially answered in the positive by assuming the existence of certain local strategies, and in the negative by giving the advantage of placing two stones at each turn to one of the players. This is joint work with Joel David Hamkins.





Logic Workshop
CUNY Graduate Center
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Friday February 10, 2:00pm-3:30pm, Room 6417

Athar Abdul-Quader, Purchase College
Satisfaction and saturation

It is well known that a countable model of PA has a truth predicate if and only if it is recursively saturated. It is also well known that not all countable recursively saturated models of PA have *inductive* or even -inductive truth predicates: indeed, such models must satisfy Con(PA), for example. Recent work by Enayat-Pakhomov and Cieśliński-Łełyk-Wcisło explored the principle of 'disjunctive correctness', asserting that every disjunction is true if and only if it has a true disjunct. In particular, one can show that every countable model of PA has a 'disjunctively trivial' elementary extension: that is, an elementary extension with a truth predicate in which all nonstandard length disjunctions are evaluated as true. In this talk, we will see that such 'disjunctively trivial' models are necessarily arithmetically saturated; indeed, we will see that a countable model of PA is arithmetically saturated if and only if it has a disjunctively trivial truth predicate. We will explore related pathologies in truth predicates, and classify the sets which can be defined using such pathologies. We find other surprising connections between arithmetic saturation and these questions of definability. This is joint work with Mateusz Łełyk, based heavily on unpublished work by Jim Schmerl.



Next Week in Logic at CUNY:

- - - - Monday, Feb 13, 2023 - - - -

Rutgers Logic Seminar 
Monday, February 13, 2pm, Rutgers University, Hill 005
James Holland, Rutgers



- - - - Tuesday, Feb 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 14, 1:00pm
Virtual (email Victoria Gitman vgitman@gmail.com for meeting id)

Vladimir Kanovei, Institute for Information Transmission Problems
On the significance of parameters in the choice and сomprehension schemata in the 2nd-order Peano arithmetic

Parameters are free variables in various axiom schemata in PA, ZFC, and other similar theories. Given an axiom schema S, we let S* be the parameter-free sub-schema.

Kreisel (A survey of proof theory, JSL 1968) was one of those who paid attention to the comparison of some schemata in second-order PA and their parameter-free versions. In particular, Kreisel noted that

[...] if one is convinced of the significance of something like a given axiom schema, it is natural to study details, such as the effect of parameters.

This talk is devoted to the effect of parameters in the schemata of Comprehension and Choice in second-order arithmetic.




- - - - Wednesday, Feb 15, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Special Topic:    TQFT and ComputationFirst Lecture.

Speaker:     Mee Seong Im, United States Naval Academy, Annapolis.

Date and Time:     Wednesday February 15, 2023, 7:00 - 8:30 PM. IN PERSON TALK.

Title:     Automata and topological theories.


Abstract: Theory of regular languages and finite state automata is part of the foundations of computer science. Topological quantum field theories (TQFT) are a key structure in modern mathematical physics. We will interpret a nondeterministic automaton as a Boolean-valued one-dimensional TQFT with defects labelled by letters of the alphabet for the automaton. We will also describe how a pair of a regular language and a circular regular language gives rise to a lax one-dimensional TQFT.




- - - - Thursday, Feb 16, 2023 - - - -



- - - - Friday, Feb 17, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Friday February 17, 2:00pm-3:30pm, Room 6417

Russell Miller, CUNY
Computability and the Absolute Galois Group of 

Fix a computable presentation  of the algebraic closure of the rational numbers. The absolute Galois group of the rational numbers, which is precisely the automorphism group of the field , may then be viewed as a collection of paths through a finite-branching tree. Each individual automorphism has a Turing degree. We will use known results in computability to try to build natural countable elementary subgroups of the absolute Galois group. Several intriguing questions in number theory will appear as we measure the extent to which we succeed in doing so.



- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 6, 2023 - - - -

Rutgers Logic Seminar 
Monday, February 6, 2pm, Rutgers University, Hill 005
Brian Pinsky, Rutgers
Hopfian groups are complete co-analytic



- - - - Tuesday, Feb 7, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 7, 1:00pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Mikhail Katz, Bar Ilan University
Effective infinitesimals in R

We survey the effective foundations for analysis with infinitesimals recently developed by Hrbacek and Katz, and detail some applications. Theories SPOT and SCOT illustrate the fact that analysis with infinitesimals requires no more choice than traditional analysis. The theory SCOT incorporates in particular all the axioms of Nelson's Radically Elementary Probability Theory, which is therefore conservative over ZF+ADC.



- - - - Wednesday, Feb 8, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Special Topic:    TQFT and ComputationFirst Lecture.

Speaker:     Mikhail Khovanov, Columbia University.

Date and Time:     Wednesday February 8, 2023, 7:00 - 8:30 PM. IN PERSON TALK.

Title:     Universal construction and its applications.


Abstract: Universal construction starts with an evaluation of closed n-manifolds and builds a topological theory (a lax TQFT) for n-cobordisms. A version of it has been used for years as an intermediate step in constructing link homology theories, by evaluating foams embedded in 3-space. More recently, universal construction in low dimensions has been used to find interesting structures related to Deligne categories, formal languages and automata. In the talk we will describe the universal construction and review these developments.




- - - - Thursday, Feb 9, 2023 - - - -



- - - - Friday, Feb 10, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 10, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Davide Leonessi CUNY

Strategy and determinacy in infinite Hex

The popular game of Hex can be extended to the infinite hexagonal lattice, defining a winning condition which formalises the idea of a chain of colored stones stretching towards infinity. The descriptive-set-theoretic complexity of the set of winning positions is unknown, although it is at most Σ^1_1, and it is conjectured to be Borel; this has implications on whether games of infinite Hex are determined from all initial positions as either first-player wins or draws.

I will show that, unlike the finite game, infinite Hex with an initially empty board is a draw. But is the game still a draw when starting from a non-empty board? This open question can be partially answered in the positive by assuming the existence of certain local strategies, and in the negative by giving the advantage of placing two stones at each turn to one of the players. This is joint work with Joel David Hamkins.





Logic Workshop
CUNY Graduate Center
Hybrid: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Friday February 10, 2:00pm-3:30pm, Room 6417

Athar Abdul-Quader, Purchase College
Satisfaction and saturation

It is well known that a countable model of PA has a truth predicate if and only if it is recursively saturated. It is also well known that not all countable recursively saturated models of PA have *inductive* or even -inductive truth predicates: indeed, such models must satisfy Con(PA), for example. Recent work by Enayat-Pakhomov and Cieśliński-Łełyk-Wcisło explored the principle of 'disjunctive correctness', asserting that every disjunction is true if and only if it has a true disjunct. In particular, one can show that every countable model of PA has a 'disjunctively trivial' elementary extension: that is, an elementary extension with a truth predicate in which all nonstandard length disjunctions are evaluated as true. In this talk, we will see that such 'disjunctively trivial' models are necessarily arithmetically saturated; indeed, we will see that a countable model of PA is arithmetically saturated if and only if it has a disjunctively trivial truth predicate. We will explore related pathologies in truth predicates, and classify the sets which can be defined using such pathologies. We find other surprising connections between arithmetic saturation and these questions of definability. This is joint work with Mateusz Łełyk, based heavily on unpublished work by Jim Schmerl.



Next Week in Logic at CUNY:

- - - - Monday, Feb 13, 2023 - - - -

Rutgers Logic Seminar 
Monday, February 13, 2pm, Rutgers University, Hill 005
James Holland, Rutgers



- - - - Tuesday, Feb 14, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, February 14, 1:00pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Vladimir Kanovei, Institute for Information Transmission Problems
On the significance of parameters in the choice and сomprehension schemata in the 2nd-order Peano arithmetic

Parameters are free variables in various axiom schemata in PA, ZFC, and other similar theories. Given an axiom schema S, we let S* be the parameter-free sub-schema.

Kreisel (A survey of proof theory, JSL 1968) was one of those who paid attention to the comparison of some schemata in second-order PA and their parameter-free versions. In particular, Kreisel noted that

[...] if one is convinced of the significance of something like a given axiom schema, it is natural to study details, such as the effect of parameters.

This talk is devoted to the effect of parameters in the schemata of Comprehension and Choice in second-order arithmetic.




- - - - Wednesday, Feb 15, 2023 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Special Topic:    TQFT and ComputationFirst Lecture.

Speaker:     Mee Seong Im, United States Naval Academy, Annapolis.

Date and Time:     Wednesday February 15, 2023, 7:00 - 8:30 PM. IN PERSON TALK.

Title:     Automata and topological theories.


Abstract: Theory of regular languages and finite state automata is part of the foundations of computer science. Topological quantum field theories (TQFT) are a key structure in modern mathematical physics. We will interpret a nondeterministic automaton as a Boolean-valued one-dimensional TQFT with defects labelled by letters of the alphabet for the automaton. We will also describe how a pair of a regular language and a circular regular language gives rise to a lax one-dimensional TQFT.




- - - - Thursday, Feb 16, 2023 - - - -



- - - - Friday, Feb 17, 2023 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Friday February 17, 2:00pm-3:30pm, Room 6417

Russell Miller, CUNY
Computability and the Absolute Galois Group of 

Fix a computable presentation  of the algebraic closure of the rational numbers. The absolute Galois group of the rational numbers, which is precisely the automorphism group of the field , may then be viewed as a collection of paths through a finite-branching tree. Each individual automorphism has a Turing degree. We will use known results in computability to try to build natural countable elementary subgroups of the absolute Galois group. Several intriguing questions in number theory will appear as we measure the extent to which we succeed in doing so.



- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 8th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Whitehead's problem, expanded and condensed Whitehead's problem, which asks whether every Whitehead group is a free abelian group, was a prominent open question in group theory in the mid-20th century. In 1974, Shelah proved that the problem is independent of ZFC: if V=L, then every Whitehead group is free, whereas if Martin's Axiom and the negation of CH hold, then there is a non-free Whitehead group. This was a major surprise and was one of the first major problems coming from outside logic and set theory to be proven to be independent. In recent years, Clausen and Scholze have introduced the category of condensed abelian groups, which can be seen as an enrichment of the category of topological abelian groups with nicer algebraic properties. Through some deep structural analysis of this category, they showed that, when appropriately interpreted, Whitehead's problem is not independent in the category of condensed abelian groups; it is provable in ZFC that every abelian group that is Whitehead in the condensed category must be free. In the first half of the talk, we will introduce Whitehead's problem and provide a sketch of Shelah's proof. In the second half, we will give a new, concrete, combinatorial proof of Clausen and Scholze's result. No knowledge of algebra will be assumed of the audience; all proofs will involve only set theoretic techniques and very basic group theory. Best, David

Core model seminar next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, February 7, 2023

Core Model Seminar:  1:30-3 PM Eastern Online, Gabriel Goldberg, University of California, Berkeley

Join Zoom Meeting: https://cmu.zoom.us/j/97749733438?pwd=Yk5PcSsvekptWWxMNUhCU2pFbzA0Zz09
Meeting ID: 977 4973 3438
Passcode: 457791

TITLE: Inner models from stationary logic, part 1

ABSTRACT: We discuss the inner model C(aa) introduced by Kennedy-Magidor-Väänänen, and answer several questions posed in their paper  "Inner models from strong logics". Assuming large cardinal axioms, we'll show that this model satisfies GCH (this is joint work with John Steel) and that C(aa) satisfies o(κ) = κ++ for all regular cardinals κ > ω1 (this is joint work with Otto Rajala).

CMU math logic seminar next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, February 7, 2023

Mathematical Logic Seminar:  3:30-4:30 PM Eastern, Online, Tom Benhamou, University of Illinois at Chicago

Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09
Meeting ID: 926 5532 4096
Passcode: 555455

TITLE: Saturation properties of ultrafilters

ABSTRACT: In this talk, we will focus on certain saturation properties of filters and ultrafilters which generalizes the so-called Galvin property. In the first part of the talk, we will present a connection between such ultrafilters and the existence of Slim-Kurepa trees. We will then present several results regarding the existence of non-Galvin ultrafilters under several large cardinal assumptions. Finally, if time permits, we will present a recent application to canonical inner models and some open related questions.

Logic Seminar 1 Feb 2023 17:00 hrs at NUS by Yu Liang, Nanjing University

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 1 February 2023, 17:00 hrs Place: NUS, Department of Mathematics, S17#05-11 Speaker: Yu Liang Title: Some applications of recursion theory to set theory Abstract: I shall present some recent results in set theory which are based on proof methods and results from recursion theory. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Reminder for today's Talk

NUS Logic Seminar
The following logic semianr talk is today (now) at 17:00 hrs Singapore time; the talk is only by Zoom. The Zoom Login is this: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Title and Abstract of today's talk can be found on the following webpage of the logic seminar: https://www.comp.nus.edu.sg/~fstephan/logicseminar.html The title is: Regressive versions of Hindman's Theorem. The speaker is: Leonardo Mainardi. You find on this link also the still free time-slots; if any of you wants to give a talk from overseas, we will make it on Zoom as well; local speakers can also give a physical talk in the meeting. Best regards, Frank

Cross-Alps Logic Seminar (speaker: Katarzyna Kowalik)

Cross-Alps Logic Seminar
On Friday 27.01.2023 at 16:00
Katarzyna Kowalik (University of Warsaw)
will give a talk on
Reverse mathematics of some Ramsey-theoretic principles over a weak base theory

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

This Week in Logic at CUNY

This Week in Logic at CUNY
The CUNY semester starts this week - welcome back, everyone!  I want to draw particular attention to the Fitting at 80 Conference taking place this Saturday, January 28th (see below for details).

Best,
Jonas Reitz



This Week in Logic at CUNY:

- - - - Monday, Jan 23, 2023 - - - -

Rutgers Logic Seminar 
Monday, January 23, 2pm, Rutgers University, Hill 005
Chris Laskowski (University of Maryland) 
The Borel complexity of modules


- - - - Tuesday, Jan 24, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, January 24, 1:00pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Karel Hrbacek, CUNY
Representation of unlimited integers

Nonstandard methods have been successfully applied to standard problems in number theory by R. Jin, T. Tao and others. A. Boudaoud and D. Bellaouar are pursuing the opposite direction: they are formulating number-theoretic problems in the language of nonstandard analysis and solving them by standard methods. Two examples of the kind of questions they consider are:
(1) Can every unlimited natural number n be represented in the form n = s + w_1w_2 where s is a limited integer and w_1, w_2 are unlimited?
(2) Can every unlimited natural number n be represented in the form n = w_1w_2 + w_3w_4 so that each ratio w_i / w_j is appreciable (ie, neither infinitesimal nor unlimited)?
I give a negative answer to question (1) (assuming Dickson’s Conjecture) and a positive answer to question (2).
A. Boudaoud, D. Bellaouar, Representation of integers: A nonclassical point of view, Journal of Logic & Analysis. 12:4 (2020) 1{31; K. Hrbacek, Journal of Logic & Analysis 12:5 (2020) 1–6.




- - - - Wednesday, Jan 25, 2023 - - - -



- - - - Thursday, Jan 26, 2023 - - - -



- - - - Friday, Jan 27, 2023 - - - -


- - - - Saturday, Jan 28, 2023 - - - -

Fitting at 80
Saturday, January 28

A prominent logician Melvin Fitting has turned 80. This online conference is a special event in his honor. Melvin Fitting was in the departments of Computer Science, Philosophy, and Mathematics at the CUNY Graduate Center and in the department of Mathematics and Computer Science at Lehman College. He is now Professor Emeritus. He has authored 11 books and over a hundred research papers with staggering citation figures. In 2012 Melvin Fitting was given the Herbrand Award by the Conference on Automated Deduction (CADE) for distinguished contributions to the field.

Greetings, congratulations, photos for posting, and ZOOM link requests could be sent to Sergei Artemov by sartemov@gmail.com or sartemov@gc.cuny.edu.

Conference website https://sartemov.ws.gc.cuny.edu/fitting-at-80/

Program (the times are given in the Eastern Day Time zone EST).
January 28, Saturday
8:00-8:45 am Arnon Avron (Tel Aviv), “Breaking the Tie: Benacerraf’s Identification Argument Revisited”
8:45-9:30 am Junhua Yu (Beijing), "Exploring Operators on Neighborhood Models"
9:45-10:30 am Sara Negri (Genoa), "Faithful Modal Embedding: From Gödel to Labelled Calculi"
10:30-11:15 am Heinrich Wansing (Bochum), “Remarks on Semantic Information and Logic. From Semantic Tetralateralism to the Pentalattice 65536_5”
11:30 am -12:15 pm Roman Kuznets (Vienna), "On Interpolation"
12:15-1:00 pm Walter Carnielli (Campinas), “Combining KX4 and S4: A Logic That Encompasses Factive and Non-factive Evidence”
1:15-2:00 pm Eduardo Barrio and Federico Pailos (Buenos Aires), “Meta-classical Non-classical Logics”
2:00-2:45 pm Graham Priest (New York), "Jaśkowski and the Jains: a Fitting Tribute"
2:45-4:00 pm Session of memories and congratulations featuring Sergei Artemov, Hiroakira Ono, Anil Nerode, Melvin Fitting, and others.







Next Week in Logic at CUNY:

- - - - Monday, Jan 30, 2023 - - - -



- - - - Tuesday, Jan 31, 2023 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, January 31, 1:00pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Lorenzo Galeotti, Amsterdam University College
Order types of models of arithmetic without induction

It is a well-known fact that non-standard models of Peano Arithmetic (PA) have order type N + Z · D, where D is a dense linear order. The question of which dense linear orders D can occur in such order types is non-trivial and widely studied. In this context Friedman asked the following question:

Are there consistent extensions of Peano Arithmetic T and T′ such that the class of order types of models of T and the class of order types of models of T′ differ?

Friedman’s question is very complex and still wide open. In this talk we will go in the opposite direction and consider a version of Friedman’s question for syntactic fragments of PA. We will present results from a joint work with Benedikt Löwe on order types of non-standard models of syntactic subsystems of arithmetic obtained by restricting the language to subsets of the operations. We will put particular emphasis on models of syntactic subsystems of Peano Arithmetic obtained by dropping the schema of induction.



- - - - Wednesday, Feb 1, 2023 - - - -



- - - - Thursday, Feb 2, 2023 - - - -



- - - - Friday, Feb 3, 2023 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 3, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Jing Zhang, University of Toronto



- - - - Other Logic News - - - -


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 25th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Bradley-Williams -- Limits of betweenness relations and their automorphism groups Some permutation groups are best represented/constructed as kinds-of-products of or limits of simpler permutation groups. We discuss joint work with John Truss (Leeds) in which we construct a family of structures called "limits of betweenness relations" as a kind of tree-limit of trees (for appropriate combinatorial meanings of the word "tree"). A crucial part of the construction is an particular instance of categorical Fraissé Theory. Further we plan to say how their automorphism groups fit into the landscape of infinite primitive Jordan permutation groups and the structure theory of Jordan groups established by S. Adeleke, D. Macpherson, and P. M. Neumann. Best, David PS: Let me also remind you the joint Logic Seminar/Colloquium of the MLTCS department on Monday January 23rd, 16:00, Institute of Mathematics CAS, blue lecture room on the ground floor of the rear building. After the lecture we will go to a pub. Niel Thapen -- Bounded arithmetic and witnessing A witnessing theorem lets you recover, from a proof that an object exists, an algorithm to construct such an object. I will introduce the weak arithmetic theory S^1_2 and describe a simple model-theoretic proof of Buss's witnessing theorem, connecting this theory with polynomial time computations, with some unprovability results that follow from this. I will discuss some open problems about witnessing for stronger bounded theories.

(KGRC) guests, video, and a talk on Thursday, January 26

Kurt Godel Research Center
The KGRC welcomes as guests: Martin Hils (host: Matthias Aschenbrenner) visits the KGRC until March 31 and gives a talk on January 26, see below. Franz-Viktor Kuhlmann (host: Matthias Aschenbrenner) visits the KGRC until January 31. Jonathan Schilhan (host: Thilo Weinert) visits the KGRC until January 31. Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Jerzy Kąkol (host: Damian Sobota) visits the KGRC from February 27 to March 3. Manuel López Pellicer (host: Damian Sobota) visits the KGRC from February 27 to March 3. Juris Steprāns (host: Vera Fischer) visits the KGRC from March 6 to March 10 and gives a two-part talk, details to be announced at a later time. * * * For some seminar talks, video recordings are available: "Introduction to big Ramsey degrees" by David Chodounský: https://univienna.zoom.us/rec/share/he-aDDiZDHZJ8Y4Zn_FjiIwdbOf0VN6UKJrxWC7xXAEf6CG_k6Cu_QfM3gQGzwsd.wYq8tUjxaZFywaFK Pass code: @&61nNnR "The weak Ramsey property" by Wiesław Kubiś: https://univienna.zoom.us/rec/share/VeLRgmK7tBdTUOLxgzKjPhh20ErRsjUWp7v6hkNpZtM9Gxe3Xu73_Cc_iTF_AYpL.zDpkipMb7P_vKHwO Pass code: +MkI4HUc "A weak form of Global Choice under the GCH, part II" by Peter Holy: https://univienna.zoom.us/rec/share/xVaRaaDknVfPsyI6D_XZtFsxMjHr8bYSXbup0r6knM3oojoSAFdjipHgPOzN5jVw.8N-UyUkiL2g_6IJj Pass code: gS3%+Hy2 * * * Logic Colloquium Kurt Gödel Research Center Thursday, January 26 "Lang-Weil type bounds in finite difference fields" Martin Hils (Universität Münster, DE) We establish Lang-Weil type bounds for the number of rational points of difference varieties over finite difference fields, in terms of the transformal dimension of the variety and assuming the existence of a smooth rational point. It follows that, working in any non-principle ultraproduct $K$ of finite difference fields, the normalized pseudofinite dimension of a quantifier free partial type $p$ is equal to the transformal dimension of $p$, i.e., to the maximal transformal transcendence degree over $K$ of a realization of $p$. This is joint work with Ehud Hrushovski, Jinhe Ye and Tingxiang Zou. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. (Students at Uni Wien are required to attend in person.) Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Zoom session to vera.fischer@univie.ac.at.)

Logic Seminar Wed 18 Jan 2023 17:00 hrs at NUS by Bakhadyr Khoussainov

NUS Logic Seminar
Hello, there was a mistake, the talk is only in Zoom. Please use this login (also below): > > Link to join the Zoom Meeting > > https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 > > > > Meeting ID: 830 4925 8042 > > Passcode: 1729=x3+y3 Sorry for the confusion caused. Regards, Frank Stephan On Thu, Jan 12, 2023 at 03:01:35PM +0800, Frank STEPHAN wrote: > Invitation to the Logic Seminar at the National University of Singapore > > Date: Wednesday, 18 January 2022, 17:00 hrs > > Place: NUS, Department of Mathematics, S17#04-05 > Talk via Zoom: > https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 > Meeting ID: 830 4925 8042 > Passcode: 1729=x3+y3 > > Speaker: Bakhadyr Khoussainov > > Title: Definability of algorithmically presented structures. > > URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html > > We aim to describe the isomorphism types of algorithmically > presented structures in the language of the first order logic. > This is one of the key research topics related to the expressive > power of the first order logic. The focus is on two classes > of structures. The first class is the class of structures for > which the positive atomic diagrams are computably enumerable. > We call these structures positive structures. The second class > is the class of structures for which the negative atomic diagrams > are computably enumerable. We call these structures negative > structures. We investigate definability of positive and negative > structures by sets of sentences quantified with Existential, > Universal, Existential-Universal and Universal-Existential > quantifiers using expansions of languages. >

Descriptive Set Theory and Dynamics: Warsaw, Poland, August 14-25, 2023

Conference
In August 2023 a workshop and a conference on descriptive set theory and dynamics will take place in Warsaw: Workshop (14-18.08.2023, Warsaw) Conference (21-25.08.2023, Warsaw) Both are organized within the thematic semester STRUCTURES devoted to various areas of foundations of mathematics and computer science https://www.impan.pl/en/activities/banach-center/conferences/23-simons-08
Link to more info

CMU Math Logic Seminar next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, January 24, 2023 Mathematical Logic Seminar: 3:30-4:30 PM Eastern, Online, Paolo Marimon, Imperial College London Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Invariant Keisler measures in simple omega-categorical structures ABSTRACT: We study invariant Keisler measures in the context of omega-categorical structures. For a first-order structure M, these are finitely additive probability measures on the Boolean algebra of definable subsets Def_x(M) which are invariant under the action of the automorphism group Aut(M). A natural notion of smallness for a definable subset of M is that it is assigned measure 0 by any invariant Keisler measure. Another natural model-theoretic notion of smallness is forking over the empty set. These two notions coincide in various classes of structures, including stable and NIP omega-categorical ones. In a recent article, Chernikov, Hrushovski, Kruckman, Krupinski, Moconja, Pillay and Ramsey find the first examples of simple structures with formulas which do not fork over the empty set but are universally measure zero. I give the first known simple omega-categorical examples exhibiting this property. These are various omega-categorical Hrushovski constructions. In order to prove this, I use a probabilistic independence result by Jahel and Tsankov to show that a stronger version of the independence theorem holds for simple omega-categorical structures where a formula forks over the empty set if and only if it is universally measure zero.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 18th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There will be a joint Logic Seminar/Colloquium of the MLTCS department on Monday January 23rd, 16:00, Institute of Mathematics CAS, blue lecture room on the ground floor of the rear building. After the lecture we will go to a pub. Everybody will be welcome! Wednesday program: Adam Bartoš -- Isosceles-free homogeneous metric spaces While studying metric spaces in the context of Fraïssé theory we have considered the class of isosceles-free metric spaces: the spaces containing no nondegenerate isosceles triangles. All finite isoceles-free spaces form a hereditary class without weak amalgamation property. Every 1-homogeneous isosceles-free space is already ultrahomogeneous, and we can characterize all such spaces. There are also related decompositions of metric spaces giving bounds on the maximal number of distinct distances in a finite ultrahomogeneous metric space. This is joint work with Christian Bargetz, Wiesław Kubiś, and Franz Luggin. MLTCS seminar: Niel Thapen -- Bounded arithmetic and witnessing A witnessing theorem lets you recover, from a proof that an object exists, an algorithm to construct such an object. I will introduce the weak arithmetic theory S^1_2 and describe a simple model-theoretic proof of Buss's witnessing theorem, connecting this theory with polynomial time computations, with some unprovability results that follow from this. I will discuss some open problems about witnessing for stronger bounded theories. Best, David

(KGRC) Set Theory Seminar talk on Tuesday, January 17

Kurt Godel Research Center
The KGRC welcomes as guests: Martin Hils (host: Matthias Aschenbrenner) visits the KGRC until March 31, 2023 and gives a talk on January 26, 2023 (details to be announced at a later time). Franz-Viktor Kuhlmann (host: Matthias Aschenbrenner) visits the KGRC until January 31, 2023. Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Tomasz Żuchowski (host: Damian Sobota) visits the KGRC until January 17. Jerzy Kąkol (host: Damian Sobota) visits the KGRC from February 27 to March 3. Manuel López Pellicer (host: Damian Sobota) visits the KGRC from February 27 to March 3. Juris Steprāns (host: Vera Fischer) visits the KGRC from March 6 to March 10 and gives a two-part talk (details to be announced at a later time). * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, January 17 "A weak form of Global Choice under the GCH, part 2" Peter Holy (TU Wien) In 2012, Joel Hamkins asked (on MathOverflow) whether it is possible for the universe of sets to have a linear ordering, but no wellordering (that is, global choice fails). This question, which I consider very interesting, appears to still be open. In my talk, I want to present a somewhat related result. After providing a gentle introduction to second order set theory and the principle of global choice (no knowledge on these matters is assumed), we consider a different weakening of global choice under the GCH: The minimal ordinal-connection axiom MOC due to Rodrigo Freire. It is equivalent to the statement that the universe of sets can be stratified by a subset-increasing hierarchy with each K_alpha of the same size as alpha, and such that K_kappa=H(kappa), the collection of sets of hereditary size less than kappa, for every regular infinite cardinal kappa. In this form, it clearly implies the GCH, and is easily seen to be a weak form of global choice under the GCH. We will show, using class forcing products of adding Cohen subsets of regular cardinals (without assuming any particular knowledge regarding the technique of class forcing), that MOC can consistently fail in models of the GCH, and that MOC can consistently hold while global choice fails. This is joint work with Rodrigo Freire (University of Brasilia). Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. (Students at Uni Wien are required to attend in person.) Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar to vera.fischer@univie.ac.at.)

Logic Seminar Wed 18 Jan 2023 17:00 hrs at NUS by Bakhadyr Khoussainov

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 18 January 2022, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Bakhadyr Khoussainov Title: Definability of algorithmically presented structures. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html We aim to describe the isomorphism types of algorithmically presented structures in the language of the first order logic. This is one of the key research topics related to the expressive power of the first order logic. The focus is on two classes of structures. The first class is the class of structures for which the positive atomic diagrams are computably enumerable. We call these structures positive structures. The second class is the class of structures for which the negative atomic diagrams are computably enumerable. We call these structures negative structures. We investigate definability of positive and negative structures by sets of sentences quantified with Existential, Universal, Existential-Universal and Universal-Existential quantifiers using expansions of languages.

Core Model Seminar starting again in two weeks

Carnegie Mellon Logic Seminar
TUESDAY, January 24, 2023 Core Model Seminar: 1:30-3 PM Eastern, Online, Takehiko Gappo, TU Wien Join Zoom Meeting: https://cmu.zoom.us/j/97749733438?pwd=Yk5PcSsvekptWWxMNUhCU2pFbzA0Zz09 Meeting ID: 977 4973 3438 Passcode: 457791 TITLE: Chang models over derived models ABSTRACT: We will give a proof outline of the main theorem in Sargsyan's paper, "Covering with Chang models over derived models." In this paper, he constructed a new model of determinacy extending the derived model, called the Chang model over the derived model, inside of a symmetric extension of a least branch hod mouse with Woodin cardinals. This result will be used in the next talk. TUESDAY, January 31, 2023 Core Model Seminar: 1:30-3 PM Eastern, Online, Takehiko Gappo, TU Wien Join Zoom Meeting: https://cmu.zoom.us/j/97749733438?pwd=Yk5PcSsvekptWWxMNUhCU2pFbzA0Zz09 Meeting ID: 977 4973 3438 Passcode: 457791 TITLE: Determinacy in the Chang model from a hod pair ABSTRACT: We will show that the Chang model satisfies determinacy from the existence of an excellent least branch hod pair with a Woodin limit of Woodin cardinals. The proof is based on Sargsyan's result on Chang models over derived models. This is joint work with Sargsyan. TUESDAY, February 7, 2023 Core Model Seminar: 1:30-3 PM Eastern, Online, Gabriel Goldberg, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/97749733438?pwd=Yk5PcSsvekptWWxMNUhCU2pFbzA0Zz09 Meeting ID: 977 4973 3438 Passcode: 457791 TITLE: TBA; ABSTRACT: TBA TUESDAY, February 14, 2023 Core Model Seminar: 1:30-3 PM Eastern, Online, Gabriel Goldberg, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/97749733438?pwd=Yk5PcSsvekptWWxMNUhCU2pFbzA0Zz09 Meeting ID: 977 4973 3438 Passcode: 457791 TITLE: TBA; ABSTRACT: TBA

Cross-Alps Logic Seminar for World Logic Day (speaker: Vasco Brattka)

Cross-Alps Logic Seminar

On Friday 13.01.2023 at 16:00

on the occasion of World Logic Day 2023, a special session of the Cross-Alps Logic Seminars will take place, with special guest
Vasco Brattka (Universität der Bundeswehr München)
who will give a talk on
Some fascinating topics in logic around reducibilities

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to vincenzo.dimonte [at] uniud [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'. 

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 11th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jaroslav Supina -- Katětov order on ideals and the Fréchet-Urysohn property We show that the Katětov order on ideals on natural numbers is a useful tool in answering a question posed by J. Gerlits and Zs. Nagy and two questions by M. Sakai. The questions are related to local topological properties of a space of all continuous functions on an underlying topological space, the most known among them being the Fréchet-Urysohn property. This is a joint work with S. Bardyla and L. Zdomskyy. Best, David

(KGRC) seminar talks Tuesday, January 10 and Thursday, January 12

Kurt Godel Research Center
The KGRC welcomes as guests: Martin Hils (host: Matthias Aschenbrenner) visits the KGRC until March 31, 2023 and gives a talk on January 19, 2023 (details to be announced at a later time). Franz-Viktor Kuhlmann (host: Matthias Aschenbrenner) visits the KGRC until January 31, 2023. Clifton Ealy (host: Matthias Aschenbrenner) visits the KGRC until August 15. Tomasz Żuchowski (host: Damian Sobota) visits the KGRC from January 9 to January 17. Jerzy Kąkol (host: Damian Sobota) visits the KGRC from February 27 to March 3. Manuel López Pellicer (host: Damian Sobota) visits the KGRC from February 27 to March 3. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, January 10 "A weak form of Global Choice under the GCH, part 1" Peter Holy (TU Wien) In 2012, Joel Hamkins asked (on MathOverflow) whether it is possible for the universe of sets to have a linear ordering, but no wellordering (that is, global choice fails). This question, which I consider very interesting, appears to still be open. In my talk, I want to present a somewhat related result. After providing a gentle introduction to second order set theory and the principle of global choice (no knowledge on these matters is assumed), we consider a different weakening of global choice under the GCH: The minimal ordinal-connection axiom MOC due to Rodrigo Freire. It is equivalent to the statement that the universe of sets can be stratified by a subset-increasing hierarchy with each K_alpha of the same size as alpha, and such that K_kappa=H(kappa), the collection of sets of hereditary size less than kappa, for every regular infinite cardinal kappa. In this form, it clearly implies the GCH, and is easily seen to be a weak form of global choice under the GCH. We will show, using class forcing products of adding Cohen subsets of regular cardinals (without assuming any particular knowledge regarding the technique of class forcing), that MOC can consistently fail in models of the GCH, and that MOC can consistently hold while global choice fails. This is joint work with Rodrigo Freire (University of Brasilia). Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. (Students at Uni Wien are required to attend in person.) Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 For details about how to join the Zoom session, please see the end of this message. * * * Logic Colloquium Kurt Gödel Research Center Thursday, January 12 "Order-preserving Martin's Conjecture" Benjamin Siskind (Carnegie Mellon University, US) We'll talk about the current status of Martin's Conjecture, a conjecture positing that, up to equivalence almost-everywhere, the only natural functions on the Turing Degrees are the well-known ones: constant functions, the identity, and transfinite iterates of the Turing Jump. While the full conjecture is open even for low-level Borel functions, the order-preserving case seems much more tractable. We'll discuss recent progress on this order-preserving version of Martin's Conjecture. This is joint work with Patrick Lutz. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. (Students at Uni Wien are required to attend in person.) Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom for both talks: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Zoom meeting(s) to vera.fischer@univie.ac.at.)

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 4th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- Ideal independent families and ultrafilters A family X of infinite subsets of natural numbers is an ideal independent family if no element of X is almost contained in the union of finitely many other sets in the family X. The ideal independence number, s_mm, is defined as the minimal cardinality of an ideal independent family. These notions were introduced by D. Monk several years ago, and in joint work with O. Guzmán and A. Miller it was proved that the dominating number is a lower bound for s_mm, among other things. In recent work with V. Fischer and C. B. Switzer it was proved that the ultrafilter number is a lower bound for s_mm, that the spectrum of ideal independent families can be quite wide and also a preservation theorem for ideal independent families along countable support iterations. In this talk we will review some of these results. Best, David