Set Theory Talks

Global set theory seminar and conference announcements

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)

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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