Set Theory Talks

Global set theory seminar and conference announcements

(KGRC) Logic Colloquium talk Thursday, June 2

Kurt Godel Research Center
The KGRC welcomes as guests: David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21. Details for this talk will be announced later. Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC until May 31. James Mitchell (host: Vera Fischer) visits the KGRC until May 28. Yann Peresse (host: Serhii Bardyla) visits the KGRC until May 28. Luke Elliott (host: Lyubomyr Zdomskyy) visits the KGRC until May 28. Gunter Fuchs (host: Vera Fischer) visits the KGRC from June 12 to June 18 and gives a talk on June 14. Details for this talk will be announced later. Alessandro Vignati (host: Vera Fischer) visits the KGRC from June 30 to July 1 and gives a talk on June 30. Details for this talk will be announced later. Leandro Aurichi (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to August 6. Peter Nyikos (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to July 22. Frank Tall (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to July 22. * * * Please note that there will be no talk in the Set Theory Research Seminar on Tuesday, May 31. * * * Logic Colloquium Kurt Gödel Research Center Thursday, June 2 "The metamathematics of $\Pi^1_2$ sentences" Juan Aguilera (TU Wien) We will survey some recent results on the metamathematics of $\Pi^1_2$ sentences. Most of the work involves a kind of Proof Theory analogous to classical ordinal analysis, but focused on a $\Pi^1_2$ notion instead. The talk will be aimed at a general logic audience. Topics will include: proof-theoretic $\Pi^1_2$-norms, a characterization of the $\Pi^1_2$ consequences of arithmetical comprehension and related systems, $\Pi^1_2$-soundness ordinals, and the $\Pi^1_2$-Spectrum Conjecture. This is joint work with F. Pakhomov. Time and Place Talk at 3:00pm Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

This Week in Logic at CUNY

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

- - - - Monday, May 23, 2022 - - - -



- - - - Tuesday, May 24, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 24, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Laurence Kirby, Brooklyn College
The winding road to mathematical independence results for PA

Advances in understanding the incompleteness of PA in the 1970s and 80s built on the work of an earlier generation in the 1930s and 40s. This talk will offer historical and personal reflections on what was known, and what was not known, by both generations of logicians.




- - - - Wednesday, May 25, 2022 - - - -



- - - - Thursday, May 26, 2022 - - - -



- - - - Friday, May 27, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 27, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties: Part II

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.




Next Week in Logic at CUNY:

- - - - Monday, May 30, 2022 - - - -



- - - - Tuesday, May 31, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 31, 8pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Tin Lok Wong National University of Singapore




- - - - Wednesday, Jun 1, 2022 - - - -



- - - - Thursday, Jun 2, 2022 - - - -



- - - - Friday, Jun 3, 2022 - - - -



- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

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Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 25th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Tommaso Russo -- Walks on ordinals and scattered compact spaces I will present a construction of a scattered compact topological space that answered a question due to Wiesław Kubiś and Arkady Leiderman. The construction is contained in a joint paper with Petr Hájek, Jacopo Somaglia, and Stevo Todorčević. The purpose of the paper was actually to answer a problem in Banach space theory, but for the sake of the talk I will focus on the construction of the compact space and not mention Banach spaces at all. In the talk I will give a short introduction to Descriptive Topology in order to explain the setting and to motivate the construction of the example. Then I will explain how to use the combinatorics of the set of countable ordinals, in particular Todorčević's theory of walks on ordinals, for the construction of the example. P.Hájek, T.Russo, J.Somaglia, and S.Todorčević, An Asplund space with norming Markuševič basis that is not weakly compactly generated, https://doi.org/10.1016/j.aim.2021.108041 Adv. Math. 392 (2021), 108041. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Peter Holy
TITLE: Asymmetric Cut and Choose Games
DATE: 25 May 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.








Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu




(KGRC) Set Theory Research Seminar talks Tuesday, May 24 and WEDNESDAY, May 25

Kurt Godel Research Center
The KGRC welcomes as guests: David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21. Details for this talk will be announced later. Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC until May 31. Jonathan Cancino (host: Vera Fischer) visits the KGRC until May 20. James Mitchell (host: Vera Fischer) visits the KGRC from May 21 to May 28 and gives a talk on May 25 (see below). Yann Peresse (host: Serhii Bardyla) visits the KGRC from May 21 to May 28. Luke Elliott (host: Lyubomyr Zdomskyy) visits the KGRC from May 21 to May 28 and gives a talk on May 25, see below. Gunter Fuchs (host: Vera Fischer) visits the KGRC from June 12 to June 18 and gives a talk on June 14. Details for this talk will be announced later. Alessandro Vignati (host: Vera Fischer) visits the KGRC from June 30 to July 1 and gives a talk on June 30. Details for this talk will be announced later. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, May 24 "Inner Models, Determinacy, and Sealing" Sandra Müller (TU Wien) Inner model theory has been very successful in connecting determinacy axioms to the existence of inner models with large cardinals and other natural hypotheses. Recent results of Larson, Sargsyan, and Trang suggest that a Woodin limit of Woodin cardinals is a natural barrier for our current methods to prove these connections. One reason for this comes from Sealing, a generic absoluteness principle for the theory of the universally Baire sets of reals introduced by Woodin. Woodin showed in his famous Sealing Theorem that in the presence of a proper class of Woodin cardinals Sealing holds after collapsing a supercompact cardinal. I will outline the importance of Sealing and discuss a new and stationary-tower-free proof of Woodin's Sealing Theorem that is based on Sargsyan's and Trang's proof of Sealing from iterability. This is joint work with Grigor Sargsyan and Bartosz Wcisło. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Set Theory Research Seminar Kurt Gödel Research Center WEDNESDAY, May 25 (Please note the unusual day and time!) "Unindexed subshifts of finite type and a connecton to Thompsons groups" Luke Elliott (U of St Andrews, Scotland, UK) I will give a brief introduction to subshifts of finite type defined by finite directed graphs. In particular I will mention a category of "digaphs and foldings" introduced by Jim Belk, Collin Bleak, and Peter Cameron which is useful for studying these systems. I will then discuss my recent work in building an analogous category in which isomorphisms don't necessarily preserve indexing and path length. This category gives us both more flexible notions of (strong) shift equivalence and a connection to automorphisms of Thompsons groups. Time and Place (Please note the unusual day and time!) Talk at 11:30am in hybrid mode, in person as well as via Zoom: Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

Cross-Alps Logic Seminar (speaker: Alberto Marcone)

Cross-Alps Logic Seminar
On Friday 20.05.2022 at 16:00
Alberto Marcone (University of Udine)
will give a talk on
The transfinite Ramsey theorem

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] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.


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This Week in Logic at CUNY

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

- - - - Monday, May 16, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 16, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Mircea Dumitru (Bucharest)
Title: Modal Frame Incompleteness: An Account through Second Order Logic

Abstract: Propositional modal logic is usually viewed as a generalization and extension of propositional classical logic. The main argument of this paper is that a good case can be made that modal logic should be construed as a restricted form of second order classical logic. The paper makes use of the embedding of modal logic in second order logic and henceforth it goes on examining one aspect of this second order connection having to do with an incompleteness phenomenon. The leading concept is that modal incompleteness is to be explained as a kind of exemplification of standard order incompleteness. Moreover the modal incompleteness phenomenon is essentially rooted in the weaker expressive power of the language of sentential modal logic as compared to the stronger expressive power of the language of second order logic.




- - - - Tuesday, May 17, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 17, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Ken McAloon, Brooklyn College
E Pluribus Unum

Athena sprang forth full grown from the head of Zeus. Newton/Leibniz created Calculus. Galois created Galois Theory. Cantor created Set Theory. Boole created Boolean Algebra.

But Models of Peano Arithmetic doesn’t have a dramatic origin myth like that and took some 100 years to emerge as a discipline in itself - from Dedekind’s Second Order Axioms for Arithmetic (1863), through Frege’s Begriffsschrift (1879) and First Order Logic, through Godel’s Completeness and Incompleteness Theorems, through Skolem’s elegant construction of a non-standard model, through the War and après-guerre and on into the 1970s where the subject at last emerges as a discipline in itself. We’ll discuss the convergence of people and ideas from diverse fields like Model Theory, Set Theory, Recursion Theory, Proof Theory, Complexity Theory, … that led to the field we know and love today.





- - - - Wednesday, May 18, 2022 - - - -



- - - - Thursday, May 19, 2022 - - - -



- - - - Friday, May 20, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 20, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.




Next Week in Logic at CUNY:

- - - - Monday, May 23, 2022 - - - -



- - - - Tuesday, May 24, 2022 - - - -



- - - - Wednesday, May 25, 2022 - - - -



- - - - Thursday, May 26, 2022 - - - -



- - - - Friday, May 27, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 27, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties: Part II

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.



- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Laura Fontanella
TITLE: Representing ordinals in classical realizability
DATE: 18 May 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu



Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 18th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Uhrik -- Hadwiger's conjecture for infinite graphs Hadwiger's conjecture is one of the most famous unsolved problems in finite graph theory. I will talk about the infinite version of this conjecture and related results. Best, David

(KGRC) Set Theory Research Seminar talk Tuesday, May 17 and Logic Colloquium talk Thursday, May 19

Kurt Godel Research Center
The KGRC welcomes as guests: Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC until May 31. David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21. Details for the talk will be announced at a later time. Jonathan Cancino (host: Vera Fischer) visits the KGRC from May 16 to May 20. James Mitchell (host: Vera Fischer) visits the KGRC from May 21 to May 28 and gives a talk on May 25, 11:30am (please note the unusual time!). Details for the talk will be announced at a later time. Yann Peresse (host: Serhii Bardyla) visits the KGRC from May 21 to May 28. Luke Elliott (host: Lyubomyr Zdomskyy) visits the KGRC from May 21 to May 28. Alessandro Vignati (host: Vera Fischer) visits the KGRC from June 30 to July 1 and gives a talk on June 30. Details for the talk will be announced at a later time. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, May 17 "Patterns in the large cardinal hierarchy" Philipp Lücke (University of Bareclona) In my talk, I will present results showing that the existence of various well-known large cardinals can be characterized through the validity of strong extensions of the downward Löwenheim-Skolem theorem. These equivalences show that certain patterns recur throughout the large cardinal hierarchy. In particular, they show that strongly unfoldable cardinals, introduced by Villaveces in his model-theoretic investigations of models of set theory, relate to subtle cardinals, introduced by Kunen and Jensen in their studies of strong diamond principles, in the same way as supercompact cardinals relate to Vopěnka cardinals and strong cardinals relate to Woodin cardinals. This is joint work in progress with Joan Bagaria (Barcelona). Time and Place This talk will be given via Zoom. If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) * * * Logic Colloquium Kurt Gödel Research Center Thursday, May 19 "Axiomatizing Kaufmann Models of Arithmetic in Strong Logics" Corey Switzer (KGRC) A {\em Kaufmann model} of $\mathsf{PA}$ is an $\omega_1$-like, recursively saturated, rather classless model (these terms will be defined in the talk). Such models have been an important object of study in model theory of arithmetic and its environs since the 70's. Kaufmann models are natural counterexamples to several theorems about countable models of $\mathsf{PA}$ holding at the uncountable. Moreover they are a witness to incompactness at $\omega_1$ similar to an Aronszajn tree. The proof that Kaufmann models exist lies along a somewhat twisted road. Kaufmann showed that there are Kaufmann models under the combinatorial principle $\diamondsuit_{\omega_1}$ and, later, Shelah eliminated the use of $\diamondsuit_{\omega_1}$ by appealing to a forcing absoluteness argument involving the strong logic $L_{\omega_1, \omega}(Q)$ where $Q$ is the quantifier ``there exists uncountably many''. It remains an extremely interesting, if somewhat vague, question, attributed to Hodges, whether one can build a Kaufmann model ``by hand'' in $\mathsf{ZFC}$ without appealing to generic absoluteness. In this talk we will report on our recent progress in this area. Specifically we will consider the role that the strong logic $L_{\omega_1, \omega}(Q)$ plays in Kaufmann models and show that the statement ``Kaufmann models can be axiomatized by $L_{\omega_1, \omega}(Q)$'' is independent of $\mathsf{ZFC}$. Along the way we will discuss how Kaufmann models are affected by forcing and in particular show that it is independent of $\mathsf{ZFC}$ whether or not there is a Kaufmann model which can be ``killed" by forcing without collapsing $\omega_1$. Time and Place Talk at 3:00pm Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

TOMORROW: Vladimir Tkachuk at the Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
Lindelöf Σ-spaces in 2022 Speaker: Vladimir Tkachuk, Universidad Autónoma Metropolitana Date and Time: Friday, May 13, 2022 - 1:30pm to 3:00pm EDT (UTC -4) Location: https://zoom.us/j/92701726800 Abstract: This talk is a survey and an advertisement of the theory of Lindelöf Σ-spaces. We will present ten equivalent definitions of the Lindelöf Σ-property and a selection of results that have numerous applications in General Topology, Topological Algebra and C_p-theory. http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Cross-Alps Logic Seminar (speaker: Udayan B. Darji)

Cross-Alps Logic Seminar
On Friday 13.05.2022 at 16:00
Udayan B. Darji (University of Louisville)
will give a talk on
Descriptive complexity and local entropy

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 2017 'Mathematical logic: models, sets, computability'.



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UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Quick correction:  Tuesday's Models of Peano Arithmetic (MOPA) talk will take place at 10am (not 2pm). 

Sorry for the error,
Jonas


This Week in Logic at CUNY:

- - - - Monday, May 9, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 9, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Julian Schlöder (UConn).
Title: Neo-Pragmatism about Truth

Abstract: Deflationists about truth hold that the function of the truth predicate is to enable us to make certain assertions we could not otherwise make. Pragmatists claim that the utility of negation lies in its role in registering incompatibility. The pragmatist insight about negation has been successfully incorporated into bilateral theories of content, which take the meaning of negation to be inferentially explained in terms of the speech act of rejection. One can implement the deflationist insight in the pragmatist’s theory of content by taking the meaning of the truth predicate to be explained by its inferential relation to assertion. There are two upshots. First, a new diagnosis of the Liar, Revenges and attendant paradoxes: the paradoxes require that truth rules preserve evidence, but they only preserve commitment. Second, one straightforwardly obtains axiomatisations of several supervaluational hierarchies, answering the question of how such theories are to be naturally axiomatised. This is joint work with Luca Incurvati (Amsterdam).





- - - - Tuesday, May 10, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 10, 10am
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Saeed Salehi, University of Tabriz
ω-Consistency: Gödel’s “much weaker” notion of soundness

As the history goes, and was confirmed recently [vP20], Gödel first proved his first incompleteness theorem [G31] for sound theories (that extend Principia Mathematica). Later he weakened the soundness condition to “ℵ0-consistency”, which later evolved to “ω-consistency”. This condition was needed for irrefutability of (what is now called) Gödelian sentences; the simple consistency of a theory suffices for the unprovability of such sentences. Gödel already notes in [G31] that a necessary and sufficient condition for the independence of Gödelian sentences of T is just a bit more than the simple consistency of T: the consistency of T with ConT, the consistency statement of T.
In this talk, we ask the following questions and attempt at answering them, at least partially.

  1. Why on earth Gödel [G31] had to introduce this rather strange notion?
  2. Does it have any applications in other areas of logic, arithmetical theories, or mathematics?
  3. What was Gödel’s reason that ω-consistency is “much weaker” than soundness? He does prove in [G31] that consistency is weaker (if not much weaker) than ω-consistency; but never mentions a proof or even a hint as to why soundness is (much) stronger than ω-consistency!
  4. Other than those historical and philosophical questions, is this a useful notion worthy of further study?
We will also review some properties of ω-consistency in the talk.
References:
  • [G31]   Kurt Gödel (1931); “On formally undecidable propositions of Principia Mathematica and related systems I”, in: S. Feferman, et al. (eds.), Kurt Gödel: Collected Works, Vol. I: Publications 1929–1936, Oxford University Press, 1986, pp. 135–152.
  • [vP20]   Jan von Plato (2020); Can Mathematics Be Proved Consistent? Gödel’s Shorthand Notes & Lectures on Incompleteness, Springer.
    Reviewed in the zbMATH Open at https://zbmath.org/1466.03001




- - - - Wednesday, May 11, 2022 - - - -

Tutorial: Categorical Semantics of Entropy
Wednesday 11 May 2022, 13:00–16:30 Eastern Time, Room 5209 at the CUNY Graduate Center and via Zoom. Organized by John Terilla. 
To attend, register here.




- - - - Thursday, May 12, 2022 - - - -



- - - - Friday, May 13, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 13, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrew Brooke-Taylor University of Leeds


CONFERENCE: Categorical Semantics of Entropy
There will be a workshop on the categorical semantics of entropy at the CUNY Grad Center in Manhattan on Friday May 13th.
John Baez uc Riverside; Centre for Quantum Technologies; Topos Institute 
Tai-Danae Bradley The Master's University; Sandbox AQ
Owen Lynch Utrecht University
Tom Mainiero Rutgers New High Energy Theory Center
Arthur Parzygnat Institut des Hautes Études Scientifiques
David Spivak MIT and the Topos Instiftute
Note: There is a related tutorial taking place on May 11 (see above).



Next Week in Logic at CUNY:

- - - - Monday, May 16, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 16, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Mircea Dumitru (Bucharest)
Title: Modal Frame Incompleteness: An Account through Second Order Logic

Abstract: Propositional modal logic is usually viewed as a generalization and extension of propositional classical logic. The main argument of this paper is that a good case can be made that modal logic should be construed as a restricted form of second order classical logic. The paper makes use of the embedding of modal logic in second order logic and henceforth it goes on examining one aspect of this second order connection having to do with an incompleteness phenomenon. The leading concept is that modal incompleteness is to be explained as a kind of exemplification of standard order incompleteness. Moreover the modal incompleteness phenomenon is essentially rooted in the weaker expressive power of the language of sentential modal logic as compared to the stronger expressive power of the language of second order logic.




- - - - Tuesday, May 17, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 17, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Ken McAloon, Brooklyn College
E Pluribus Unum

Athena sprang forth full grown from the head of Zeus. Newton/Leibniz created Calculus. Galois created Galois Theory. Cantor created Set Theory. Boole created Boolean Algebra.

But Models of Peano Arithmetic doesn’t have a dramatic origin myth like that and took some 100 years to emerge as a discipline in itself - from Dedekind’s Second Order Axioms for Arithmetic (1863), through Frege’s Begriffsschrift (1879) and First Order Logic, through Godel’s Completeness and Incompleteness Theorems, through Skolem’s elegant construction of a non-standard model, through the War and après-guerre and on into the 1970s where the subject at last emerges as a discipline in itself. We’ll discuss the convergence of people and ideas from diverse fields like Model Theory, Set Theory, Recursion Theory, Proof Theory, Complexity Theory, … that led to the field we know and love today.





- - - - Wednesday, May 18, 2022 - - - -



- - - - Thursday, May 19, 2022 - - - -



- - - - Friday, May 20, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 20, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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This Week in Logic at CUNY

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

- - - - Monday, May 9, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 9, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Julian Schlöder (UConn).
Title: Neo-Pragmatism about Truth

Abstract: Deflationists about truth hold that the function of the truth predicate is to enable us to make certain assertions we could not otherwise make. Pragmatists claim that the utility of negation lies in its role in registering incompatibility. The pragmatist insight about negation has been successfully incorporated into bilateral theories of content, which take the meaning of negation to be inferentially explained in terms of the speech act of rejection. One can implement the deflationist insight in the pragmatist’s theory of content by taking the meaning of the truth predicate to be explained by its inferential relation to assertion. There are two upshots. First, a new diagnosis of the Liar, Revenges and attendant paradoxes: the paradoxes require that truth rules preserve evidence, but they only preserve commitment. Second, one straightforwardly obtains axiomatisations of several supervaluational hierarchies, answering the question of how such theories are to be naturally axiomatised. This is joint work with Luca Incurvati (Amsterdam).





- - - - Tuesday, May 10, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 10, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Saeed Salehi, University of Tabriz
ω-Consistency: Gödel’s “much weaker” notion of soundness

As the history goes, and was confirmed recently [vP20], Gödel first proved his first incompleteness theorem [G31] for sound theories (that extend Principia Mathematica). Later he weakened the soundness condition to “ℵ0-consistency”, which later evolved to “ω-consistency”. This condition was needed for irrefutability of (what is now called) Gödelian sentences; the simple consistency of a theory suffices for the unprovability of such sentences. Gödel already notes in [G31] that a necessary and sufficient condition for the independence of Gödelian sentences of T is just a bit more than the simple consistency of T: the consistency of T with ConT, the consistency statement of T.
In this talk, we ask the following questions and attempt at answering them, at least partially.

  1. Why on earth Gödel [G31] had to introduce this rather strange notion?
  2. Does it have any applications in other areas of logic, arithmetical theories, or mathematics?
  3. What was Gödel’s reason that ω-consistency is “much weaker” than soundness? He does prove in [G31] that consistency is weaker (if not much weaker) than ω-consistency; but never mentions a proof or even a hint as to why soundness is (much) stronger than ω-consistency!
  4. Other than those historical and philosophical questions, is this a useful notion worthy of further study?
We will also review some properties of ω-consistency in the talk.
References:
  • [G31]   Kurt Gödel (1931); “On formally undecidable propositions of Principia Mathematica and related systems I”, in: S. Feferman, et al. (eds.), Kurt Gödel: Collected Works, Vol. I: Publications 1929–1936, Oxford University Press, 1986, pp. 135–152.
  • [vP20]   Jan von Plato (2020); Can Mathematics Be Proved Consistent? Gödel’s Shorthand Notes & Lectures on Incompleteness, Springer.
    Reviewed in the zbMATH Open at https://zbmath.org/1466.03001




- - - - Wednesday, May 11, 2022 - - - -

Tutorial: Categorical Semantics of Entropy
Wednesday 11 May 2022, 13:00–16:30 Eastern Time, Room 5209 at the CUNY Graduate Center and via Zoom. Organized by John Terilla. 
To attend, register here.




- - - - Thursday, May 12, 2022 - - - -



- - - - Friday, May 13, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 13, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrew Brooke-Taylor University of Leeds


CONFERENCE: Categorical Semantics of Entropy
There will be a workshop on the categorical semantics of entropy at the CUNY Grad Center in Manhattan on Friday May 13th.
John Baez uc Riverside; Centre for Quantum Technologies; Topos Institute 
Tai-Danae Bradley The Master's University; Sandbox AQ
Owen Lynch Utrecht University
Tom Mainiero Rutgers New High Energy Theory Center
Arthur Parzygnat Institut des Hautes Études Scientifiques
David Spivak MIT and the Topos Instiftute
Note: There is a related tutorial taking place on May 11 (see above).



Next Week in Logic at CUNY:

- - - - Monday, May 16, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 16, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Mircea Dumitru (Bucharest)
Title: Modal Frame Incompleteness: An Account through Second Order Logic

Abstract: Propositional modal logic is usually viewed as a generalization and extension of propositional classical logic. The main argument of this paper is that a good case can be made that modal logic should be construed as a restricted form of second order classical logic. The paper makes use of the embedding of modal logic in second order logic and henceforth it goes on examining one aspect of this second order connection having to do with an incompleteness phenomenon. The leading concept is that modal incompleteness is to be explained as a kind of exemplification of standard order incompleteness. Moreover the modal incompleteness phenomenon is essentially rooted in the weaker expressive power of the language of sentential modal logic as compared to the stronger expressive power of the language of second order logic.




- - - - Tuesday, May 17, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 17, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Ken McAloon, Brooklyn College
E Pluribus Unum

Athena sprang forth full grown from the head of Zeus. Newton/Leibniz created Calculus. Galois created Galois Theory. Cantor created Set Theory. Boole created Boolean Algebra.

But Models of Peano Arithmetic doesn’t have a dramatic origin myth like that and took some 100 years to emerge as a discipline in itself - from Dedekind’s Second Order Axioms for Arithmetic (1863), through Frege’s Begriffsschrift (1879) and First Order Logic, through Godel’s Completeness and Incompleteness Theorems, through Skolem’s elegant construction of a non-standard model, through the War and après-guerre and on into the 1970s where the subject at last emerges as a discipline in itself. We’ll discuss the convergence of people and ideas from diverse fields like Model Theory, Set Theory, Recursion Theory, Proof Theory, Complexity Theory, … that led to the field we know and love today.





- - - - Wednesday, May 18, 2022 - - - -



- - - - Thursday, May 19, 2022 - - - -



- - - - Friday, May 20, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 20, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 11th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- Ultrafilters in the Miller model We will sketch a proof that in the Miller's model I-ultrafilters are dense in the Rudin-Blass ordering for any analytic tall p-ideal I. We will finish with some remarks to a theorem of C. Laflamme and J. P. Zhu, and some questions on cardinal invariants related to the existence of I-ultrafilters. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Sandra Müller
TITLE: Inner Models, Determinacy, and Sealing
DATE: 11 May 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.





Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


(KGRC) Wednesday, May 11: Inaugural Lecture of Matthias Aschenbrenner

Kurt Godel Research Center
The KGRC welcomes as guests: Miguel Antonio Cardona Montoya (host: Vera Fischer) visits the KGRC until May 6. Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC until May 31. David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21. Details for the talk will be announced at a later time. James Mitchell (host: Vera Fischer) visits the KGRC from May 21 to May 28. Yann Peresse (host: Serhii Bardyla) visits the KGRC from May 21 to May 28. Luke Elliott (host: Lyubomyr Zdomskyy) visits the KGRC from May 21 to May 28. * * * Mathematisches Kolloquium Faculty of Mathematics Wednesday, May 11 Inaugural Lecture: "Hardy’s dream" Matthias Aschenbrenner (KGRC) I will introduce an algebraic approach to asymptotic analysis, which goes back to G. H. Hardy but has its roots in the 19th century, and which has found uses in real analytic geometry and dynamical systems, computer algebra, ergodic theory, and various other fields of mathematics. In the last few years, we have obtained some decisive results on solving systems of algebraic differential equations in this setting, leading to rich classes of non-oscillating differentiable real-valued functions which partially substantiate “Hardy’s dream” (Ecalle). These results are obtained through a fruitful interplay between analysis, algebra, and logic, which I will outline in this talk. (No prior knowledge of mathematical logic will be assumed.) Time and Place Coffee at 3:45pm Talk at 4:15pm in hybrid mode, in person as well as via Zoom followed by refreshments Universität Wien Fakultät für Mathematik 12th floor Sky Lounge Oskar-Morgenstern-Platz 1 1090 Wien Zoom link for Inaugural Lecture: https://univienna.zoom.us/j/65619931234?pwd=WTdKV1Z4NGxBeklkT0RtNzltZEhBUT09 (See also PDF attached to this message.)
View attachment

Mirna Dzamonja at the Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
Morass-generic structures Speaker: Mirna Dzamonja, IRIF - Centre national de la recherche scientifique (CNRS) - Université deParis Date and Time: Friday, May 6, 2022 - 1:30pm to 3:00pm EDT (UTC -4) Location: https://zoom.us/j/92701726800 Abstract: We discuss a joint work with Wiesław Kubiś on a specific way of constructing structures of size ℵ1 using finite approximations, namely by organising the approximations along a simplified morass. We demonstrate a connection with Fraïssé limits and show that the naturally obtained structure of size ℵ1 is homogeneous. Moreover, this is preserved under expansions, which leads us to a partial answer to a question of Bassi and Zucker. We give some examples of interesting structures constructed, such as the antimetric space of size ℵ1. Finally, we comment on the situation when one Cohen real is added. http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

This Week in Logic at CUNY

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

- - - - Monday, May 2, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 2, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Elia Zardini (Madrid)

Abstract: I’ll first propose an interpretation of the multiplicative/additive distinction among operators arising in a logical framework lacking the structural property of contraction (focusing mostly on the quantifiers): multiplicative operators represent interaction among their operands (with universal quantification representing totality and particular quantification representing dependence) whereas additive operators represent selection (with universal quantification representing choice and particular quantification representing chance). I’ll then argue that reflection on the behaviour of natural-language determiners points towards a very natural working hypothesis that associates: multiplicative universal affirmative with ‘every’; multiplicative particular affirmative with ‘some’; additive universal affirmative with ‘any’; additive particular affirmative with ‘a’. I’ll illustrate the fruitfulness of this hypothesis with four examples, from the epistemic, normative, attitudinal and stative domains respectively.



- - - - Tuesday, May 3, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 3, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Dino Rossegger, UC Berkeley and TU Wien
The structural complexity of models of PA

The Scott rank of a countable structure is the least ordinal  such that all automorphism orbits of the structure are definable by infinitary  formulas. Montalbán showed that the Scott rank of a structure is a robust measure of the structural and computational complexity of a structure by showing that various different measures are equivalent. For example, a structure has Scott rank  if and only if it has a  Scott sentence if and only if it is uniformly  categorical if and only if all its automorphism orbits are  infinitary definable.

In this talk we present results on the Scott rank of non-standard models of Peano arithmetic. We show that non-standard models of PA have Scott rank at least , but, other than that, there are no limits to their complexity. Given a completion  of  we give a reduction via bi-interpretability of the class of linear orders to the models of . This allows us to exhibit models of  of Scott rank  for every . In particular, every completion of  has models of high Scott rank.

This is joint work with Antonio Montalbán.



- - - - Wednesday, May 4, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Gershom Bazerman, Arista Networks.

Date and Time:     Wednesday May 4, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Classes of Closed Monoidal Functors which Admit Infinite Traversals.



- - - - Thursday, May 5, 2022 - - - -



- - - - Friday, May 6, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 6, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
James Holland Rutgers University

Weak Indestructibility and Reflection

Assuming multiple of strong cardinals, there are lots of cardinals with small degrees of strength (i.e.  that are +2-strong). We can calculate the consistency strength of these all cardinal's small degrees of strength being weakly indestructible using forcing and core model techniques in a way similar to Apter and Sargsyan's previous work. This yields some easy relations between indestructibility and Woodin cardinals, and also generalizes easily to supercompacts. I will give a proof sketches of these results.



Logic Workshop
CUNY Graduate Center, GC Room 6495
Friday, May 6, 2:00-3:30pm
Hybrid - The seminar will take place virtually at 2:00pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Alexei Miasnikov, Stevens Institute of Technology
Rich algebraic structures and weak second order logic

“What can one describe by first-order formulas in a given algebraic structure A?” - is an old and interesting question. Of course, this depends on the structure A. For example, in a free group only cyclic subgroups (and the group itself) are definable in the first-order logic, but in a free monoid of finite rank any finitely generated submonoid is definable. An algebraic structure A is called rich if the first-order logic in A is equivalent to the weak second order logic. Surprisingly, there are a lot of interesting groups, rings, semigroups, etc., which are rich. I will discuss some of them and then describe various algebraic, geometric, and algorithmic properties that are first-order definable in rich structures and apply these to some open problems. Weak second order logic can be introduced into algebraic structures in different ways: via HF-logic, or list superstructures over A, or computably enumerable infinite disjunctions and conjunctions, or via finite binary predicates, etc. I will describe a particular form of this logic which is especially convenient to use in algebra and show how to effectively translate such weak second order formulas into the equivalent first-order ones in the case of a rich structure A.



Next Week in Logic at CUNY:

- - - - Monday, May 9, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 9, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Julian Schlöder (UConn).
Title: Neo-Pragmatism about Truth

Abstract: Deflationists about truth hold that the function of the truth predicate is to enable us to make certain assertions we could not otherwise make. Pragmatists claim that the utility of negation lies in its role in registering incompatibility. The pragmatist insight about negation has been successfully incorporated into bilateral theories of content, which take the meaning of negation to be inferentially explained in terms of the speech act of rejection. One can implement the deflationist insight in the pragmatist’s theory of content by taking the meaning of the truth predicate to be explained by its inferential relation to assertion. There are two upshots. First, a new diagnosis of the Liar, Revenges and attendant paradoxes: the paradoxes require that truth rules preserve evidence, but they only preserve commitment. Second, one straightforwardly obtains axiomatisations of several supervaluational hierarchies, answering the question of how such theories are to be naturally axiomatised. This is joint work with Luca Incurvati (Amsterdam).





- - - - Tuesday, May 10, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 10, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Saeed Salehi, University of Tabriz
ω-Consistency: Gödel’s “much weaker” notion of soundness

As the history goes, and was confirmed recently [vP20], Gödel first proved his first incompleteness theorem [G31] for sound theories (that extend Principia Mathematica). Later he weakened the soundness condition to “ℵ0-consistency”, which later evolved to “ω-consistency”. This condition was needed for irrefutability of (what is now called) Gödelian sentences; the simple consistency of a theory suffices for the unprovability of such sentences. Gödel already notes in [G31] that a necessary and sufficient condition for the independence of Gödelian sentences of T is just a bit more than the simple consistency of T: the consistency of T with ConT, the consistency statement of T.
In this talk, we ask the following questions and attempt at answering them, at least partially.

  1. Why on earth Gödel [G31] had to introduce this rather strange notion?
  2. Does it have any applications in other areas of logic, arithmetical theories, or mathematics?
  3. What was Gödel’s reason that ω-consistency is “much weaker” than soundness? He does prove in [G31] that consistency is weaker (if not much weaker) than ω-consistency; but never mentions a proof or even a hint as to why soundness is (much) stronger than ω-consistency!
  4. Other than those historical and philosophical questions, is this a useful notion worthy of further study?
We will also review some properties of ω-consistency in the talk.
References:
  • [G31]   Kurt Gödel (1931); “On formally undecidable propositions of Principia Mathematica and related systems I”, in: S. Feferman, et al. (eds.), Kurt Gödel: Collected Works, Vol. I: Publications 1929–1936, Oxford University Press, 1986, pp. 135–152.
  • [vP20]   Jan von Plato (2020); Can Mathematics Be Proved Consistent? Gödel’s Shorthand Notes & Lectures on Incompleteness, Springer.
    Reviewed in the zbMATH Open at https://zbmath.org/1466.03001




- - - - Wednesday, May 11, 2022 - - - -

Tutorial: Categorical Semantics of Entropy
Wednesday 11 May 2022, 13:00–16:30 Eastern Time, Room 5209 at the CUNY Graduate Center and via Zoom. Organized by John Terilla. 
To attend, register here.




- - - - Thursday, May 12, 2022 - - - -



- - - - Friday, May 13, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 13, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrew Brooke-Taylor University of Leeds


CONFERENCE: Categorical Semantics of Entropy
There will be a workshop on the categorical semantics of entropy at the CUNY Grad Center in Manhattan on Friday May 13th.
John Baez uc Riverside; Centre for Quantum Technologies; Topos Institute 
Tai-Danae Bradley The Master's University; Sandbox AQ
Owen Lynch Utrecht University
Tom Mainiero Rutgers New High Energy Theory Center
Arthur Parzygnat Institut des Hautes Études Scientifiques
David Spivak MIT and the Topos Instiftute
Note: There is a related tutorial taking place on May 11 (see above).


- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 4th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Some simple applications of set theory to the study of projective and injective objects in various categories Projective and injective objects are of central interest in category theory and homological algebra. We will survey a few interesting results applying set-theoretic ideas to the study of such objects in the categories of compact Hausdorff spaces, Banach spaces, and pro-abelian groups. Time permitting, we will also discuss some recent applications of set theory to the newly developed "condensed mathematics" of Clausen and Scholze. Everything will be presented at a fairly basic level; no significant prior knowledge of either set theory or category theory/homological algebra will be required of the audience. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All,
For the next seminar session, on May 4, please use the following link, instead of the usual one.




Apologies for the inconvenience.
Best regards,
Joan Bagaria



El 27 abr 2022, a les 18:10, Joan Bagaria <joan.bagaria@icrea.cat> va escriure:



El 27 gen 2022, a les 21:17, Joan Bagaria <joan.bagaria@icrea.cat> va escriure:

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Will Boney
TITLE: Compactness of strong logics and large cardinals
DATE: 4 May 2022
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.


<BCNSETS2022-2-Boney.pdf>

Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Barcelona Set Theory Seminar

Barcelona Logic Seminar


El 27 gen 2022, a les 21:17, Joan Bagaria <joan.bagaria@icrea.cat> va escriure:

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Will Boney
TITLE: Compactness of strong logics and large cardinals
DATE: 4 May 2022
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


(KGRC) Set Theory Seminar talk Tuesday, May 3

Kurt Godel Research Center
The KGRC welcomes as guests: Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC from May 2 to May 31. Miguel Antonio Cardona Montoya (host: Vera Fischer) visits the KGRC from May 2 to May 6 and gives a talk (see below). David Schrittesser (host: Vera Fischer) visits the KGRC from May 2 to August 31 and gives a talk on June 21. * * * For a recent session in the Set Theory Research Seminar, video has been recorded. So if you missed it or want to rewatch it, here it is: Wolfgang Wohofsky, "Fresh function spectra" https://univienna.zoom.us/rec/share/vwFTPqrhTaAiFQ69Wn2JQF_nKulP0jvSRK8W3BvInrAyigDfZjMjeV67YOPedR5X.D2QNfwj0OkvjgZID Passcode H5#My6LX * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, May 3 "On the cardinal characteristics associated with \varepsilon" Miguel Antonio Cardona Montoya (TU Wien) Let $\varepsilon$ be the $\sigma$-ideal generated by closed measure zero sets of reals. We prove that, for $\varepsilon$, their associated cardinal characteristics (i.e. additivity, covering, uniformity and cofinality) are pairwise different. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

XIX Latin American Symposium of Mathematical Logic (SLALM), Costa Rica, July 26-30

Conference
Estimado miembro de la comunidad matemática, Fecha límite extendida para recepción de charlas y pósters: 1 de Mayo del 2022. Le agradeceríamos difundir a sus colegas, estudiantes y a su Sociedad Matemática local, el anuncio del XIX Simposio Latino Americano de Lógica Matemática, el cual tendrá lugar en la, en la ciudad de San José, Costa Rica, del martes 26 al sábado 30 de Julio del 2022. Esta conferencia será presencial. Podrá encontrar más información en el siguiente vínculo: Sitio Oficial. Además, queremos notar las fechas límites: Inscripción temprana: antes 22 de abril de 2022 Inscripción: antes 30 de junio de 2022 Recepción de charlas contribuidas y pósters: 1° de Mayo, 2022 Comunicación de aceptación-rechazo a los autores: antes 16 de mayo de 2022 Cordialmente, Comité Organizador *********************************************************************************************************************************** Extended deadline for contributed talks and posters: May 1st, 2022 Dear member of the mathematical community, We would be very grateful if you could share with your colleagues, students, and you local Mathematical Society the announcement of the XIX Latin American Symposium of Mathematical Logic (SLALM), which will be held at the Universidad de Costa Rica, in the city of San José, Costa Rica, from Friday July 26th to Saturday 20th of December, 2022. You will find more information on the following link: Official website SLALM Plus, we would like to point out the following important deadlines, Early registration April 22nd, 2022 Registration: June 30th, 2022 Contributed talks: May 1st, 2022 Communication of acceptance for contributed talks: May 16th, 2022 Sincerely, Organizing Committee
Link to more info

European Set Theory Conference 2022 - second announcement

Cross-Alps Logic Seminar
EUROPEAN SET THEORY CONFERENCE 2022
August 29th-September 2nd, 2022
Turin, Italy

This is the second announcement concerning the ESTC2022. In particular, please notice that
  • The deadline for submitting an abstract is approaching (next Saturday!): if you plan to give a contributed talk, please apply here.
  • Various forms of financial support for young researchers are available. We encourage all interested students and young post-docs to apply as soon as possible.
Please share this announcement with all people who might be interested in the event (more information below or on our website).

We are looking forward to welcoming you in Turin!
Luca Motto Ros (on behalf of the organizers)

-----------------------------------------------

IMPORTANT DEADLINES:

30/04/2022: Abstract submission for contributed talks
30/06/2022: Early registration with reduced fee
22/08/2022: Registration


MORE ON THE CONFERENCE:

The European Set Theory Conferences is a series of biannual meetings coordinated by the European Set Theory Society (ESTS). This year's edition is organized by the Department of Mathematics of the University of Turin and ESTS, in partnership with the Clay Mathematics Institute. It is the most important conference in set theory, and gathers the worldwide leaders in the field as well as many young researchers. During the event, the prestigious Hausdorff medal will be awarded for the most influential work in set theory published in the preceding five years. There will also be a special session in honor of Boban Veličković's 60th birthday.

Invited speakers

- Jeffrey Bergfalk (University of Vienna)
- Filippo Calderoni (University of Illinois Chicago)
- Natasha Dobrinen (University of Denver)
- Osvaldo Guzmán (Universidad Nacional Autónoma de México)
- Joel Hamkins (University of Notre Dame)
- Chris Lambie-Hanson (Czech Academy of Sciences)
- Martino Lupini (Victoria University of Wellington)
- Julien Melleray (Université de Lyon)
- Andrew Marks (University of California, Los Angeles)
- Sandra Müller (TU Wien)
- Saharon Shelah (Hebrew University of Jerusalem)
- Stevo Todorčević (University of Toronto and Centre national de la recherche scientifique)
- Jouko Väänänen (University of Helsinki)
- Zoltán Vidnyánsky (California Institute of Technology)
- Trevor Wilson (Miami University, Oxford Ohio)

Tutorials

- Yair Hayut (Hebrew University of Jerusalem)
- Grigor Sargsyan (Polish Academy of Sciences)

Boban Veličković's 60th Birthday Celebration

- Laura Fontanella (Université Paris-Est Créteil)
- Rahman Mohammadpour (TU Wien)
- Giorgio Venturi (University of Campinas)
- Matteo Viale (University of Turin)

Scientific committee

Joan Bagaria (chair), Matthew Foreman, Moti Gitik, Péter Komjáth, Piotr Koszmider, Heike Mildenberger, Luca Motto Ros, John Steel

Local organizing committee

Alessandro Andretta, Raphaël Carroy, Luca Motto Ros, Gianluca Paolini, Francesco Parente, Salvatore Scamperti, Matteo Viale

--
Luca Motto Ros
Università degli Studi di Torino
Dipartimento di Matematica
via Carlo Alberto, 10 - 10123 Torino, Italy

office phone: (+39) 011 670 2892
fax: (+39) 011 670 2878

Matteo Viale at the Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
The (Absolute) Model Companionship Spectrum of a mathematical theory and the Continuum problem Speaker: Matteo Viale, University of Torino and University of Turin Date and Time: Friday, April 29, 2022 - 1:30pm to 3:00pm Location: https://zoom.us/j/92701726800 Abstract: We introduce a classification tool for mathematical theories based on Robinson's notion of model companionship; roughly the idea is to attach to a mathematical theory T those signatures L such that T as axiomatized in L admits a(n absolute) model companion. To do so we also introduce a slight strengthening of model companionship (absolute model companionship - AMC) which characterize those model companionable L-theories T whose model companion is axiomatized by the Π2-sentences for L which are consistent with the universal theory of any L-model of T. We use the above to analyze set theory, and we show that the above classification tools can be used to extract (surprising?) information on the continuum problem. http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar To unsubscribe, send an email to SET-THEORY-FIELDS-L-signoff-request@LISTSERV.UTORONTO.CA

This Week in Logic at CUNY

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

- - - - Monday, Apr 25, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 25, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Tore Fjetland Øgaard (Bergen).
Title: Logical Suppression Anew

Abstract: Val Plumwood and Richard Sylvan argued from their joint paper The Semantics of First Degree Entailment and onward that the variable sharing property is but a mere consequence of a good entailment relation; indeed they viewed it as a mere negative test of adequacy of such a relation, the property itself being a rather philosophically barren concept. Such a relation is rather to be analyzed as a sufficiency relation free of any form of premise suppression. Suppression of premises, therefore, gained center stage. Despite this, however, no serious attempt was ever made at analyzing the concept. A first rigorous analysis of their notion of suppression was given in Farewell to Suppression-Freedom. Therein it was shown that Plumwood and Sylvan’s notion of suppression is in fact properly weaker than variable sharing. I will in the current talk explore ways of strengthening the suppression criterion. One plausible way of doing so, I will argue, yields a principle equivalent to the standard variable sharing property. I hope to show, then, that the notion of suppression is not as unfruitful as I previously made it out to be.



- - - - Tuesday, Apr 26, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 26, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Michał Godziszewski, University of Vienna
Modal Quantifiers, Potential Infinity, and Yablo sequences

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




- - - - Wednesday, Apr 27, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Alex Sorokin, Northeastern University.

Date and Time:     Wednesday April 27, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     The defect of a profunctor.


Abstract: In the mid 1960s Auslander introduced a notion of the defect of a finitely presented functor on a module category. In 2021 Martsinkovsky generalized it to arbitrary additive functors. In this talk I will show how to define a defect of any enriched functor with a codomain a cosmos. Under mild assumptions, the covariant (contravariant) defect functor turns out to be a left covariant (right contravariant) adjoint to the covariant (contravariant) Yoneda embedding. Both defects can be defined for any profunctor enriched in a cosmos V. They happen to be adjoints to the embeddings of V-Cat in V-Prof. Moreover, the Isbell duals of a profunctor are completely determined by the profunctor's covariant and contravariant defects. These results are based on applications of the Tensor-Hom-Cotensor adjunctions and the (co)end calculus.



- - - - Thursday, Apr 28, 2022 - - - -



- - - - Friday, Apr 29, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 29, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass University of Michigan
Do these ultrafilters exist, II: not Tukey top

This is the second of two talks devoted to two properties of ultrafilters (non-principal, on omega) for which the question 'Do such ultrafilters exist?' is open. In this talk, I'll discuss the property of not being at the top of the Tukey ordering (of ultrafilters on omega). I'll start with the definition of the Tukey ordering, and I'll give an example of an ultrafilter that is 'Tukey top'. It's consistent with ZFC that some ultrafilters are not Tukey top. The examples and the combinatorial characterizations involved here are remarkably similar but not identical to examples and the characterization from the previous talk. That observation suggests some conjectures, one of which I'll disprove if there's enough time.


Next Week in Logic at CUNY:

- - - - Monday, May 2, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 2, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Elia Zardini (Madrid)



- - - - Tuesday, May 3, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 3, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Dino Rossegger, UC Berkeley and TU Wien
The structural complexity of models of PA

The Scott rank of a countable structure is the least ordinal  such that all automorphism orbits of the structure are definable by infinitary  formulas. Montalbán showed that the Scott rank of a structure is a robust measure of the structural and computational complexity of a structure by showing that various different measures are equivalent. For example, a structure has Scott rank  if and only if it has a  Scott sentence if and only if it is uniformly  categorical if and only if all its automorphism orbits are  infinitary definable.

In this talk we present results on the Scott rank of non-standard models of Peano arithmetic. We show that non-standard models of PA have Scott rank at least , but, other than that, there are no limits to their complexity. Given a completion  of  we give a reduction via bi-interpretability of the class of linear orders to the models of . This allows us to exhibit models of  of Scott rank  for every . In particular, every completion of  has models of high Scott rank.

This is joint work with Antonio Montalbán.



- - - - Wednesday, May 4, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Gershom Bazerman, Arista Networks.

Date and Time:     Wednesday May 4, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Classes of Closed Monoidal Functors which Admit Infinite Traversals.



- - - - Thursday, May 5, 2022 - - - -



- - - - Friday, May 6, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 6, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
James Holland Rutgers University
TBA


- - - - 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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Kacper Kucharski, Using elementary submodels in topology (continuation)

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 26.04.2022, at 13.15, room 403 Speaker: Kacper Kucharski, (MIM UW) Title: Using elementary submodels in topology (continuation) Abstact: "The talk will be focused on presenting so-called reflection results e.g., Dow's theorem: every nonmetrizable compact Hausdorff space contains a nonmetrizable subspace of cardinality ω_1" Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 27th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Rahman Mohammadpour -- How to specialise a tree with smaller approximations A tree T of height $\kappa^+$ is called special if it is $\kappa$-colorable. The natural forcing to generically specialise a branchless tree of height $\kappa^+$ uses partial specialising functions of size less than $\kappa$. The chain condition of the post has a strong correlation with a particular compactness property. By a classical result due to Baumgartner, Malitz, and Reinhardt, there is a ccc forcing notion that generically specialises a branchless tree of height $\omega_1$, as that compactness property coincides with the property of being branchless when the height of the tree is $\omega_1$. But when the height is beyond $\omega_1$, i.e., $\kappa$ is uncountable, there might be, e.g. in the constructible universe, branchless trees that are not specialisable at all. Another negative aspect of the specialising poset is its dependence on cardinal arithmetic. For example, one cannot use it to generically specialise a tree of height $\omega_2$ without collapsing the continuum onto $\omega_1$. I will review some classical and known results on the above subjects. In particular, the connection between the chain condition of the specialising poset, the cardinal arithmetic, and a compactness property. I will then show how to use models, under appropriate circumstances, as side conditions to arrange specialisation with smaller approximations in the forcing conditions. I shall first focus on the simplest case, say trees of height $\omega_2$, and hope that I give enough details of the proofs. If times permits, I will discuss a similar problem for taller trees. Best, David

TOMORROW: Asger Törnquist at 13:30 EDT

Set Theory Seminar at the Fields Institute
Toronto Set Theory Seminar @ Fields Institute ---------------------------------------------- Friday April 22, 13:30 -- 14:30 EDT (UTC -4) Asger Törnquist (University of Copenhagen) Title: The mathematics of a model of the mind in psychology. Abstract: Jens Mammen, a psychologist, has proposed a model of the human mind based on the idea that the brain organizes objects in the world into two kinds of general categories: Broad categories, which he called "sense categories", and categories of special, distinguished objects (or people), which he called "choice categories". From a mathematical point of view, it is interesting that Mammen formulated his model of the mind axiomatically, based on the notion of a topological space. The objects in the universe are modelled by the points in a topological space (U,S), where the (broad) sense categories are modelled by open sets in the topology S. The choice categories forms an additional collection of subsets of the universe, C, that together with the topology must adhere to certain axioms. The triple (U,S,C) is called a "Mammen space" (a term that I introduced). Several mathematical questions arise out Mammen's theory. For instance, if we want Mammen's model to be able to account for all possible subsets of the universe (a property Mammen called "completeness"), then the Axiom of Choice, or at least some non-trivial consequences thereof, seem to play a role. There are also several interesting questions related to cardinal invariants, such as the "weight" of the underlying topological space of a complete Mammen space. I will give an overview of the mathematics of Mammen spaces and known results, and also discuss the numerous unsolved problems that remain. location: https://zoom.us/j/92701726800 http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

This Week in Logic at CUNY

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

- - - - Monday, Apr 18, 2022 - - - -



- - - - Tuesday, Apr 19, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 19, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Roman Kossak, CUNY
Absolute undefinability in arithmetic

I will survey some well-known and some more recent undefinability results about models of Peano Arithmetic. I want to contrast first-order undefinability in the standard model with a much stronger notion of undefinability which is suitable for resplendent models, and use the results to motivate some more general questions about the nature of undefinability.



- - - - Wednesday, Apr 20, 2022 - - - -



- - - - Thursday, Apr 21, 2022 - - - -



- - - - Friday, Apr 22, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 22, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass University of Michigan


Logic Workshop
CUNY Graduate Center, Friday, April 22, 2pm
In Person (contact Russell Miller by April 15 to be admitted into GC for the talk)
GC Room 5417
Jouko Väänänen University of Helsinki

Stationary logic and set theory

Stationary logic was introduced in the 1970’s. It allows the quantifier 'for almost all countable subsets s…'. Although it is undoubtedly a kind of second order logic, it is completely axiomatizable, countably compact and satisfies a kind of Downward Lowenheim-Skolem theorem. In this talk I give first a general introduction to the extension of first order logic by this 'almost all'-quantifier. As 'almost all' is interpreted as 'for a club of', the theory of this logic is entangled with properties of stationary sets. I will give some examples of this. The main reason to focus on this logic in my talk is to use it to build an inner model of set theory. I will give a general introduction to this inner model, called C(aa), or the aa-model, and sketch a proof of CH in the model. My work on the aa-model is joint work with Juliette Kennedy and Menachem Magidor.





Next Week in Logic at CUNY:

- - - - Monday, Apr 25, 2022 - - - -



- - - - Tuesday, Apr 26, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 26, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Michał Godziszewski, University of Vienna
Modal Quantifiers, Potential Infinity, and Yablo sequences

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




- - - - Wednesday, Apr 27, 2022 - - - -



- - - - Thursday, Apr 28, 2022 - - - -



- - - - Friday, Apr 29, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 29, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass University of Michigan




- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT:
Logic4Peace: fundraising online Logic event for Peace
University of Amsterdam
Dates: 22 and 23 April 2022
Venue: online (information will be provided to registered participants)

Logicians participating in this conference stand united for Peace. The on-going Russian military invasion in Ukraine is causing death, destruction and it is the direct cause of a gigantic humanitarian crisis. Educational facilities have been hit, supply chains have been broken and people have lost their families and homes. By organizing this conference, we offer our moral and financial support to our colleagues in Ukraine in this time of war.




- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

CMU seminars this week (logic, model theory, set theory)

Carnegie Mellon Logic Seminar
TUESDAY, April 19, 2022 Mathematical logic seminar: 3:30 P.M., Online, Samson Leung, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Categoricity results of abstract elementary classes (Part I) ABSTRACT: The notion of abstract elementary classes (AECs) is an axiomatic framework developed by Shelah to generalize classification theory beyond the first-order context. One central test question is the categoricity conjecture: if an AEC K is categorical in some $\mu\geq\beth_{(2^{LS(K)})^+}$, then it is categorical in all $\mu\geq\beth_{(2^{LS(K)})^+}$. After going through the axioms of AECs, we will overview some partial results in the literature, in particular those assuming tameness, type-shortness and the amalgamation property. We show that: assuming type-shortness and amalgamation over sets, the categoricity conjecture is true. Our result also provides an alternative proof to the upward categoricity transfer in first-order theories. TUESDAY, April 19, 2022 Set Theory Seminar: 4:30 P.M., Online, Samson Leung, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Categoricity results of abstract elementary classes (Part II) ABSTRACT: We will look at the main tools used in the proof of our categoricity transfer: good frames, multidimensional diagrams and primes. It is known that our assumptions allow a set-theoretic argument to transfer categoricity down to $\beth_{(2^{LS(K)})^+}$. We will discuss examples that encode the cumulative hierarchy, which have the first categoricity cardinals up to $\beth_{(2^{LS(K)})^+}$, but fail amalgamation. We conjecture that a more refined set-theoretic construction might provide such examples that also satisfy amalgamation, which will imply the above threshold is tight. THURSDAY, April 21, 2022 Model Theory Seminar: 11:00 A.M., Online, T. G. Kucera, University of Manitoba, Canada Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Saturated free algebras and almost indiscernible theories: an overview ABSTRACT: This is work motivated by questions at the intersection of algebra and model theory, and using advanced techniques of model theory. Baldwin and Shelah (Algebra Universalis, 1983) studied saturated free algebras. Pillay and Sklinos (Bull. Symb. Logic 2015), following the lead of this paper, studied "almost indiscernible theories", taking the opportunity to refine the statements of the major results and improve the proofs. We extend these results to large infinite contexts, both in the size of the language and the kinds of tuples allowed in an indiscernible set, and return to examples and applications in algebra, in particular in the theory of modules. The theory develops by noting various analogies. The idea of 'indiscernible sequence' generalizes various kinds of independence in algebra, including 'linearly independent set' in a vector space, 'free (generating) set' of an algebra, 'algebraic independence' in an algebraically closed field, and similar concepts. 'Saturated model' generalizes concepts such as 'injective envelope of a module', 'algebraic closure of a field', and similar constructions. A complete theory is "almost indiscernible" if it has a (sufficiently large) saturated model which lies in the algebraic closure of an indiscernible set (of sequences). Requiring that a saturated model be generated by an indiscernible set imposes strong structural constraints, but nonetheless there are natural motivating examples. This will be a talk without proofs. If there is sufficient interest I can return at a later time to cover the proofs of the main model-theoretic results. I start with some history and motivation from algebra, and then introduce our extension of the definition of an "almost indiscernible theory". I will give a summary of the main results, in particular that such a theory T is superstable, stable in |T|, and non-multi-dimensional. I'll only mention briefly the main tools of the proofs. Then I will present some consequences for free algebras and for theories of modules, including structure theorems and some examples. I conclude with a list of open questions. This is joint work with Anand Pillay Article link: https://link.springer.com/article/10.1007/s00012-021-00766-x

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 20th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Claudio Agostini -- On some extensions of theorems in combinatorics Ramsey monoids have been introduced by Solecki in 2019 to generalize and extend famous theorems in combinatorics such as Hindman’s theorem, Carlson’s Theorem on variable words, and Gowers’ $\mathrm{FIN}_k$ Theorem. In short, a monoid is Ramsey if for every action of the monoid on a semigroup and for any finite coloring of the semigroup there is an infinite monochromatic ``nice set'' closed to a certain degree under the operation of the semigroup and the action of the monoid. Relaxing or strengthening the requirements that the ``nice set'' must satisfies, one can obtain other classes of monoids, like $\mathbb{Y}$-controllable monoids, locally Ramsey monoids and locally $\mathbb{Y}$-controllable monoids. In this talk, I will introduce these notions and discuss some recent progress in the study of these classes. This is a joint work with Eugenio Colla. Best, David

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 13th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Chodounsky -- Colors of the pseudotree The pseudotree is the Fraisse limit of the class of finite trees with embeddings which respect the meet operation. In this short talk I will cover the little we know about the big Ramsey degrees of substructures of the pseudotree. This is joint work Monroe Eskew and Thilo Weinert. Best, David

This Week in Logic at CUNY

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

- - - - Monday, Apr 11, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 11, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Justin Bledin (Johns Hopkins)
Title: From Truthmaker to Menu Semantics

Abstract: The logical foundations of English and other natural languages are often assumed to have an essentially truth-theoretic character where the meanings of connectives and quantifiers are grounded in the truth and falsity of sentences. In this talk, I explore a fundamentally different perspective that shifts the focus from the truth value to the ‘menu’. Under this alternative conception of the logic of natural language, speakers manifest their logical competence by, metaphorically speaking, constructing and combining menus of items in various types throughout the grammar. The logical connectives are ‘menu constructors’: negation can be used to express that items are ‘off’ the menu, conjunction produces combinations of ‘on-menu’ items, and disjunction introduces choice between items. My point of departure for this truth displacing project is, oddly enough, recent work in ‘truthmaker’ or ‘exact’ semantics. What I try to do is build a bridge between the standard theory of truthmaker semantics (van Fraassen 1969; Fine 2017), which assigns menus of truthmakers and falsemakers at the sentential level, and compositional semantics in the general style of Montague. One of the most striking aspects of the theory is its treatment of noun phrases, as both quantificational and non-quantificational NPs are all assigned both denotations and ‘anti-denotations’ drawn or constructed from a rich entity space populated by both positive and negative individuals and their sums. Towards the end of the talk, I will try to bring out the explanatory power of menu semantics by applying it to a couple of problem areas in natural language quantification.




- - - - Tuesday, Apr 12, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 12, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Thomas Ferguson University of Amsterdam and University of St. Andrews




- - - - Wednesday, Apr 13, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Alex Martsinkovsky, Northeastern University.
Date and Time:     Wednesday April 13, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     A Reflector in Search of a Category.

Abstract: The last several months have seen an explosive growth of activities centered around the defect of a finitely presented functor. This notion made its first appearance in M. Auslander's fundamental work on coherent functors in the mid-1960s, although at that time it was mostly used just as a technical tool. A phenomenological study of that concept was initiated by Jeremy Russell in 2016. What transpired in the recent months is the ubiquitous nature of the defect, explained in part by the fact that it is adjoint to the Yoneda embedding. Thus any branch of mathematics, computer science, physics, or any applied science that references the Yoneda embedding automatically becomes a candidate for applications of the defect.

In this expository talk I will first give a streamlined introduction to the original notion of defect of a finitely presented functor defined on a module category and then show how to generalize it to arbitrary additive functors. Along the way I will give a dozen or so examples illustrating various use cases for the defect. The ultimate goal of this lecture is to provide a background for the upcoming talk of Alex Sorokin, who will report on his vast generalization of the defect to arbitrary profunctors enriched in a cosmos.

This presentation is based on joint work in progress with Jeremy Russell.




- - - - Thursday, Apr 14, 2022 - - - -



- - - - Friday, Apr 15, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 15, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Joel David Hamkins, Notre Dame University

The surprising strength of reflection in second-order set theory with abundant urelements

I shall give a general introduction to urelement set theory and the role of the second-order reflection principle in second-order urelement set theory GBCU and KMU. With the abundant atom axiom, asserting that the class of urelements greatly exceeds the class of pure sets, the second-order reflection principle implies the existence of a supercompact cardinal in an interpreted model of ZFC. The proof uses a reflection characterization of supercompactness: a cardinal  is supercompact if and only if for every second-order sentence true in some structure  (of any size) is also true in a first-order elementary substructure  of size less than . This is joint work with Bokai Yao. http://jdh.hamkins.org/surprising-strength-of-reflection-with-abundant-urelements-cuny-set-theory-seminar-april-2022



Next Week in Logic at CUNY:

- - - - Monday, Apr 18, 2022 - - - -



- - - - Tuesday, Apr 19, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 19, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Roman Kossak, CUNY
Absolute undefinability in arithmetic

I will survey some well-known and some more recent undefinability results about models of Peano Arithmetic. I want to contrast first-order undefinability in the standard model with a much stronger notion of undefinability which is suitable for resplendent models, and use the results to motivate some more general questions about the nature of undefinability.



- - - - Wednesday, Apr 20, 2022 - - - -



- - - - Thursday, Apr 21, 2022 - - - -



- - - - Friday, Apr 22, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 22, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass University of Michigan


Logic Workshop
CUNY Graduate Center, Friday, April 22, 2pm
In-person only: CUNY Graduate Center Room 6496
Jouko Väänänen University of Helsinki



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT:
Logic4Peace: fundraising online Logic event for Peace
University of Amsterdam
Dates: 22 and 23 April 2022
Venue: online (information will be provided to registered participants)

Logicians participating in this conference stand united for Peace. The on-going Russian military invasion in Ukraine is causing death, destruction and it is the direct cause of a gigantic humanitarian crisis. Educational facilities have been hit, supply chains have been broken and people have lost their families and homes. By organizing this conference, we offer our moral and financial support to our colleagues in Ukraine in this time of war.




- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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Upcoming seminars (logic, model theory, set theory)

Carnegie Mellon Logic Seminar
TUESDAY, April 12, 2022 Mathematical logic seminar: 3:30 P.M., Online, Garrett Ervin, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Filter flows ABSTRACT: A directed hypergraph G consists of a vertex set V along with a collection of directed hyperedges (A, B), where A and B are finite subsets of V. Given a set of vertices X, we think of the edge (A, B) as being on the boundary of X if X intersects A and does not completely contain B. We can generalize the notion of directed hypergraph as follows. A _filter graph_ G consists of an infinite vertex set V along with a collection of edges (F, G), where F and G are filters on V. Given a set of vertices X, we think of the edge (F, G) as being on the boundary of X if X is F-positive and the complement of X is G-positive. Filter graphs seem to be surprisingly graph-like. We'll show in this talk that filter graphs satisfy the natural generalization of the max-flow/min-cut theorem, where point masses flowing along directed edges in the usual hypergraph setting are replaced by ultrafilters flowing along filter-edges. TUESDAY, April 19, 2022 Mathematical logic seminar: 3:30 P.M., Online, Samson Leung, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Categoricity results of abstract elementary classes (Part I) ABSTRACT: The notion of abstract elementary classes (AECs) is an axiomatic framework developed by Shelah to generalize classification theory beyond the first-order context. One central test question is the categoricity conjecture: if an AEC K is categorical in some $\mu\geq\beth_{(2^{LS(K)})^+}$, then it is categorical in all $\mu\geq\beth_{(2^{LS(K)})^+}$. After going through the axioms of AECs, we will overview some partial results in the literature, in particular those assuming tameness, type-shortness and the amalgamation property. We show that: assuming type-shortness and amalgamation over sets, the categoricity conjecture is true. Our result also provides an alternative proof to the upward categoricity transfer in first-order theories. TUESDAY, April 19, 2022 Set Theory Reading Group: 4:30 P.M., Online, Samson Leung, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Categoricity results of abstract elementary classes (Part II) ABSTRACT: We will look at the main tools used in the proof of our categoricity transfer: good frames, multidimensional diagrams and primes. It is known that our assumptions allow a set-theoretic argument to transfer categoricity down to $\beth_{(2^{LS(K)})^+}$. We will discuss examples that encode the cumulative hierarchy, which have the first categoricity cardinals up to $\beth_{(2^{LS(K)})^+}$, but fail amalgamation. We conjecture that a more refined set-theoretic construction might provide such examples that also satisfy amalgamation, which will imply the above threshold is tight. THURSDAY, April 21, 2022 Model Theory Seminar: 11:00 A.M., Online, T. G. Kucera, University of Manitoba, Canada Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Saturated free algebras and almost indiscernible theories: an overview ABSTRACT: This is work motivated by questions at the intersection of algebra and model theory, and using advanced techniques of model theory. Baldwin and Shelah (Algebra Universalis, 1983) studied saturated free algebras. Pillay and Sklinos (Bull. Symb. Logic 2015), following the lead of this paper, studied "almost indiscernible theories", taking the opportunity to refine the statements of the major results and improve the proofs. We extend these results to large infinite contexts, both in the size of the language and the kinds of tuples allowed in an indiscernible set, and return to examples and applications in algebra, in particular in the theory of modules. The theory develops by noting various analogies. The idea of 'indiscernible sequence' generalizes various kinds of independence in algebra, including 'linearly independent set' in a vector space, 'free (generating) set' of an algebra, 'algebraic independence' in an algebraically closed field, and similar concepts. 'Saturated model' generalizes concepts such as 'injective envelope of a module', 'algebraic closure of a field', and similar constructions. A complete theory is "almost indiscernible" if it has a (sufficiently large) saturated model which lies in the algebraic closure of an indiscernible set (of sequences). Requiring that a saturated model be generated by an indiscernible set imposes strong structural constraints, but nonetheless there are natural motivating examples. This will be a talk without proofs. If there is sufficient interest I can return at a later time to cover the proofs of the main model-theoretic results. I start with some history and motivation from algebra, and then introduce our extension of the definition of an "almost indiscernible theory". I will give a summary of the main results, in particular that such a theory T is superstable, stable in |T|, and non-multi-dimensional. I'll only mention briefly the main tools of the proofs. Then I will present some consequences for free algebras and for theories of modules, including structure theorems and some examples. I conclude with a list of open questions. This is joint work with Anand Pillay Article link: https://link.springer.com/article/10.1007/s00012-021-00766-x THURSDAY, April 28, 2022 Model Theory Seminar: 11:00 A.M., Online, Jonathan Kirby, The University of East Anglia Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Independence Relations for Exponential Fields ABSTRACT: In classical first-order logic, the presence of an independence relation on models of a complete theory T can be used to show that T is strongly minimal, stable, simple, or NSOP_1. Something analogous works in various generalisations of first-order logic, including AECs. In this talk I will illustrate the general principle by constructing various independence relations on exponential fields, that is, fields equipped with a homomorphism from their additive group to their multiplicative group, like the usual real and complex exponential maps. These independence relations can be used to prove that various AECs of exponential fields are quasiminimal, stable, or NSOP_1. In some of the stable cases, there are open questions around extending from the countable models, which are well-understood, to the uncountable ones. This is joint work with Levon Haykazyan, Robert Henderson, Mark Kamsma, and Vahagn Aslanyan.

Logic Seminar 13 April 2022 16:00 hrs at NUS by Wang Wei, Sun Yatsen University

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 13 April 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Wang Wei Title: Ackermann, Ramsey and Trees URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Recently, Chong, Yang and I prove that a version of Pigeonholes Principle for trees (TT^1) is Pi^0_3-conservative over RCA_0. So, TT^1 does not imply the totality of Ackermann function over RCA_0, like the instance of Ramsey's Theorem for 2-colorings of pairs. To fit the trend of logic talks, I am not going to present many details. Instead, I will try to recall some stories about the Ackermann function and its appearance in reverse mathematics.

Logic Seminar 6 April 2022 16:00 hrs by Frank Stephan, NUS

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 6 April 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Frank Stephan Title: Matching Regular Pumping Lemmas and Automaticity Abstract: The talk investigates which versions of the pumping lemma are matching where matching means that exactly the regular languages satisfy it. In particular it will be shown that two-sided pumping lemmas where an automatic function computes the pump tend to be matching. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Cross-Alps Logic Seminar (speaker: Alexander S. Kechris)

Cross-Alps Logic Seminar
On Friday 08.04.2022 at 16:00 CEST
Alexander S. Kechris (Caltech)
will give a talk on
Countable sections for actions of locally compact groups

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to 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 2017 'Mathematical logic: models, sets, computability'.


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This Week in Logic at CUNY

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

- - - - Monday, Apr 4, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 4, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Jenn McDonald (Columbia)
Title: Causal Relativism

Abstract: In this talk, I defend a kind of causal relativism. I argue that actual causation cannot be taken to hold simpliciter between two particular things (‘things’ such as events, states-of-affairs, etc.).  Instead, actual causation holds only relative to a background space of possibilities – a modal profile.  The argument applies generally to any difference-making analysis of actual causation.  But I will use the framework of structural equation models to make the case.   I first demonstrate that structural equation models represent situations in this way – as relative to some modal profile or other.  This observation is underappreciated in the literature.  I show how it raises a problem for all extant analyses of actual causation in terms of these models.  This problem is best responded to by a kind of causal relativism, or so I will argue.  Notably, the problem cannot be avoided by rejecting a structural equation framework.  While the framework is useful for its illustration, the problem arises for any analysis governed by the idea that a cause is what makes a difference in an effect’s occurrence.




- - - - Tuesday, Apr 5, 2022 - - - -



- - - - Wednesday, Apr 6, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Jason Parker, Brandon University in Manitoba.

Date and Time:     Wednesday April 6, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities.


Abstract: Several structure-semantics adjunctions and monad-theory equivalences have been established in category theory. Lawvere (1963) developed a structure-semantics adjunction between Lawvere theories and tractable Set-valued functors, which was subsequently generalized by Linton (1969), while Dubuc (1970) established a structure-semantics adjunction between V-theories and tractable V-valued V-functors for a symmetric monoidal closed category V. It is also well known (and due to Linton) that there is an equivalence between Lawvere theories and finitary monads on Set. Generalizing this result, Lucyshyn-Wright (2016) established a monad-theory equivalence for eleutheric systems of arities in arbitrary closed categories. Building on earlier work by Nishizawa and Power, Bourke and Garner (2019) subsequently proved a general monad-theory equivalence for arbitrary small subcategories of arities in locally presentable enriched categories. However, neither of these equivalences generalizes the other, and there has not yet been a general treatment of enriched structure-semantics adjunctions that specializes to those established by Lawvere, Linton, and Dubuc.

Motivated by these considerations, we develop a general axiomatic framework for studying enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities, which generalizes all of the aforementioned results and also provides substantial new examples of relevance for topology and differential geometry. For a subcategory of arities J in a V-category C over a symmetric monoidal closed category V, Linton’s notion of clone generalizes to provide enriched notions of J-theory and J-pretheory, which were also employed by Bourke and Garner (2019). We say that J is amenable if every J-theory admits free algebras, and is strongly amenable if every J-pretheory admits free algebras. If J is amenable, then we obtain an idempotent structure-semantics adjunction between certain J-pretheories and J-tractable V-categories over C, which yields an equivalence between J-theories and J-nervous V-monads on C. If J is strongly amenable, then we also obtain a rich theory of presentations for J-theories and J-nervous V-monads. We show that many previously studied subcategories of arities are (strongly) amenable, from which we recover the aforementioned structure-semantics adjunctions and monad-theory equivalences. We conclude with the result that any small subcategory of arities in a locally bounded closed category is strongly amenable, from which we obtain structure-semantics adjunctions and monad-theory equivalences in (e.g.) many convenient categories of spaces.

Joint work with Rory Lucyshyn-Wright.




- - - - Thursday, Apr 7, 2022 - - - -



- - - - Friday, Apr 8, 2022 - - - -



Next Week in Logic at CUNY:

- - - - Monday, Apr 11, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 11, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Justin Bledin (Johns Hopkins)
Title: From Truthmaker to Menu Semantics

Abstract: The logical foundations of English and other natural languages are often assumed to have an essentially truth-theoretic character where the meanings of connectives and quantifiers are grounded in the truth and falsity of sentences. In this talk, I explore a fundamentally different perspective that shifts the focus from the truth value to the ‘menu’. Under this alternative conception of the logic of natural language, speakers manifest their logical competence by, metaphorically speaking, constructing and combining menus of items in various types throughout the grammar. The logical connectives are ‘menu constructors’: negation can be used to express that items are ‘off’ the menu, conjunction produces combinations of ‘on-menu’ items, and disjunction introduces choice between items. My point of departure for this truth displacing project is, oddly enough, recent work in ‘truthmaker’ or ‘exact’ semantics. What I try to do is build a bridge between the standard theory of truthmaker semantics (van Fraassen 1969; Fine 2017), which assigns menus of truthmakers and falsemakers at the sentential level, and compositional semantics in the general style of Montague. One of the most striking aspects of the theory is its treatment of noun phrases, as both quantificational and non-quantificational NPs are all assigned both denotations and ‘anti-denotations’ drawn or constructed from a rich entity space populated by both positive and negative individuals and their sums. Towards the end of the talk, I will try to bring out the explanatory power of menu semantics by applying it to a couple of problem areas in natural language quantification.




- - - - Tuesday, Apr 12, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 12, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Thomas Ferguson University of Amsterdam and University of St. Andrews




- - - - Wednesday, Apr 13, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Alex Martsinkovsky, Northeastern University.
Date and Time:     Wednesday April 13, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     A Reflector in Search of a Category.

Abstract: The last several months have seen an explosive growth of activities centered around the defect of a finitely presented functor. This notion made its first appearance in M. Auslander's fundamental work on coherent functors in the mid-1960s, although at that time it was mostly used just as a technical tool. A phenomenological study of that concept was initiated by Jeremy Russell in 2016. What transpired in the recent months is the ubiquitous nature of the defect, explained in part by the fact that it is adjoint to the Yoneda embedding. Thus any branch of mathematics, computer science, physics, or any applied science that references the Yoneda embedding automatically becomes a candidate for applications of the defect.

In this expository talk I will first give a streamlined introduction to the original notion of defect of a finitely presented functor defined on a module category and then show how to generalize it to arbitrary additive functors. Along the way I will give a dozen or so examples illustrating various use cases for the defect. The ultimate goal of this lecture is to provide a background for the upcoming talk of Alex Sorokin, who will report on his vast generalization of the defect to arbitrary profunctors enriched in a cosmos.

This presentation is based on joint work in progress with Jeremy Russell.




- - - - Thursday, Apr 14, 2022 - - - -



- - - - Friday, Apr 15, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 1, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Joel David Hamkins Notre Dame University



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT:
Logic4Peace: fundraising online Logic event for Peace
University of Amsterdam
Dates: 22 and 23 April 2022
Venue: online (information will be provided to registered participants)

Logicians participating in this conference stand united for Peace. The on-going Russian military invasion in Ukraine is causing death, destruction and it is the direct cause of a gigantic humanitarian crisis. Educational facilities have been hit, supply chains have been broken and people have lost their families and homes. By organizing this conference, we offer our moral and financial support to our colleagues in Ukraine in this time of war.




- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

Damian Sobota, Measures with the Additive Property and the random forcing

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 5.04.2022, at 13.15, room 403 Speaker: Damian Sobota, (KGRC Vienna) Title: Measures with the Additive Property and the random forcing Abstact: "Let μ be a finitely additive probability measure on ω which vanishes on points, that is, μ({n})=0 for every n∈ω. It follows immediately that μ is not σ-additive, however it may be almost σ-additive in the following weak sense. We say that μ has the Additive Property, (AP) in short, if for every sequence (A_n) of pairwise disjoint subsets of ω there is a subset A such that A_n\A is finite for every n∈ω and μ(A)=Σ_n μ(A_n). Equivalently, for every decreasing sequence (A_n) of subsets of ω there is a subset A such that A\A_n is finite for every n∈ω and μ(A)=lim_n μ(A_n). The latter definition implies immediately that, e.g., an ultrafilter U on ω is a P-point if and only if the one-point measure δ_U has (AP). And similarly as in the case of P-points the existence of measures with (AP) is independent of ZFC. During my talk I will discuss basic properties of (families of) measures with (AP) as well as show, at least briefly, that using old ideas of Solovay and Kunen one can obtain a non-atomic measure with (AP) in the random model. The latter result implies that in this model there exists a ccc P-set in ω*, which may be treated as a (weak) partial answer to the question asking whether there are P-points in the random model. This is a joint work with Piotr Borodulin-Nadzieja." Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Next math logic seminar on Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, April 5, 2022 Mathematical logic seminar: 3:30 P.M., Online, Benjamin Siskind, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: An update on order-preserving Martin's Conjecture ABSTRACT: Martin's Conjecture is a way of codifying a phenomenon observed in computability theory: the only natural functions on the Turing degrees seem to be the constant functions, the identity, and the transfinite iterates of the Turing jump. While the full conjecture is wide open, there has been significant progress on order-preserving Martin's Conjecture--that is, Martin's Conjecture restricted to the functions which preserve Turing-reducibility. In particular, the order-preserving version has been settled positively for Borel functions whereas Martin's Conjecture for even low-level Borel functions is open. In this talk, we'll discuss a plan for pushing order-preserving Martin's Conjecture beyond Borel functions involving some AD combinatorics, higher recursion theory, and forcing. This is joint, in-progress work with Patrick Lutz.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 6th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jinřich Zapletal -- Pairs of generic extensions I will present several natural variations of the notion of mutual genericity for forcing extensions, show how to produce interesting examples, and use them for consistency results in choiceless set theory. Best, David

(KGRC) Set Theory Research Seminar talk on Tuesday, April 5

Kurt Godel Research Center
Set Theory Research Seminar Kurt Gödel Research Center Tuesday, April 5 "Fresh function spectra" Wolfgang Wohofsky (KGRC) My talk will be about the notion of fresh function and I will discuss the corresponding spectrum. A function with domain lambda is fresh if it is new but all its initial segments are in the ground model. I will give general facts how to compute the fresh function spectrum, also discussing what sets are realizable as a fresh function spectrum of a forcing. Moreover, I will provide several examples, including well-known tree forcings on omega such as Sacks, Laver, Miller, and Mathias forcing, as well as Prikry and Namba forcing to illustrate the difference between fresh functions and fresh subsets. This is joint work with Vera Fischer and Marlene Koelbing. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This Friday April 1, 13:30 (EDT, GMT -4) Philipp Schlicht will give a talk at the Toronto Set Theory Seminar @ The Fields Institute Title: Dichotomies for open directed hypergraphs on generalised Baire spaces Abstract: The open graph dichotomy for a subset X of the Baire space states that any open graph on X either contains a large complete subgraph or admits a countable colouring. It is a definable version of the open colouring axiom for X and generalises the perfect set property. Recently, this was generalised to infinite dimensions by Miller, Carroy and Soukup. I will discuss extensions of this result to generalised Baire spaces and a number of applications such as variants of the Hurewicz dichotomy, the determinacy of Väänänen's game and the asymmetric Baire property. This is a joint project with Dorottya Sziraki. Location: https://zoom.us/j/92701726800

Cross-Alps Logic Seminar (speaker: David Evans)

Cross-Alps Logic Seminar
On Friday 01.04.2022 at 16:00
David Evans (Imperial College London)
will give a talk on
Amalgamation properties in measured structures

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to 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 2017 'Mathematical logic: models, sets, computability'.



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This Week in Logic at CUNY

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

- - - - Monday, Mar 28, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 28, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Dongwoo Kim (CUNY).
Title: Necessity, Essence and Explanation

Abstract: I shall discuss some of the relations between metaphysical modality, essence and explanation. The essentialist approach to metaphysical modality seeks to give an account of necessity (and thus of possibility) as having its source in essence. But what is essence, and in what sense and how does it give rise to necessity? In their recent paper “Essential Properties are Super-Explanatory: Taming Metaphysical Modality” (2020), Marion Godman, Antonella Mallozzi and David Papineau have attempted to address these issues with respect to aposteriori necessities concerning kinds. According to their account, the essence of a kind consists in the super-explanatory property—a single property that is causally responsible for a multitude of commonalities shared by the instances of the kind. And they argue that this super-explanatory notion of essence offers a principled account of aposteriori necessities concerning kinds. In this talk, I am going to argue that their account is not satisfactory. I shall examine two main arguments of GMP that the super-explanatory property of a kind is metaphysically necessary and argue that they both are fallacious. Along the way, a general problem will emerge that applies to any account that tries to explicate the notion of essence in terms of an explanatory relation.





- - - - Tuesday, Mar 29, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 29, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Erez Shochat, St. Francis College
A Survey on the Automorphism Groups of Countable (Boundedly) Recursively Saturated Models of PA

In this talk we discuss important results concerning the automorphism groups of countable recursively saturated models of PA and automorphism groups of the countable boundedly recursively saturated models of PA which are short (aka short recursively saturated models). We compare and contrast and also list some open questions.




- - - - Wednesday, Mar 30, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Morgan Rogers, Universit`a degli Studi dell’Insubria.

Date and Time:     Wednesday March 30, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Toposes of Topological Monoid Actions.


Abstract: Anyone encountering topos theory for the first time will be familiar with the fact that the category of actions of a monoid on sets is a special case of a presheaf topos. It turns out that if we equip the monoid with a topology and consider the subcategory of continuous actions, the result is still a Grothendieck topos. It is possible to characterize such toposes in terms of their points, and along the way extract canonical representing topological monoids, the complete monoids. I'll sketch the trajectory of this story, present some positive and negative results about Morita-equivalence of topological monoids, and explain how one can extract a semi-Galois theory from this set-up.



- - - - Thursday, Mar 31, 2022 - - - -



- - - - Friday, Apr 1, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 1, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Vera Fischer, University of Vienna



Next Week in Logic at CUNY:

- - - - Monday, Apr 4, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 4, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Jenn McDonald (Columbia)
Title: Causal Relativism

Abstract: In this talk, I defend a kind of causal relativism. I argue that actual causation cannot be taken to hold simpliciter between two particular things (‘things’ such as events, states-of-affairs, etc.).  Instead, actual causation holds only relative to a background space of possibilities – a modal profile.  The argument applies generally to any difference-making analysis of actual causation.  But I will use the framework of structural equation models to make the case.   I first demonstrate that structural equation models represent situations in this way – as relative to some modal profile or other.  This observation is underappreciated in the literature.  I show how it raises a problem for all extant analyses of actual causation in terms of these models.  This problem is best responded to by a kind of causal relativism, or so I will argue.  Notably, the problem cannot be avoided by rejecting a structural equation framework.  While the framework is useful for its illustration, the problem arises for any analysis governed by the idea that a cause is what makes a difference in an effect’s occurrence.




- - - - Tuesday, Apr 5, 2022 - - - -



- - - - Wednesday, Apr 6, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Jason Parker, Brandon University in Manitoba.

Date and Time:     Wednesday April 6, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities.


Abstract: Several structure-semantics adjunctions and monad-theory equivalences have been established in category theory. Lawvere (1963) developed a structure-semantics adjunction between Lawvere theories and tractable Set-valued functors, which was subsequently generalized by Linton (1969), while Dubuc (1970) established a structure-semantics adjunction between V-theories and tractable V-valued V-functors for a symmetric monoidal closed category V. It is also well known (and due to Linton) that there is an equivalence between Lawvere theories and finitary monads on Set. Generalizing this result, Lucyshyn-Wright (2016) established a monad-theory equivalence for eleutheric systems of arities in arbitrary closed categories. Building on earlier work by Nishizawa and Power, Bourke and Garner (2019) subsequently proved a general monad-theory equivalence for arbitrary small subcategories of arities in locally presentable enriched categories. However, neither of these equivalences generalizes the other, and there has not yet been a general treatment of enriched structure-semantics adjunctions that specializes to those established by Lawvere, Linton, and Dubuc.

Motivated by these considerations, we develop a general axiomatic framework for studying enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities, which generalizes all of the aforementioned results and also provides substantial new examples of relevance for topology and differential geometry. For a subcategory of arities J in a V-category C over a symmetric monoidal closed category V, Linton’s notion of clone generalizes to provide enriched notions of J-theory and J-pretheory, which were also employed by Bourke and Garner (2019). We say that J is amenable if every J-theory admits free algebras, and is strongly amenable if every J-pretheory admits free algebras. If J is amenable, then we obtain an idempotent structure-semantics adjunction between certain J-pretheories and J-tractable V-categories over C, which yields an equivalence between J-theories and J-nervous V-monads on C. If J is strongly amenable, then we also obtain a rich theory of presentations for J-theories and J-nervous V-monads. We show that many previously studied subcategories of arities are (strongly) amenable, from which we recover the aforementioned structure-semantics adjunctions and monad-theory equivalences. We conclude with the result that any small subcategory of arities in a locally bounded closed category is strongly amenable, from which we obtain structure-semantics adjunctions and monad-theory equivalences in (e.g.) many convenient categories of spaces.

Joint work with Rory Lucyshyn-Wright.




- - - - Thursday, Apr 7, 2022 - - - -



- - - - Friday, Apr 8, 2022 - - - -







- - - - 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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Kacper Kucharski, Using elementary submodels in topology

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 29.03.2022, at 13.15, room 403 Speaker: Kacper Kucharski, (MIM UW) Title: Using elementary submodels in topology Abstact: "The main goal of the talk is to present proofs of interesting topological theorems using elementary submodels. One theorem will be the classical Arhangel'skii's result which says that the cardinality of a compact Hausdorff first countable space is at most the continuum. The second part of the talk will be focused on presenting so-called reflection results e.g., Dow's theorem: every nonmetrizable compact Hausdorff space contains a nonmetrizable subspace of cardinality ω_1" Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 30th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Ziemowit Kostana -- Games played with diamonds Parametrized diamonds are combinatorial principles that imply many consequences of the original Jensen's Diamond, yet are consistent with the CH failing. Informally speaking, they are in similar relation to Jensen's Diamond, as cardinal invariants of the Cichoń's diagram are to CH. The modern framework for these axioms was described by Dzamonja, Hrusak, and ... I would like to show that some equivalent, or "almost-equivalent", axioms can be formulated in a completely different, game-theoretic, language. This gives additional insight on how these axioms affect the universe of sets. Best, David

Logic Seminar Wednesday 30 March 2022 16:00 hrs at NUS by Wu Liuzhen

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 30 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Wu Liuzhen Title: Continuum function and strongly compact cardinal URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The continuum function is a key and long-studied object inside set theory. We will survey the study on the behavior of continuum function in presence of strongly compact cardinals. We will also introduce some major research problems in this area. Finally, We discuss our recent work on forcing continuum function of some special pattern.

(KGRC) seminar talks Tuesday, March 29 and Thursday, March 31

Kurt Godel Research Center
For the two most recent sessions in the Set Theory Research Seminar, video has been recorded. So if you missed them or want to rewatch them, here they are: Jeffrey Bergfalk, "A family of higher dimensional partition principles" https://univienna.zoom.us/rec/share/iYgs9rLaHvrhRtdXzF4Swr31cGn0kZZchw0Qp_GBFWkV2h2P1k-NThPDZ2y43-GO.SQrJ2KqoAMvNPG91 Passcode vN70.uy1 Stefan Hoffelner, "Forcing the \Pi^1_n-uniformization property" https://univienna.zoom.us/rec/share/4AI5rQ3rTJTGyOFwTZXvdCb2T3pPC4nBwBLuXZSFvctbA_b4U4wuuTt8sPKdYFwv.PehtSISZx_8QLZnE Passcode Vkf%0@TD * * * Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 29 "P-measures in the random forcing" Damian Sobota (KGRC) Let $\mu$ be a finitely additive probability measure on $\omega$ which vanishes on points, that is, $\mu(\{n\})=0$ for every $n$. It follows immediately that $\mu$ is not $\sigma$-additive, however it may be almost $\sigma$-additive in the following weak sense. We say that $\mu$ is a \textit{P-measure} if for every decreasing sequence $(A_n)$ of subsets of $\omega$ there is a subset $A$ such that $A\setminus A_n$ is finite for every $n$ and $\mu(A)=\lim_n \mu(A_n)$. It follows immediately that, e.g., an ultrafilter $\mathcal{U}$ on $\omega$ is a P-point if and only if the one-point measure $\delta_\mathcal{U}$ is a P-measure. And similarly as in the case of P-points the existence of P-measures is independent of ZFC. During my talk I will discuss basic properties of P-measures and show, at least briefly, that using old ideas of Solovay and Kunen one can obtain a non-atomic P-measure in the random model. The latter result implies that in this model there exists a nowhere dense ccc P-set in $\omega^*$, which may be treated as a (weak) partial answer to the question asking whether there are P-points in the random model. This is a joint work with Piotr Borodulin-Nadzieja. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universit?t Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt G?del Research Center Thursday, March 31 "Small uncountable objects in Banach space theory" Damian Sobota (KGRC) During my talk I will provide several examples presenting the impact which the (non-)existence of miscellaneous uncountable combinatorial and set-theoretic substructures of various basic spaces (such as the set $P(\mathbb{N})$ of all subsets of the set $\mathbb{N}$ of natural numbers or the set $\mathbb{N}^\mathbb{N}$ of all functions from $\mathbb{N}$ into $\mathbb{N}$) has on structural and topological properties of Banach spaces. Time and Place Talk at 3:00pm Universit?t Wien Institut f?r Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

Two seminars March 29: Ibarlucía (10AM) and Neeman (3:30PM)

Carnegie Mellon Logic Seminar
TUESDAY, March 29, 2022 Set Theory Seminar: 10:30 A.M., Online, Tomás Ibarlucía, Université de Paris Please note the unusual time. Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Approximate isomorphism of randomizations with a distinguished small substructure ABSTRACT: I will discuss a joint work with James Hanson in which we study the relation of approximate isomorphism in a certain class of metric structures---specifically, randomizations (in the sense of Ben Yaacov--Keisler) of omega-categorical, omega-stable classical structures, enriched with a predicate for a distinguished small elementary substructure; "small" meaning that the pair consisting of the randomization and its substructure forms a model of the theory of beautiful pairs (in the sense of Poizat) of models of the randomized theory. An approximate isomorphism between two such pairs is an isomorphism of the randomizations that brings the distinguished elementary substructures close in the Hausdorff metric. We prove that for randomized infinite sets with no further structure, any two pairs of this kind are approximately isomorphic (and that this extends to other cases). On the other hand, we show that approximate isomorphism fails for certain pairs of randomized vector spaces over finite sets (and, in fact, for a much larger class of examples). These results provide both a new positive instance and a refutation of a conjecture of Ben Yaacov--Berenstein--Henson, which claimed that if T is an omega-categorical, omega-stable metric theory, then the theory of beautiful pairs of models of T should be approximately omega-categorical. TUESDAY, March 29, 2022 Mathematical logic seminar: 3:30 P.M., Online, Itay Neeman, UCLA Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Restrictions of OCA_T with large continuum ABSTRACT: Todorcevic's Open Coloring Axiom (OCA_T) states that any open graph on a separable metric space is either countably chromatic, or admits an uncountable clique. OCA_T has many interesting and important applications. Its known consistency proofs all lead to models where the continuum is $\aleph_2$. It is therefore natural to ask whether it implies that the continuum is $\aleph_2$, or whether there are other consistency proofs leading to models with larger continuum. (OCA_T negates the CH.) This question is still open. However we show that the restriction of OCA_T to spaces of size less than the continuum is consistent with arbitrarily large values of the continuum. Earlier work by Farah obtained this for the restriction to spaces of size $\aleph_1$

Correction to previous subject line

Carnegie Mellon Logic Seminar
Two seminars March 29: Ibarlucía (10:30AM) and Neeman (3:30PM)

Cross-Alps Logic Seminar (speaker: Omer Ben-Neria)

Cross-Alps Logic Seminar
On Friday 25.03.2022 at 16:00

Omer Ben-Neria (The Hebrew University of Jerusalem)

will give a talk on

Mathias-type Criterion for the Magidor Iteration of Prikry forcings

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 2017 'Mathematical logic: models, sets, computability'.



Mail priva di virus. www.avast.com

Logic Seminar at NUS on Wed 23 March 2022 at 16:00 hrs by Wu Guohua, NTU

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 23 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Wu Guohua Title: Splittings and nonsplittings of computably enumerable sets Abstract: In this talk, I will review some existing work on splittings of c.e. sets, and then present an ongoing paper on nonsplitting, a joint work with Downey. The main result is the following. Theorem: There are c.e. sets A and B such that B is strictly Turing reducible to A and for any c.e. sets U, V, if U and V form a set-splitting of A, then one of them is Turing reducible to B. 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, Mar 21, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 21, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Noson Yanofsky (CUNY)
Title: Why Mathematics Works so Well

Abstract: A major question in philosophy of science involves the unreasonable effectiveness of mathematics in physics. Why should mathematics, created or discovered, with nothing empirical in mind be so perfectly suited to describe the laws of the physical universe? To answer this, we review the well-known fact that the defining properties of the laws of physics are their symmetries. We then show that there are similar symmetries of mathematical facts and that these symmetries are the defining properties of mathematics. By examining the symmetries of physics and mathematics, we show that the effectiveness is actually quite reasonable. In essence, we show that the regularities of physics are a subset of the regularities of mathematics.



- - - - Tuesday, Mar 22, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 22, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Ermek Nurkhaidarov, Penn State Mont Alto
Generic Automorphisms

In this talk we investigate generic automorphisms of countable models. Hodges-Hodkinson-Lascar- Shelah 93 introduces the notion of SI (small index) generic automorphisms which are used to show the small index property. Truss 92 defines the notion of Truss generic automorphisms. We study the relationship between these two types of generic automorphisms.






- - - - Wednesday, Mar 23, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Joseph Dimos.

Date and Time:     Wednesday March 23, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Introduction to Fusion Categories and Some Applications.


Abstract: Tensor categories and multi-tensor categories have strong alignment with module categories. We can use the multi-tensor categories C in conjunction with classifying tensor algebras wrt C. From here, we can illustrate some examples of tensor categories: the category Vec of k-vector spaces that gives us a fusion category. This is defined as a category Rep(G) of some finite dimensional k-representations of a group G. From here, I will walk through the correspondence of tensor categories (Etingof) and fusion categories. Throughout, I will indicate a few unitary and non-unitary cases of fusion categories. Those unitary fusion categories are those that admit a uniquely monoidal structure. For example, this draws upon [Jones 1983] for finite index and finite depth that bridges a subfactor A-bimodule B to provide a full subcategory of some category A by its module structure. I will discuss some of these components throughout and explain the Morita equivalence of fusion categories.





- - - - Thursday, Mar 24, 2022 - - - -



- - - - Friday, Mar 25, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 25, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Vera Fischer, University of Vienna




Next Week in Logic at CUNY:

- - - - Monday, Mar 28, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 28, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Dongwoo Kim (CUNY).
Title: Necessity, Essence and Explanation

Abstract: I shall discuss some of the relations between metaphysical modality, essence and explanation. The essentialist approach to metaphysical modality seeks to give an account of necessity (and thus of possibility) as having its source in essence. But what is essence, and in what sense and how does it give rise to necessity? In their recent paper “Essential Properties are Super-Explanatory: Taming Metaphysical Modality” (2020), Marion Godman, Antonella Mallozzi and David Papineau have attempted to address these issues with respect to aposteriori necessities concerning kinds. According to their account, the essence of a kind consists in the super-explanatory property—a single property that is causally responsible for a multitude of commonalities shared by the instances of the kind. And they argue that this super-explanatory notion of essence offers a principled account of aposteriori necessities concerning kinds. In this talk, I am going to argue that their account is not satisfactory. I shall examine two main arguments of GMP that the super-explanatory property of a kind is metaphysically necessary and argue that they both are fallacious. Along the way, a general problem will emerge that applies to any account that tries to explicate the notion of essence in terms of an explanatory relation.





- - - - Tuesday, Mar 29, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 29, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Erez Shochat, St. Francis College



- - - - Wednesday, Mar 30, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Morgan Rogers, Universit`a degli Studi dell’Insubria.

Date and Time:     Wednesday March 30, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     TBA.




- - - - Thursday, Mar 31, 2022 - - - -



- - - - Friday, Apr 1, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 1, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Vera Fischer, University of Vienna






- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

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

Kamil Ryduchowski, Elementary submodels and infinitary combinatorics

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 22.03.2022, at 13.15, room 403 Speaker: Kamil Ryduchowski, (MIM UW) Title: Elementary submodels and infinitary combinatorics Abstact: "We will present techniques of using elementary submodels as a tool in infinitary combinatorics. We shall show short, elegant proofs of, among others, the Delta-system lemma, the pressing-down lemma, Erdos-Dushnik-Miller theorem." Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) Set Theory Research Seminar talk on Tuesday, March 22

Kurt Godel Research Center
Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 22 "A family of higher dimensional partition principles" Jeffrey Bergfalk (KGRC) This talk will be an exposition of the recent work \emph{A descriptive approach to higher derived limits}, joint with Nathaniel Bannister, Justin Moore, and Stevo Todorcevic (arXiv:2203.00165). The material of this paper is somewhat more ranging than its title would suggest. At its heart is a new family of partition principles which synthesize several recent advances in the study of higher derived limits, rendering those results far more amenable to combinatorial analyses. These principles admit formulation on any directed quasi-order, and are of particular, and interrelated, interest on the quasi-orders $({^\omega}\omega,\leq^*)$ and the ordinals $\omega_n$. A main implication of these principles in any case is the triviality of (higher dimensionally) coherent families of functions; we'll use any remaining time to note ways that such objects, and even higher derived limits, are closer to classical set theoretic concerns than perhaps tends to be realized. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universit?t Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 23rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Sam Braunfeld -- Monadic dividing lines and hereditary classes We will discuss how monadic versions of dividing lines in model theory (NIP, stability, NFCP) can be used to prove structure and non-structure results in hereditary classes, which can in turn be used for combinatorial applications. Best, David

Logic seminar Tuesday March 22

Carnegie Mellon Logic Seminar
TUESDAY, March 22, 2022 Mathematical logic seminar: 3:30 P.M., Online, Colin Jahel, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Asymptotic theories and homomorphically-avoided structures ABSTRACT: Given a class of finite structures, one can consider μn the uniform measure on structures in said class of size n. We study the asymptotic behavior, when n goes to infinity, of the family (μn)n. In particular, one can ask: which sentences have converging probability, and when is this limit non-zero? I will present our results for classes of graphs and digraphs, in particular classes not containing any homorphic copies of certain sets of finite structures. Joint work with Manuel Bodirsky.

Logic Seminar 16 March 2022 16:00 hrs SGT by Leszek Kolodziejcyk, University of Warsaw

NUS Logic Seminar
Hello, there were various typing errors in the announcement of today's talk including an error of the timing in the email subject. Therefore I resend the announcement. Best regards, Frank Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Leszek Kolodziejczyk Title: A conservativity result for not-WO(omega^omega) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The Chong-Slaman-Yang construction of a model of RT^2_2 not satisfying Sigma^0_2-induction makes crucial use of a principle known as BME_1. This principle was later shown by Kreuzer and Yokoyama to be equivalent to WO(omega^omega), the statement that omega^omega is well-ordered. I will talk about the following result: if A is any set in a model of RCA_0 + Sigma^0_2-collection such that Sigma_2(A)-induction fails, then there is a descending sequence in omega^omega that is low in A. As a consequence, the negation of WO(omega^omega) is Pi11-conservative over RCA_0 + BSigma^0_2 + not-ISigma^0_2. This result has some potentially interesting corollaries: - If RCA_0 + RT^2_2 is Pi^1_1-conservative over BSigma^0_2, then this can be proved by considering only models in which BME_1 fails. - The formula "X is a well-order" is not provably equivalent to any Sigma^1_1 formula over COH + BSigma^0_2 + not-ISigma^0_2. (In contrast, by earlier work of Fiori Carones, Wong, Yokoyama, and myself, the theory WKL*_0 + not-ISigma^0_1, which is to some extent analogous to COH + BSigma^0_2 + not-ISigma^0_2, proves a collapse of the analytic hierarchy to Delta^1_1.) - There exist two models of RCA_0 + COH + BSigma^0_2 that share a first-order universe and a common counterexample to ISigma^0_2 but are not elementarily equivalent. (In contrast, by the work of Fiori Carones et al. mentioned above, the families of Delta^0_2-definable sets of any such two models have to be elementarily equivalent.) The conservativity result is a side product of a larger project joint with Fiori Carones, Yokoyama, and others.

Gruesse aus Singapur

NUS Logic Seminar
Hello, there were various typing errors in the announcement of today's talk including an error of the timing in the email subject. Therefore I resend the announcement. Best regards, Frank Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Leszek Kolodziejczyk Title: A conservativity result for not-WO(omega^omega) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The Chong-Slaman-Yang construction of a model of RT^2_2 not satisfying Sigma^0_2-induction makes crucial use of a principle known as BME_1. This principle was later shown by Kreuzer and Yokoyama to be equivalent to WO(omega^omega), the statement that omega^omega is well-ordered. I will talk about the following result: if A is any set in a model of RCA_0 + Sigma^0_2-collection such that Sigma_2(A)-induction fails, then there is a descending sequence in omega^omega that is low in A. As a consequence, the negation of WO(omega^omega) is Pi11-conservative over RCA_0 + BSigma^0_2 + not-ISigma^0_2. This result has some potentially interesting corollaries: - If RCA_0 + RT^2_2 is Pi^1_1-conservative over BSigma^0_2, then this can be proved by considering only models in which BME_1 fails. - The formula "X is a well-order" is not provably equivalent to any Sigma^1_1 formula over COH + BSigma^0_2 + not-ISigma^0_2. (In contrast, by earlier work of Fiori Carones, Wong, Yokoyama, and myself, the theory WKL*_0 + not-ISigma^0_1, which is to some extent analogous to COH + BSigma^0_2 + not-ISigma^0_2, proves a collapse of the analytic hierarchy to Delta^1_1.) - There exist two models of RCA_0 + COH + BSigma^0_2 that share a first-order universe and a common counterexample to ISigma^0_2 but are not elementarily equivalent. (In contrast, by the work of Fiori Carones et al. mentioned above, the families of Delta^0_2-definable sets of any such two models have to be elementarily equivalent.) The conservativity result is a side product of a larger project joint with Fiori Carones, Yokoyama, and others.

Cross-Alps Logic Seminar (speaker: Damir Dzhafarov)

Cross-Alps Logic Seminar
On Friday 18.03.2022 at 16:00

Damir Dzhafarov (University of Connecticut)

will give a talk on

The SRT22 vs. COH problem

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 2017 'Mathematical logic: models, sets, computability'.



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This Week in Logic at CUNY

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

- - - - Monday, Mar 14, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 14, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Wilfrid Hodges (King’s)
Title: Avicenna motivates two new logics

Abstract: The logician Avicenna (Ibn Sina in Arabic) tells us that some thousand and twenty years ago he discovered a group of previously unknown logics. He seems to have been the first logician – at least west of India and after the ancient Greeks – who made any such claim. We will examine two of these new logics and his motivations for them. The first new logic, discovered in around 994 when Avicenna was about eighteen years old, was rediscovered by Boole in the mid 19th century. We will study some features of it that were important to Avicenna (and to some recent logicians) but apparently missed by Boole. The second new logic, probably from around 1000, seems to be the earliest logic with inference rules that act below the surface levels of the formulas. It was impossible to state the inference rules correctly before Frege introduced the notion of scope, but we will see how far Avicenna got.



- - - - Tuesday, Mar 15, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 15, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Thomas Ferguson, University of Amsterdam and University of St. Andrews

Models of Relevant Arithmetic

In the 1970s, the logician and philosopher Robert Meyer proposed a novel response to Goedel's Incompleteness Theorems, suggesting that perhaps the results' impact could be blunted by analyzing Peano arithmetic with a weaker deductive system. Initial successes of the program of relevant arithmetic were positive. E.g., R# (the theory of Peano arithmetic under the relevant logic R) can be shown consistent in the sense of not proving 0=1 and this can be shown through arguably finitistic methods. In this talk I will discuss the rise and fall of Meyer's program, detailing the philosophical foundations, its positive development, and the context of Harvey Friedman's negative result in 1992. I'll also suggest why the program, although not necessarily successful, is nevertheless an interesting object of study.

Also note that a great deal of context—including Meyer's two long-unpublished monographs on the topic—have recently appeared in a special issue of the Australasian Journal of Logic I co-edited with Graham Priest, which can be found at https://ojs.victoria.ac.nz/ajl/issue/view/751.



- - - - Wednesday, Mar 16, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Jin-Cheng Guu, Stony Brook University.
Date and Time:     Wednesday March 16, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Topological Quantum Field Theories from Monoidal Categories.

Abstract: We will introduce the notion of a topological quantum field theory (tqft) and a monoidal category. We will then construct a few (extended) tqfts from monoidal categories, and show how quantum invariants of knots and 3-manifolds were obtained. If time permits, I will discuss (higher) values in (higher) codimensions based on my recent work on categorical center of higher genera (joint with A. Kirillov and Y. H. Tham).



- - - - Thursday, Mar 17, 2022 - - - -



- - - - Friday, Mar 18, 2022 - - - -


Next Week in Logic at CUNY:

- - - - Monday, Mar 21, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 21, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Noson Yanofsky (CUNY)
Title: Why Mathematics Works so Well

Abstract: A major question in philosophy of science involves the unreasonable effectiveness of mathematics in physics. Why should mathematics, created or discovered, with nothing empirical in mind be so perfectly suited to describe the laws of the physical universe? To answer this, we review the well-known fact that the defining properties of the laws of physics are their symmetries. We then show that there are similar symmetries of mathematical facts and that these symmetries are the defining properties of mathematics. By examining the symmetries of physics and mathematics, we show that the effectiveness is actually quite reasonable. In essence, we show that the regularities of physics are a subset of the regularities of mathematics.



- - - - Tuesday, Mar 22, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 22, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Ermek Nurkhaidarov, Penn State Mont Alto



- - - - Wednesday, Mar 23, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Joseph Dimos.

Date and Time:     Wednesday March 23, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Introduction to Fusion Categories and Some Applications.


Abstract: Tensor categories and multi-tensor categories have strong alignment with module categories. We can use the multi-tensor categories C in conjunction with classifying tensor algebras wrt C. From here, we can illustrate some examples of tensor categories: the category Vec of k-vector spaces that gives us a fusion category. This is defined as a category Rep(G) of some finite dimensional k-representations of a group G. From here, I will walk through the correspondence of tensor categories (Etingof) and fusion categories. Throughout, I will indicate a few unitary and non-unitary cases of fusion categories. Those unitary fusion categories are those that admit a uniquely monoidal structure. For example, this draws upon [Jones 1983] for finite index and finite depth that bridges a subfactor A-bimodule B to provide a full subcategory of some category A by its module structure. I will discuss some of these components throughout and explain the Morita equivalence of fusion categories.





- - - - Thursday, Mar 24, 2022 - - - -



- - - - Friday, Mar 25, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 25, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Vera Fischer, University of Vienna




- - - - Other Logic News - - - -



- - - - Web Site - - - -

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Jakub Andruszkiewicz, The club principle and its connections to the diamond principle

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 15.03.2022, at 13.15, room 403 Speaker: Jakub Andruszkiewicz, (UW/IM PAN) Title: The club principle and its connections to the diamond principle Abstact: The club principle was first introduced by Ostaszewski as a weakening of the diamond principle, as it plays a crucial role in his original construction of the Ostaszewski space. It is well-known that under CH those principles are equivalent and we will present a proof of this fact. We will also show by using an appropriate forcing extension that, as proven by Shelah, assuming CH is essential, i.e. it is consistent relative to ZFC that the club principle holds while the diamond principle does not. Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) seminar talks Tuesday, March 15 and Thursday, March 17

Kurt Godel Research Center
Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 15 "Forcing the \Pi^1_n-uniformization property" Stefan Hoffelner (University of M?nster, Germany) The uniformization property, introduced by N. Lusin in 1930, is an extensively studied notion in descriptive set theory. For a given projective pointclass $\Gamma$ it says that every subset of the plane which belongs to $\Gamma$ has a uniformizing function whose graph is an element of $\Gamma$ as well. The celebrated results of Y. Moschovakis on the one hand and D. Martin, J. Steel and H. Woodin on the other, yield a natural and global description of the behaviour of the uniformization property for projective pointclasses under the assumption of large cardinals. In particular, under PD, for every natural number n, $\Pi^1_{2n+1}$-sets and hence $\Sigma^1_{2n+2}$-sets do have the uniformization property. Yet the question of universes which display an alternative behaviour of theses regularity properties has remained in large parts a complete mystery, mostly due to the absence of forcing techniques to produce such models. Consequentially, a lot of very natural problems have remained wide open ever since. In my talk, I want to outline some recently obtained tools, which turn the question of forcing a universe with the $\Pi^1_n$-uniformization property into a fixed point problem for certain sets of forcing notions. This fixed point problem can be solved, yielding a specific set of forcing notions which in turn can be used to force the Uniformization property (for n>2) over fine structural inner models with large cardinals (for n=3, the inner model is just L). For even n, these universes witness for the first time the consistency (relative to the existence of n-3 many Woodin cardinals) of the $\Pi^1_{n}$-uniformization property, and, for odd n, give new lower bounds in terms of consistency strength. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universit?t Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt G?del Research Center Thursday, March 17 "Forcing and the Separation, the Reduction and the Uniformization Property" Stefan Hoffelner (University of M?nster, Germany) The Separation property, the Reduction property and the Uniformization property, introduced in the 1920's and 1930's are three classical regularity properties of pointclasses of the reals. The celebrated results of Y. Moschovakis on the one hand and D. Martin, J. Steel and H. Woodin on the other, yield a global description of the behaviour of these regularity properties for projective pointclasses under the assumption of large cardinals. These results, impressive as they are, still leave open a lot of natural questions. To name a few we mention: Do we need large cardinals to obtain their effects on the behaviour of these regularity property? Is the $\Sigma^1_{2n+1}$-separation property actually consistent for n >1? More generally: to what extent can we produce set theoretic universes which display a different behaviour of these regularity properties? Are the separation the reduction and the uniformization property different notions at all? The goal of this talk to introduce the three mentioned regularity properties, present a couple of these natural problems and discuss new results, utilising a novel forcing technique, which answer some of them. Time and Place Talk at 3:00pm Universit?t Wien Institut f?r Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 16th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Uhrik -- The effect of MA on graphs on omega_1 I'll talk about Todorcevic's result that MA_omega1 implies that every graph on omega_1 without an uncountable independent set contains a clique of ordertype omega^2. Best, David

Logic Seminar 16 March 2022 17:00 hrs at NUS by Leszek Kolodziejczyk

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Leszek Kolodziejczyk Title: A conservativity result for not-WO(omega^omega) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The Chong-Slaman-Young construction of a model of RT^2_2 not satisfying Sigma^0_2-induction makes crucial use of a principle known as BME_1. This principle was later shown by Kreuzer and Yokoyama to be equivalent to WO(omega^omega), the statement that omega^omega is well-ordered. I will talk about the following result: if A is any set in a model of RCA_0 + Sigma^0_2-collection such that Sigma_2(A)-induction fails, then there is a descending sequence in omega^omega that is low in A. As a consequence, the negation of WO(omega^omega) is Pi11-conservative over RCA_0 + BSigma^0_2 + not-ISigma^0_2. This result has some potentially interesting corollaries: - If RCA_0 + RT^2_2 is Pi^1_1-conservative over BSigma^0_2, then this can be proved by considering only models in which BME_1 fails. - The formula "X is a well-order" is not provably equivalent to any Sigma^1_1 formula over COH + BSigma^0_2 + not-ISigma^0_2. (In contrast, by earlier work of Fiori Carones, Wong, Yokoyama, and myself, the theory WKL*_0 + not-ISigma^0_1, which is to some extent analogous to COH + BSigma^0_2 + not-ISigma^0_2, proves a collapse of the analytic hierarchy to Delta^1_1.) - There exist two models of RCA_0 + COH + BSigma^0_2 that share a first-order universe and a common counterexample to ISigma^0_2 but are not elementarily equivalent. (In contrast, by the work of Fiori Carones et al. mentioned above, the families of Delta^0_2-definable sets of any such two models have to be elementarily equivalent.) The conservativity result is a side product of a larger project joint with Fiori Carones, Yokoyama, and others.

Logic Seminar 16 March 2022 17:00 hrs at NUS by Leszek Kolodziejczyk

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Leszek Kolodziejczyk Title: A conservativity result for not-WO(omega^omega) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The Chong-Slaman-Young construction of a model of RT^2_2 not satisfying Sigma^0_2-induction makes crucial use of a principle known as BME_1. This principle was later shown by Kreuzer and Yokoyama to be equivalent to WO(omega^omega), the statement that omega^omega is well-ordered. I will talk about the following result: if A is any set in a model of RCA_0 + Sigma^0_2-collection such that Sigma_2(A)-induction fails, then there is a descending sequence in omega^omega that is low in A. As a consequence, the negation of WO(omega^omega) is Pi11-conservative over RCA_0 + BSigma^0_2 + not-ISigma^0_2. This result has some potentially interesting corollaries: - If RCA_0 + RT^2_2 is Pi^1_1-conservative over BSigma^0_2, then this can be proved by considering only models in which BME_1 fails. - The formula "X is a well-order" is not provably equivalent to any Sigma^1_1 formula over COH + BSigma^0_2 + not-ISigma^0_2. (In contrast, by earlier work of Fiori Carones, Wong, Yokoyama, and myself, the theory WKL*_0 + not-ISigma^0_1, which is to some extent analogous to COH + BSigma^0_2 + not-ISigma^0_2, proves a collapse of the analytic hierarchy to Delta^1_1.) - There exist two models of RCA_0 + COH + BSigma^0_2 that share a first-order universe and a common counterexample to ISigma^0_2 but are not elementarily equivalent. (In contrast, by the work of Fiori Carones et al. mentioned above, the families of Delta^0_2-definable sets of any such two models have to be elementarily equivalent.) The conservativity result is a side product of a larger project joint with Fiori Carones, Yokoyama, and others.

Cross-Alps Logic Seminar (speaker: Alessandro Andretta)

Cross-Alps Logic Seminar
On Friday 11.03.2022 at 16:00

Alessandro Andretta (University of Turin)

will give a talk on

Sierpinski’s partitions with Sigma^1_2 pieces

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] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.


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This Week in Logic at CUNY

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

- - - - Monday, Mar 7, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 7, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
David Papineau (King’s).
Title: Understanding Causal Inference

Abstract: The current pandemic has focused attention on the techniques used by epidemiologists and other non-experimental scientists to infer causal hypotheses from correlational data. These techniques, which hinge on assumptions about the way causal connections manifest themselves in conditional and unconditional correlations, pose an obvious philosophical challenge. What is it about causation that allows them to work? None of the mainstream accounts of causation—counterfactual, process, dispositional, regularity—casts any light on this question. Probabilistic and interventionist theories of causation do offer a direct response to the challenge, by positing a constitutive connection between causes and correlations, but I shall argue that these theories do not dig deep enough. Instead I shall develop an older idea—which goes back to H.A. Simon in the 1950s—that relates causal relationships to systems of structural equations with probabilistically independent exogenous variables. The attraction of this structural equations approach is that it allows us to view the correlational patterns as fallible evidence for causal relationships, rather than constitutive of them. I shall consider whether this approach can lead to a full reduction of causation and how it might accommodate quantum mechanical unpredictability.





- - - - Tuesday, Mar 8, 2022 - - - -



- - - - Wednesday, Mar 9, 2022 - - - -



- - - - Thursday, Mar 10, 2022 - - - -



- - - - Friday, Mar 11, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 11, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University



Logic Workshop
CUNY Graduate Center, Friday, March 11, 2pm
The seminar will take place at the CUNY Graduate Center at 2pm in Room TBA.

Joel David Hamkins, Notre Dame University
Infinite wordle and the mastermind numbers

I shall introduce and consider the natural infinitary variations of Wordle, Absurdle, and Mastermind. Infinite Wordle extends the familiar finite game to infinite words and transfinite play—the code-breaker aims to discover a hidden codeword selected from a dictionary  of infinite words over a countable alphabet  by making a sequence of successive guesswords, receiving feedback after each guess concerning its accuracy. For any dictionary using the usual 26-letter alphabet, for example, the code-breaker can win in at most 26 guesses, and more generally in  guesses for alphabets of finite size . Meanwhile, for some dictionaries on an infinite alphabet, infinite play is required, but the code-breaker can always win by stage  on a countable alphabet, for any fixed dictionary. Infinite Mastermind, in contrast, is a subtler game than Wordle because only the number and not the position of correct bits is given. When duplication of colors is allowed, nevertheless, then the code-breaker can still always win by stage , but in the no-duplication variation, no countable number of guesses (even transfinite) is sufficient for the code-breaker to win. I therefore introduce the mastermind number, denoted , to be the size of the smallest winning no-duplication Mastermind guessing set, a new cardinal characteristic of the continuum, which I prove is bounded below by the additivity number  of the meager ideal and bounded above by the covering number . In particular, the precise value of the mastermind number is independent of ZFC and can consistently be strictly between  and the continuum . In simplified Mastermind, where the feedback given at each stage includes only the numbers of correct and incorrect bits (omitting information about rearrangements), then the corresponding simplified mastermind number is exactly the eventually different number http://jdh.hamkins.org/infinite-wordle-and-the-mastermind-numbers-cuny-logic-workshop-march-2022/




Next Week in Logic at CUNY:

- - - - Monday, Mar 14, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 14, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Wilfrid Hodges (King’s)
Title: Avicenna motivates two new logics

Abstract: The logician Avicenna (Ibn Sina in Arabic) tells us that some thousand and twenty years ago he discovered a group of previously unknown logics. He seems to have been the first logician – at least west of India and after the ancient Greeks – who made any such claim. We will examine two of these new logics and his motivations for them. The first new logic, discovered in around 994 when Avicenna was about eighteen years old, was rediscovered by Boole in the mid 19th century. We will study some features of it that were important to Avicenna (and to some recent logicians) but apparently missed by Boole. The second new logic, probably from around 1000, seems to be the earliest logic with inference rules that act below the surface levels of the formulas. It was impossible to state the inference rules correctly before Frege introduced the notion of scope, but we will see how far Avicenna got.



- - - - Tuesday, Mar 15, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 15, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Models of Relevant Arithmetic
Thomas Ferguson University of Amsterdam and University of St. Andrews



- - - - Wednesday, Mar 16, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Jin-Cheng Guu, Stony Brook University.
Date and Time:     Wednesday March 16, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Topological Quantum Field Theories from Monoidal Categories.

Abstract: We will introduce the notion of a topological quantum field theory (tqft) and a monoidal category. We will then construct a few (extended) tqfts from monoidal categories, and show how quantum invariants of knots and 3-manifolds were obtained. If time permits, I will discuss (higher) values in (higher) codimensions based on my recent work on categorical center of higher genera (joint with A. Kirillov and Y. H. Tham).



- - - - Thursday, Mar 17, 2022 - - - -



- - - - Friday, Mar 18, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 18, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University



- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

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CMU math logic seminar on Tuesday, March 15

Carnegie Mellon Logic Seminar
TUESDAY, March 15, 2022 Mathematical logic seminar: 3:30 P.M., Online, Alex Kruckman, Wesleyan University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Properly ergodic structures ABSTRACT: One natural notion of "random (countably infinite) L-structure" is a probability measure on the space of L-structures with domain omega which is invariant and ergodic for the natural action of the symmetric group Sym(omega) on this space. We call such a measure an ergodic structure. The most famous example of an ergodic structure is the Erdős–Rényi random graph model on domain omega, which gives measure 1 to the isomorphism type of the Rado graph. Ergodic structures also arise naturally as limits of sequences of finite structures which are convergent in the appropriate sense, generalizing the graph limits of Lovász and Szegedy. Some ergodic structures (like the Erdős–Rényi random graph model) are almost surely isomorphic to a single countable structure (like the Rado graph), and the countable structures which arise in this way have been completely characterized by Ackerman, Freer, and Patel. In this talk, we will consider properly ergodic structures, those which do not give measure 1 to any single isomorphism type. What do properly ergodic models "look like"? To address this question, we develop an analogue of the Scott rank for ergodic structures, which leads to a precise characterization of those first-order theories (and, more generally, those sentences of the infinitary logic L_{omega_1,omega}) which admit properly ergodic models. This is joint work with Ackerman, Freer, and Patel.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 9th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Higher-dimensional coherent Aronszajn trees We will introduce a family of higher-dimensional analogues of coherent Aronszajn trees arising from a cohomological analysis of ordinals, considered as topological spaces with the order topology. We will investigate the influence of large cardinals on the existence of such higher-dimensional coherent Aronszajn trees and will prove that, if V=L, then these higher-dimensional coherent Aronszajn trees exist everywhere except where ruled out for trivial reasons. We will also present some interesting open questions. This is joint work with Jeffrey Bergfalk. Best, David

(KGRC) seminar talks Tuesday, March 8 and Thursday, March 10

Kurt Godel Research Center
The KGRC welcomes as guests: Jonathan Cancino (host: Vera Fischer) visits the KGRC from March 7 to March 11 and give a talk (see below). Piotr Borodulin-Nadzieja (host: Damian Sobota) visits the KGRC from March 9 to March 13. * * * Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 8 "There may be no I-ultrafilters for any F_\sigma ideal I" Jonathan Cancino (Czech Academy of Sciences, Czech Republic) Given an ideal I and an ultrafilter U, both on \omega, we say that U is an I-ultrafilter if for any f:\omega\to\omega there is A\in U such that f[A]\in I. This notion was introduced by J. Baumgartner in 1995, and it has proved to be very useful in the classification of combinatorial properties of ultrafilters. In particular, the notion of Hausdorff ultrafilter is codify as being G_fc-ultrafilter, where G_fc denotes the ideal of finite chromatic graphs on. We will prove that consistently there is no I-ultrafilter for any F_\sigma ideal I. Since the ideal G_fc is an F_\sigma ideal, our result implies that consistently there is no Hausdorff ultrafilter. This answers a question of M. Di Nasso and M. Forti, among several other questions about the existence of I-ultrafilters. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universit?t Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt G?del Research Center Thursday, March 10 "The Interplay of Determinacy, Large Cardinals, and Inner Models" Sandra M?ller (TU Wien) The standard axioms of set theory, Zermelo-Fraenkel set theory with Choice (ZFC), do not suffice to answer all questions in mathematics. While this follows abstractly from Kurt G?del's famous incompleteness theorems, we nowadays know numerous concrete examples for such questions. In addition to a large number of problems in set theory, even many problems outside of set theory have been showed to be unsolvable, meaning neither their truth nor their failure can be proven from ZFC. A major part of set theory is devoted to attacking this problem by studying various extensions of ZFC and their properties with the overall goal to identify the "right" axioms for mathematics that settle these problems. Determinacy assumptions are canonical extensions of ZFC that postulate the existence of winning strategies in natural infinite two-player games. Such assumptions are known to enhance sets of real numbers with a great deal of canonical structure. Other natural and well-studied extensions of ZFC are given by the hierarchy of large cardinal axioms. Inner model theory provides canonical models for many large cardinal axioms. Determinacy assumptions, large cardinal axioms, and their consequences are widely used and have many fruitful implications in set theory and even in other areas of mathematics. Many applications, in particular, proofs of consistency strength lower bounds, exploit the interplay of determinacy axioms, large cardinals, and inner models. In this talk I will survey recent developments as well as my contribution to this flourishing area. Time and Place Talk at 3:00pm Universit?t Wien Institut f?r Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

Cross-Alps Logic Seminar (speaker: Michal Skrzypczak)

Cross-Alps Logic Seminar
Dear all,

On Friday 04.03.2022 at 16:00

Michal Skrzypczak (University of Warsaw)

will give a talk on

The infinite tree - from Kolmogorov, Rabin, and Shelah to modern Theoretical Computer Science

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. Here are the information to access the meeting:

ACCESS TO WEBEX MEETING

Link Meeting
Number Meeting: 2733 686 2768
Password: ErDGYCdk795

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Luca

--
We sent you this email because you are in the mailing list of Cross-Alps Logic Seminar.
If you do not want to receive our seminar announcements anymore, please write to luca.mottoros@unito.it.

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This Week in Logic at CUNY

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

- - - - Monday, Feb 28, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 28, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Michael Burton (Yale).
Title: Paraconsistency with some detachment

Abstract: In this talk, a proof-of-concept logic is presented that is like first-order LP (the “logic of paradox”) except things behave classically within the scope of universal quantifiers. This logic’s material conditional does not, in general, detach, but much can be deduced with it. Structures for this logic are classical first-order structures equipped with a congruence relation, giving this logic a connection to Priest’s collapsing lemma for LP. Some possible improvements to this logic are then discussed. One of these involves separating classicality from universal quantification, having classicality be mediated instead by operators that interact with variable assignments. Finally, the relevance of logics of this kind to various logical paradoxes is discussed.





- - - - Tuesday, Mar 1, 2022 - - - -



- - - - Wednesday, Mar 2, 2022 - - - -



- - - - Thursday, Mar 3, 2022 - - - -



- - - - Friday, Mar 4, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 4, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Tom Benhamou, Tel Aviv University
Subforcings of the Tree-Prikry Forcing

We investigate which forcing notions can be embedded into a Tree-Prikry forcing. It turns out that the answer changes drastically under different large cardinal assumptions. We will focus on the class of strategically closed forcings of cardinality strategically closed forcings of cardinality  and the distributive forcing notions of cardinality . Then we will examine distributive subforcings of the Prikry forcing of cardinality larger than . This is a joint work with Moti Gitik and Yair Hayut.



Next Week in Logic at CUNY:

- - - - Monday, Mar 7, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 7, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
David Papineau (King’s).
Title: Understanding Causal Inference

Abstract: The current pandemic has focused attention on the techniques used by epidemiologists and other non-experimental scientists to infer causal hypotheses from correlational data. These techniques, which hinge on assumptions about the way causal connections manifest themselves in conditional and unconditional correlations, pose an obvious philosophical challenge. What is it about causation that allows them to work? None of the mainstream accounts of causation—counterfactual, process, dispositional, regularity—casts any light on this question. Probabilistic and interventionist theories of causation do offer a direct response to the challenge, by positing a constitutive connection between causes and correlations, but I shall argue that these theories do not dig deep enough. Instead I shall develop an older idea—which goes back to H.A. Simon in the 1950s—that relates causal relationships to systems of structural equations with probabilistically independent exogenous variables. The attraction of this structural equations approach is that it allows us to view the correlational patterns as fallible evidence for causal relationships, rather than constitutive of them. I shall consider whether this approach can lead to a full reduction of causation and how it might accommodate quantum mechanical unpredictability.





- - - - Tuesday, Mar 8, 2022 - - - -



- - - - Wednesday, Mar 9, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Jin-Cheng Guu, Stony Brook University.
Date and Time:     Wednesday March 9, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Topological Quantum Field Theories from Monoidal Categories.

Abstract: We will introduce the notion of a topological quantum field theory (tqft) and a monoidal category. We will then construct a few (extended) tqfts from monoidal categories, and show how quantum invariants of knots and 3-manifolds were obtained. If time permits, I will discuss (higher) values in (higher) codimensions based on my recent work on categorical center of higher genera (joint with A. Kirillov and Y. H. Tham).





- - - - Thursday, Mar 10, 2022 - - - -



- - - - Friday, Mar 11, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 11, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University



Logic Workshop
CUNY Graduate Center, Friday, March 11, 2pm
The seminar will take place at the CUNY Graduate Center at 2pm in Room TBA.

Joel David Hamkins, Notre Dame University
Infinite wordle and the mastermind numbers

I shall introduce and consider the natural infinitary variations of Wordle, Absurdle, and Mastermind. Infinite Wordle extends the familiar finite game to infinite words and transfinite play—the code-breaker aims to discover a hidden codeword selected from a dictionary  of infinite words over a countable alphabet  by making a sequence of successive guesswords, receiving feedback after each guess concerning its accuracy. For any dictionary using the usual 26-letter alphabet, for example, the code-breaker can win in at most 26 guesses, and more generally in  guesses for alphabets of finite size . Meanwhile, for some dictionaries on an infinite alphabet, infinite play is required, but the code-breaker can always win by stage  on a countable alphabet, for any fixed dictionary. Infinite Mastermind, in contrast, is a subtler game than Wordle because only the number and not the position of correct bits is given. When duplication of colors is allowed, nevertheless, then the code-breaker can still always win by stage , but in the no-duplication variation, no countable number of guesses (even transfinite) is sufficient for the code-breaker to win. I therefore introduce the mastermind number, denoted , to be the size of the smallest winning no-duplication Mastermind guessing set, a new cardinal characteristic of the continuum, which I prove is bounded below by the additivity number  of the meager ideal and bounded above by the covering number . In particular, the precise value of the mastermind number is independent of ZFC and can consistently be strictly between  and the continuum . In simplified Mastermind, where the feedback given at each stage includes only the numbers of correct and incorrect bits (omitting information about rearrangements), then the corresponding simplified mastermind number is exactly the eventually different number http://jdh.hamkins.org/infinite-wordle-and-the-mastermind-numbers-cuny-logic-workshop-march-2022/





- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 2nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Noé de Rancourt -- On countable unions of Borel equivalence relations I'll talk about dichotomies of Borel equivalence relations obtained with Benjamin Miller which characterize the obstructions for an equivalence relation to be in a given complexity class F assuming we know it is a countable union of relations from F. Our simplest result is in some sense an extension of Kechris-Louveau's E_1-dichotomy. There will be no proofs, because those are way too long. Best, David

European Set Theory Conference: 29 August - 2 September 2022

Conference
EUROPEAN SET THEORY CONFERENCE 2022 August 29th-September 2nd, 2022 Turin, Italy We are pleased to announce that the registration for the ESTC2022 is now open! (See below for the relevant deadlines.) Various forms of financial support for young researchers are available. It is also possible to submit a title and abstract for a contributed talk; submissions will be evaluated by the Scientific Committee, and a decision will be communicated 2-3 months before the conference. Please visit our website or contact us through this form for more information. The conference will be held in person, we are confident that at the end of the summer the pandemic situation will be under control. It will be nice to meet in person again, after these challenging years. Also, it is a very good season to visit Turin, a beautiful city in northern Italy, while attending one of the most exciting conferences in set theory! If you are interested, please register as soon as possible, and do not forget to submit your title and abstract if you want to contribute with a short talk. We also kindly ask you to share this announcement with all people who might be interested in the event. IMPORTANT DEADLINES: 30/04/2022: Abstract submission for contributed talks 30/06/2022: Early registration with reduced fee 22/08/2022: Registration MORE ON THE CONFERENCE: The European Set Theory Conferences is a series of biannual meetings coordinated by the European Set Theory Society (ESTS). This year's edition is organized by the Department of Mathematics of the University of Turin and ESTS, in partnership with the Clay Mathematics Institute. It is the most important conference in set theory, and gathers the worldwide leaders in the field as well as many young researchers. During the event, the prestigious Hausdorff medal will be awarded for the most influential work in set theory published in the preceding five years. There will also be a special session in honor of Boban Veličković's 60th birthday. Invited speakers - Jeffrey Bergfalk (Vienna) - Filippo Calderoni (Chicago) - Natasha Dobrinen (Denver) - Osvaldo Guzmán (Mexico) - Joel Hamkins (Notre Dame) - Chris Lambie-Hanson (Prague) - Martino Lupini (New Zealand) - Julien Melleray (Lyon) - Andrew Marks (UCLA) - Sandra Müller (Vienna) - Saharon Shelah (Jerusalem) - Stevo Todorčević (Toronto and Paris) - Jouko Väänänen (Helsinki) - Zoltán Vidnyánsky (Caltech) - Trevor Wilson (Miami) Tutorials - Yair Hayut (Jerusalem) - Grigor Sargsyan (Poland) Boban Veličković's 60th Birthday Celebration - Laura Fontanella (Paris) - Rahman Mohammadpour (Vienna) - Giorgio Venturi (Brasil) - Matteo Viale (Turin) Scientific committee Joan Bagaria (chair), Matthew Foreman, Moti Gitik, Péter Komjáth, Piotr Koszmider, Heike Mildenberger, Luca Motto Ros, John Steel Local organizing committee Alessandro Andretta, Raphaël Carroy, Luca Motto Ros, Gianluca Paolini, Francesco Parente, Salvatore Scamperti, Matteo Viale
Link to more info

Logic Seminar Wed 2 March 2022 16:00 hrs at NUS by Lavinia Picollo

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 2 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Lavinia Picollo, NUS Title: High-order logic and disquotational truth URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Truth predicates are widely believed to be capable of serving a certain logical or quasi-logical function. There is little consensus, however, on the exact nature of this function. We offer a series of formal results in support of the thesis that disquotational truth is a device to simulate higher-order resources in a first-order setting. More specifically, we show that any theory formulated in a higher-order language can be naturally and conservatively interpreted in a first-order theory with a disquotational truth or truth-of predicate. In the first part of the talk we focus on the relation between truth and full impredicative sentential quantification. The second part is devoted to the relation between truth-of and full impredicative predicate quantification. This is joint work with Thomas Schindler

(KGRC) Set Theory Seminar talk on Tuesday, March 1

Kurt Godel Research Center
The KGRC welcomes as guests: Sarka Stejskalova and Radek Honzik (host: Sy-David Friedman) visit the KGRC until February 28. * * * Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 1 "Ramsey Theory of Ordinals and Finite Combinatorics" Thilo Weinert (KGRC) The Ramsey Theory of Ordinals has been investigated over the last decades and a large variety of results have been attained. The talk is going to focus on the Ramsey Theory of finite multiples both of infinite cardinals and, in some cases products of two infinite cardinals. This leads to problems in finite combinatorics similar to the calculation of finite Ramsey numbers. On the one hand, exact results are usually only obtainable if the natural numbers involved remain somewhat small. On the other hand, sometimes asymptotic results can be attained. More concretely, for any ordinal $\alpha$ and $\beta$, let $r(\alpha, \beta)$ denote the least ordinal $\gamma$ such that any colouring of the pairs in $\gamma$ in black and white either allows for a homogeneously white subset of order-type $\alpha$ or a homogeneously black subset of order-type $\beta$. Since the nineties it is known that the growth of $r(n, 3)$ is of order $n^2/log(n)$. It turns out that for any infinite cardinal $\lambda$, we have $r(\lambda * n, 3) = \lambda * r(I_n, L_3)$ where the growth of $r(I_n, L_3)$ is of order $n^2/log(n)$ as well. Similarly, if $\kappa > \lambda$ is weakly compact, we have $r(\kappa * \lambda * n, 3) = \kappa * \lambda * r(I_n, S_3) where, again, the growth of $r(I_n, L_3)$ is of order $n^2/log(n)$. Finally there is a finitary characterisation of the Ramsey numbers $r(\omega^2 *n, k)$ for natural numbers $n$ and $k$. However the growth behaviour of $r(\omega^2 * n, 3)$ is still unknown. This is partly joint work with Ferdinand Ihringer and Deepak Rajendraprasad. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universitt Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 2nd floor Seminar room 10 Talk at 3:00pm -- if you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt G?del Research Center Please note that Sandra M?llers talk had to be rescheduled to March 10.

Two CMU seminars next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, March 1, 2022 Mathematical logic seminar: 3:30 P.M., Online, Aristotelis Panagiotopoulos, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Every CBER is smooth below a Milliken-generic strong subtree (Part I) ABSTRACT: The theory of Borel reductions becomes a very delicate subject of study when one restricts attention to the class of Countable Borel Equivalence Relations (CBERs). Indeed, no matter how complex a CBER is, its complexity tends to reside on a "small" piece of its domain. For example a result of Hjorth and Kechris states that every CBER on a Polish space is hyperfinite when restricted to some comeager set. Similarly, classical results of Mathias about forcing extensions by Mathias reals imply that every CBER on the Ellentuck Ramsey space is hyperfinite when restricted to some pure Ellentuck cube. In this talk we show that the Milliken space M of strong trees satisfies a much stronger canonization property: if E is CBER on M then for the Milliken-generic T in M we have that E and = agree on the pure Milliken cube [T]. This is joint work with Allison Wang. TUESDAY, March 1, 2022 Set theory reading group: 4:30 P.M., Online, Allison Wang, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Every CBER is smooth below a Milliken-generic strong subtree (Part II) ABSTRACT: The theory of Borel reductions becomes a very delicate subject of study when one restricts attention to the class of Countable Borel Equivalence Relations (CBERs). Indeed, no matter how complex a CBER is, its complexity tends to reside on a "small" piece of its domain. For example a result of Hjorth and Kechris states that every CBER on a Polish space is hyperfinite when restricted to some comeager set. Similarly, classical results of Mathias about forcing extensions by Mathias reals imply that every CBER on the Ellentuck Ramsey space is hyperfinite when restricted to some pure Ellentuck cube. In this talk we show that the Milliken space M of strong trees satisfies a much stronger canonization property: if E is CBER on M then for the Milliken-generic T in M we have that E and = agree on the pure Milliken cube [T]. This is joint work with Aristotelis Panagiotopoulos.

This Week in Logic at CUNY

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

- - - - Monday, Feb 21, 2022 - - - -



- - - - Tuesday, Feb 22, 2022 - - - -



- - - - Wednesday, Feb 23, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     David Roberts.
Date and Time:     Wednesday February 23, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Do you have what it takes to use the diagonal argument?

Abstract: Lawvere's reformulation of the diagonal argument captured many instances from the literature in an elegant and abstract category-theoretic treatment. The original version used cartesian closed categories, but gave a nod to how the statement of the argument could be adjusted so as to make fewer demands on the category. In fact the argument, and the fixed-point theorem that Lawvere provided as the positive version of the argument, both require much less than Lawvere stated. This talk will give an outline of Lawvere's version of the diagonal argument, his corresponding fixed-point theorem, and then cover a few versions obtained recently that drop assumptions on the properties/structure of the category at hand.





- - - - Thursday, Feb 24, 2022 - - - -



- - - - Friday, Feb 25, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 25, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Richard Matthews, University of Leeds
Big classes and the respected model

In standard (ZFC) set theory, proper classes are not sets because they are too 'big' or, to put it in a formal way, because they surject onto any non-zero ordinal. We shall study this notion of 'bigness' in weaker systems of set theory, in particular those in which the Power Set Axiom fails. We will observe that in many such theories it is possible to have proper classes which are not big.

As part of this, we shall see a failed attempt to find a proper class which is not big in the theory ZF without Power Set but with Collection - which is by taking a certain symmetric submodel of a class forcing. It will turn out that this approach fails because, unlike in the set forcing case, the symmetric submodel of a class forcing need not exhibit many of the nice properties that we would expect. Notably, Collection may fail and, in fact, it is unclear which axioms need necessarily hold.

This will lead to the definition of the 'Respected Model', an alternative approach to defining a submodel of a class forcing in which Choice fails. We will investigate the properties of this new model and compare it to the symmetric version.





- - - - Monday, Feb 28, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 28, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Michael Burton (Yale).
Title: Paraconsistency with some detachment

Abstract: In this talk, a proof-of-concept logic is presented that is like first-order LP (the “logic of paradox”) except things behave classically within the scope of universal quantifiers. This logic’s material conditional does not, in general, detach, but much can be deduced with it. Structures for this logic are classical first-order structures equipped with a congruence relation, giving this logic a connection to Priest’s collapsing lemma for LP. Some possible improvements to this logic are then discussed. One of these involves separating classicality from universal quantification, having classicality be mediated instead by operators that interact with variable assignments. Finally, the relevance of logics of this kind to various logical paradoxes is discussed.





- - - - Tuesday, Mar 1, 2022 - - - -



- - - - Wednesday, Mar 2, 2022 - - - -



- - - - Thursday, Mar 3, 2022 - - - -



- - - - Friday, Mar 4, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 4, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Tom Benhamou, Tel Aviv University


- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

Next CMU math logic seminar

Carnegie Mellon Logic Seminar
TUESDAY, February 22, 2022 Mathematical logic seminar: 3:30 P.M., Online, Sam Sanders, Ruhr-Universitaet Bochum Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: The two-dimensional nature of ordinary mathematics ABSTRACT: The usual foundations of mathematics (ZFC set theory) are 'two-dimensional' in nature in that given a theorem T provable in ZFC, the following two questions are unavoidable: a) is T provable in ZF alone? b) If not, which fragment of the Axiom of Choice (AC) does T imply? One reason to make this distinction is that the choice functions from AC are fundamentally non-constructive in nature (even relative to ZF). We show that ordinary mathematics, when formulated in the language of third-order arithmetic, is similarly two-dimensional in nature in that the following questions are fundamental for a theorem S: c) Is S provable from (conventional) comprehension alone? d) If not, which fragment of the neighborhood function principle (NFP) does S imply? Intellectually pleasing, NFP is a fragment of AC with continuous choice functions, i.e. provable in ZF (and much weaker systems). We discuss the weakest principle falling under d), namely the uncountability of R, and how NFP gives rise to a new computational model for comparing theorems of ordinary mathematics. This is joint work with Dag Normann.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 23rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jindrich Zapletal -- Geometric set theory II This is a continuation from the previous week. I will prove a couple of basic feature of balanced extensions of the Solovay model: they add no new sets of ordinals and contain no MAD families in particular. I will also produce the first example of a consistency result: it is consistent with ZF+DC to have a Hamel basis for R over Q, but no nonprincipal ultrafilter on natural numbers. Best, David

Logic Seminar today at 16:30 hrs

NUS Logic Seminar
Hello, a short reminder that the logic seminar today starts at 16:30 hrs Singapore time, not at the full hour as usual. Regards, Frank

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 16th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jindřich Zapletal -- Geometric Set Theory I will explain basics of the method developed with Paul Larson which obtains consistency results in choiceless set theory ZF+DC using definable forcing extensions of the Solovay model. Among recent applications, if n>0 is a natural number and Gn is the graph on n-dimensional Euclidean space connecting points of rational distance, it is consistent with ZF+DC that Gn has countable chromatic number while Gn+1 does not. Best, David

Logic Seminar Wed 16 February 2022 16:30 hrs by Rupert Hoelzl

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 February 2022, 16:30 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Rupert Hoelzl, Universitaet der Bundeswehr, Muenchen Title: Universality, optimality and randomness deficiency URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: A Martin-Loef test U is universal if it captures all sequences which are not Martin-Loef random. It is optimal if for every Martin-Loef test V there is a constant c such that, for all n, V_{n+c} subseteq U_n. We study the computational differences between universal and optimal Martin-Loef tests as well as the effects of these differences on both the notions of layerwise computability and the Weihrauch degree of LAY, the function that produces a bound on the randomness deficiency of a given Martin-Loef random sequence. We prove several robustness and idempotence results concerning the Weihrauch degree of LAY and we show that layerwise computability is more restrictive than Weihrauch reducibility to LAY. Along similar lines, we also study the principle RD, a variant of LAY outputting the precise randomness deficiency of sequences instead of only an upper bound as LAY. This is joint work with Paul Shafer. The paper is available as in the Annals of Pure and Applied Logic, https://doi.org/10.1016/j.apal.2015.05.006

Logic Seminar Wed 16 February 2022 16:30 hrs by Rupert Hoelzl

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 February 2022, 16:30 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Rupert Hoelzl, Universitaet der Bundeswehr, Muenchen Title: Universality, optimality and randomness deficiency URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: A Martin-Loef test U is universal if it captures all sequences which are not Martin-Loef random. It is optimal if for every Martin-Loef test V there is a constant c such that, for all n, V_{n+c} subseteq U_n. We study the computational differences between universal and optimal Martin-Loef tests as well as the effects of these differences on both the notions of layerwise computability and the Weihrauch degree of LAY, the function that produces a bound on the randomness deficiency of a given Martin-Loef random sequence. We prove several robustness and idempotence results concerning the Weihrauch degree of LAY and we show that layerwise computability is more restrictive than Weihrauch reducibility to LAY. Along similar lines, we also study the principle RD, a variant of LAY outputting the precise randomness deficiency of sequences instead of only an upper bound as LAY. This is joint work with Paul Shafer. The paper is available as in the Annals of Pure and Applied Logic, https://doi.org/10.1016/j.apal.2015.05.006

This Week in Logic at CUNY

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

- - - - Monday, Feb 14, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 14, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Ekaterina Kubyshkina (Campinas)
Title: Ignorance as an excuse, formally

Abstract: In the current literature on epistemology there is a lively debate on which type of ignorance may provide a moral excuse. A good candidate is the one in which an agent has never considered or thought about a true proposition p. From a logical perspective, it is usual to model situations involving ignorance by means of epistemic logic. However, no formal analysis was provided for ignorance as an excuse. First, we will argue that if ignorance is expressed via standard modalities of knowledge and belief, one is unable to represent ignorance as an excuse. Secondly, we fill this gap by providing an original logical setting for modelling this type of ignorance. In particular, we introduce a complete and sound logic in which ignorance is expressed as a primitive modality. Semantically, the logic is characterized by Kripke semantics with possibly incomplete worlds. Moreover, in order to consider the conditions of a possible change of an agent’s ignorance, we will extend the setting by considering public announcements.



- - - - Tuesday, Feb 15, 2022 - - - -



- - - - Wednesday, Feb 16, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Date and Time:     Wednesday February 16, 2022, 7:00 - 8:30 PM., IN PERSON MEETING, GC Room 6417.
Speaker:     Emilio Minichiello, CUNY Graduate Center.
Title:     Category Theory ∩ Differential Geometry.

·  Abstract: In this talk we will take a tour through some areas of math at the intersection of category theory and differential geometry. We will talk about how the use of category theory works towards solving 2 problems: 1) to give rigorous definitions and techniques to study increasingly complicated objects in differential geometry that are coming from physics, like orbifolds and bundle gerbes, and 2) to find good categories in which to embed the category of finite dimensional smooth manifolds, without losing too much geometric intuition. This involves the study of Lie groupoids, sheaves, diffeological spaces, stacks, and infinity stacks. I will try to motivate the use of these mathematical objects and how they help mathematicians understand differential geometry and expand its scope.


- - - - Thursday, Feb 17, 2022 - - - -



- - - - Friday, Feb 18, 2022 - - - -


Set Theory Seminar
CUNY Graduate Center, Friday, February 18, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sittinon Jirattikansakul, Tel Aviv University
Forcing with overlapping supercompact extenders: Part II

In the paper 'Blowing up the power of a singular cardinal of uncountable cofinality', Gitik introduced the forcing which can violate the SCH at singular cardinals of any cofinalities, assuming that the singular cardinals are also singular in the ground model. The forcing is built up from a Mitchell increasing sequence of strong extenders, and it preserves all cardinals and cofinalities in the generic extension. In this talk, we will discuss a forcing which is built from a Mitchell increasing sequence of supercompact extenders. The forcing also violates the SCH at singular cardinals of any cofinalities which are singular in the ground model. An important feature of this forcing is that it is possible to collapse the successor of a singular cardinal, while preserving cardinals above it.






Next Week in Logic at CUNY:

- - - - Monday, Feb 21, 2022 - - - -



- - - - Tuesday, Feb 22, 2022 - - - -



- - - - Wednesday, Feb 23, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     David Roberts.
Date and Time:     Wednesday February 23, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Do you have what it takes to use the diagonal argument?

Abstract: Lawvere's reformulation of the diagonal argument captured many instances from the literature in an elegant and abstract category-theoretic treatment. The original version used cartesian closed categories, but gave a nod to how the statement of the argument could be adjusted so as to make fewer demands on the category. In fact the argument, and the fixed-point theorem that Lawvere provided as the positive version of the argument, both require much less than Lawvere stated. This talk will give an outline of Lawvere's version of the diagonal argument, his corresponding fixed-point theorem, and then cover a few versions obtained recently that drop assumptions on the properties/structure of the category at hand.





- - - - Thursday, Feb 24, 2022 - - - -



- - - - Friday, Feb 25, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 25, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Richard Matthews, University of Leeds




- - - - 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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Next two CMU math logic seminars

Carnegie Mellon Logic Seminar
TUESDAY, February 15, 2022 Mathematical logic seminar: 3:30 P.M., Online, Dag Normann, University of Oslo Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: The complexity of operators constructed in mainstream mathematics ABSTRACT: In an ongoing project with Sam Sanders, we have analysed third order theorems in mainstream mathematics both from the viewpoints of Kohlenbach's higher order reverse mathematics and Kleene's higher order computability theory. Based on case studies involving theorems like the Heine-Borel theorem, Lindelöf's lemma and the Jordan decomposition theorem we observe that constructions in mainstream mathematics give rise to natural functionals of type three of a kind that hitherto has remained unobserved in higher order computability theory. In this talk we will discuss both such case studies and a possible complexity/computability model useful for discussing the nature of such operators. TUESDAY, February 22, 2022 Mathematical logic seminar: 3:30 P.M., Online, Sam Sanders, Ruhr-Universitaet Bochum Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: The two-dimensional nature of ordinary mathematics ABSTRACT: The usual foundations of mathematics (ZFC set theory) are 'two-dimensional' in nature in that given a theorem T provable in ZFC, the following two questions are unavoidable: a) is T provable in ZF alone? b) If not, which fragment of the Axiom of Choice (AC) does T imply? One reason to make this distinction is that the choice functions from AC are fundamentally non-constructive in nature (even relative to ZF). We show that ordinary mathematics, when formulated in the language of third-order arithmetic, is similarly two-dimensional in nature in that the following questions are fundamental for a theorem S: c) Is S provable from (conventional) comprehension alone? d) If not, which fragment of the neighborhood function principle (NFP) does S imply? Intellectually pleasing, NFP is a fragment of AC with continuous choice functions, i.e. provable in ZF (and much weaker systems). We discuss the weakest principle falling under d), namely the uncountability of R, and how NFP gives rise to a new computational model for comparing theorems of ordinary mathematics. This is joint work with Dag Normann.

This Week in Logic at CUNY

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

- - - - Monday, Feb 7, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 7, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Guillermo Badia (Queensland)
Title: Frame Definability in Finitely-Valued Modal Logics

Abstract: In this paper we study frame definability in finitely-valued modal logics and establish two main results via suitable translations: (1) in finitely-valued modal logics one cannot define more classes of frames than are already definable in classical modal logic, and (2) a large family of finitely-valued modal logics define exactly the same classes of frames as classical modal logic (including modal logics based on finite Heyting and MV-algebras). In this way one may observe, for example, that the celebrated Goldblatt–Thomason theorem applies immediately to these logics. In particular, we obtain the central result from [B. Teheux. Modal definability for Łukasiewicz validity relations. Studia Logica 104 (2): 343–363 (2016)] with a much simpler proof and answer one of the open questions left in that paper. Moreover, the proposed translations allow us to determine the computational complexity of a big class of finitely-valued modal logics.

Note: This is joint work with Carles Noguera and Xavier Caicedo.



- - - - Tuesday, Feb 8, 2022 - - - -



- - - - Wednesday, Feb 9, 2022 - - - -



- - - - Thursday, Feb 10, 2022 - - - -



- - - - Friday, Feb 11, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 11, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sittinon Jirattikansakul, Tel Aviv University
Forcing with overlapping supercompact extenders

In the paper 'Blowing up the power of a singular cardinal of uncountable cofinality', Gitik introduced the forcing which can violate the SCH at singular cardinals of any cofinalities, assuming that the singular cardinals are also singular in the ground model. The forcing is built up from a Mitchell increasing sequence of strong extenders, and it preserves all cardinals and cofinalities in the generic extension. In this talk, we will discuss a forcing which is built from a Mitchell increasing sequence of supercompact extenders. The forcing also violates the SCH at singular cardinals of any cofinalities which are singular in the ground model. An important feature of this forcing is that it is possible to collapse the successor of a singular cardinal, while preserving cardinals above it.




Next Week in Logic at CUNY:

- - - - Monday, Feb 14, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 14, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Ekaterina Kubyshkina (Campinas)
Title: Ignorance as an excuse, formally

Abstract: In the current literature on epistemology there is a lively debate on which type of ignorance may provide a moral excuse. A good candidate is the one in which an agent has never considered or thought about a true proposition p. From a logical perspective, it is usual to model situations involving ignorance by means of epistemic logic. However, no formal analysis was provided for ignorance as an excuse. First, we will argue that if ignorance is expressed via standard modalities of knowledge and belief, one is unable to represent ignorance as an excuse. Secondly, we fill this gap by providing an original logical setting for modelling this type of ignorance. In particular, we introduce a complete and sound logic in which ignorance is expressed as a primitive modality. Semantically, the logic is characterized by Kripke semantics with possibly incomplete worlds. Moreover, in order to consider the conditions of a possible change of an agent’s ignorance, we will extend the setting by considering public announcements.



- - - - Tuesday, Feb 15, 2022 - - - -



- - - - Wednesday, Feb 16, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Date and Time:     Wednesday February 16, 2022, 7:00 - 8:30 PM., IN PERSON MEETING, GC Room 6417.
Speaker:     Emilio Minichiello, CUNY Graduate Center.
Title:     Category Theory ∩ Differential Geometry.

·  Abstract: In this talk we will take a tour through some areas of math at the intersection of category theory and differential geometry. We will talk about how the use of category theory works towards solving 2 problems: 1) to give rigorous definitions and techniques to study increasingly complicated objects in differential geometry that are coming from physics, like orbifolds and bundle gerbes, and 2) to find good categories in which to embed the category of finite dimensional smooth manifolds, without losing too much geometric intuition. This involves the study of Lie groupoids, sheaves, diffeological spaces, stacks, and infinity stacks. I will try to motivate the use of these mathematical objects and how they help mathematicians understand differential geometry and expand its scope.


- - - - Thursday, Feb 17, 2022 - - - -



- - - - Friday, Feb 18, 2022 - - - -


Set Theory Seminar
CUNY Graduate Center, Friday, February 18, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sittinon Jirattikansakul, Tel Aviv University
Forcing with overlapping supercompact extenders: Part II

In the paper 'Blowing up the power of a singular cardinal of uncountable cofinality', Gitik introduced the forcing which can violate the SCH at singular cardinals of any cofinalities, assuming that the singular cardinals are also singular in the ground model. The forcing is built up from a Mitchell increasing sequence of strong extenders, and it preserves all cardinals and cofinalities in the generic extension. In this talk, we will discuss a forcing which is built from a Mitchell increasing sequence of supercompact extenders. The forcing also violates the SCH at singular cardinals of any cofinalities which are singular in the ground model. An important feature of this forcing is that it is possible to collapse the successor of a singular cardinal, while preserving cardinals above it.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

Logic Seminar Wed 9 Feb 2022 16:00 hrs at NUS by Xie Ruofei

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 9 February 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Xie Ruofei Title: Convergence property and randomness URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Consider the sum of the series (-1)^{x_n}a_n over n, where x_n is a binary sequence and a_n is a sequence of real numbers. We say the sequence x_n has convergence property if the sum above converges for every computable sequence of real numbers whose sum \sum_n a_n^2 converges computably. Downey, Greenberg, and Tanggara showed in their unpublished paper that every Schnorr random series x_n has convergence property. In this talk, we will focus on convergence property and show its similarities and differences with randomness. This is joint work with Noam Greenberg.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 9th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino -- There may be no I-ultrafilter for any F_sigma ideal I (continued) The notion of I-ultrafilter was introduced by Baumgartner, and it has been useful in providing a framework for classifying many combinatorial properties of ultrafilters. In this talk we prove, however, that the class of F_sigma ideals may provide a vacuous classification of the combinatorial properties of ultrafilters, that is, F_sigma ideals may be not useful in providing combinatorial information about ultrafilters. This in turn implies that consistently there is no Hausdorff ultrafilter, thus answering a classical question of M. Di Nasso and M. Forti. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
Welcome back, everyone!
- Jonas

This Week in Logic at CUNY:

- - - - Monday, Jan 31, 2022 - - - -



- - - - Tuesday, Feb 1, 2022 - - - -



- - - - Wednesday, Feb 02, 2022 - - - -



- - - - Thursday, Feb 03, 2022 - - - -



- - - - Friday, Feb 04, 2022 - - - -



Next Week in Logic at CUNY:

- - - - Monday, Feb 7, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 7, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Guillermo Badia (Queensland)
Title: Frame Definability in Finitely-Valued Modal Logics

Abstract: In this paper we study frame definability in finitely-valued modal logics and establish two main results via suitable translations: (1) in finitely-valued modal logics one cannot define more classes of frames than are already definable in classical modal logic, and (2) a large family of finitely-valued modal logics define exactly the same classes of frames as classical modal logic (including modal logics based on finite Heyting and MV-algebras). In this way one may observe, for example, that the celebrated Goldblatt–Thomason theorem applies immediately to these logics. In particular, we obtain the central result from [B. Teheux. Modal definability for Łukasiewicz validity relations. Studia Logica 104 (2): 343–363 (2016)] with a much simpler proof and answer one of the open questions left in that paper. Moreover, the proposed translations allow us to determine the computational complexity of a big class of finitely-valued modal logics.

Note: This is joint work with Carles Noguera and Xavier Caicedo.



- - - - Tuesday, Feb 8, 2022 - - - -



- - - - Wednesday, Feb 9, 2022 - - - -



- - - - Thursday, Feb 10, 2022 - - - -



- - - - Friday, Feb 11, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 11, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sittinon Jirattikansakul, Tel Aviv University
Forcing with overlapping supercompact extenders

In the paper 'Blowing up the power of a singular cardinal of uncountable cofinality', Gitik introduced the forcing which can violate the SCH at singular cardinals of any cofinalities, assuming that the singular cardinals are also singular in the ground model. The forcing is built up from a Mitchell increasing sequence of strong extenders, and it preserves all cardinals and cofinalities in the generic extension. In this talk, we will discuss a forcing which is built from a Mitchell increasing sequence of supercompact extenders. The forcing also violates the SCH at singular cardinals of any cofinalities which are singular in the ground model. An important feature of this forcing is that it is possible to collapse the successor of a singular cardinal, while preserving cardinals above it.



- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

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

Logic Seminar 3 February 2022 16:00 hrs at NUS by Andre Nies

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Thursday, 3 February 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Andre Nies, The University of Auckland Title: The structure of the class of K-trivial sets URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The K-trivial sets are antirandom in the sense that the initial segment complexity in terms of prefix-free Kolmogorov complexity K grows as slowly as possible. Chaitin introduced this notion in about 1975, and showed that each K-trivial is Turing below the halting set. Shortly after, Solovay proved that a K-trivial set can be noncomputable. In the past two decades, many alternative characterisations of this class have been found: properties such as being low for K, low for Martin-Loef (ML) randomness, and a basis for ML randomness, which state in one way or the other that the set is close to computable. Initially, the class of noncomputable K-trivials appeared to be amorphous. More recently, an internal structure has been found. Most of these results can be phrased in the language of a reducibility on the K-trivials which is weaker than Turing's: A is ML-below B if each ML-random computing B also computes A. Bienvenu, Greenberg, Kucera, Nies and Turetsky (JEMS 2016) showed that there an ML complete K-trivial set. Greenberg, Miller and Nies (JML, 2019) established a dense hierarchy of subclasses of the K-trivials based on fragments of Omega computing the set, and each such subclass is an initial segment for ML. More recent results (see arxiv.org/abs/1707.00258, updated and submitted Dec 2020) generalise these approaches using cost functions. They also show that each K-trivial set is ML-equivalent to a c.e. K-trivial. The extreme lowness of K-trivials, far from being an obstacle, allows for methods which don't work in a wider setting. The talk provides an overview and discusses open questions. For instance, is ML-completeness an arithmetical property of K-trivials? This is joint work with Noam Greenberg, Joseph Miller and Dan Turetsky

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Rupert McCallum
TITLE: Intrinsic Justifications in Set theory
DATE: 2 February 2022
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Logic Seminar 26 January 2022 16:00 hrs at NUS by Zhang Jing (today)

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 26 January 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Zhang Jing Title: Ramsey-type theorems on large structures URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Structures like trees, linear orders, partial orders, graphs have been widely studied in different areas of mathematics. The Ramsey-type theorems we will discuss usually take the following form: for any given coloring of the structure, there exists a "large sub-structure" that intersects "very few" color classes. One example is a theorem of Laver that states for any finite coloring of Q x Q (ordered pairs of rationals), there exists X, Y order isomorphic to Q, such that X x Y intersects at most 2 color classes. We will discuss the uncountable analogues of these statements and their consistency. In particular, a diagonal version of the Halpern-Lauchli theorem plays a key role. The differences between countable combinatorics and uncountable combinatorics will be highlighted.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 26th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino -- There may be no I-ultrafilter for any F_sigma ideal I The notion of I-ultrafilter was introduced by Baumgartner, and it has been useful in providing a framework for classifying many combinatorial properties of ultrafilters. In this talk we prove, however, that the class of F_sigma ideals may provide a vacuous classification of the combinatorial properties of ultrafilters, that is, F_sigma ideals may be not useful in providing combinatorial information about ultrafilters. This in turn implies that consistently there is no Hausdorff ultrafilter, thus answering a classical question of M. Di Nasso and M. Forti. Best, David

(KGRC) video recording of Víctor Torres's talk

Kurt Godel Research Center
A recording of the talk of Víctor Torres from January 13th at the KGRC Logic Colloquium can be found here: https://univienna.zoom.us/rec/share/c3uO9AKcscJmC_PiuEwwdF_keDWgnGJaXjHykFSUX3pvdT5huEU0BHjw5rFdJdVc.AN_ekNznONDnOZD0 Password: !F8^vg followed by 7j

(KGRC) Logic Colloquium talk on Thursday, January 27

Kurt Godel Research Center
Logic Colloquium Kurt Gödel Research Center Thursday, January 27 "The Banach-Tarski paradox, monsters and their gentler cousins" Yash Lodha (Uni Wien) The Banach-Tarski paradox is one of the most striking and counterintuitive phenomena in all of mathematics. Von Neumann's study of the paradox led to the formulation of the so called von Neumann-Day problem, which has been attributed to Mahlon Day from the 1950s. The problem was solved in the late 70s by the construction of various finitely generated "monster" groups. However, I will explain how elementary tools from descriptive set theory recently led to the construction of considerably "less scary" new solutions, some of which are finitely presented (and even type F_{\infty}). Time and Place Talk at 3:00pm via Zoom--if you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Welcome back, and Happy New Year!  Note that CUNY's semester begins on January 28th.  However, there are some meetings taking place prior to that - see below.

Best,
Jonas

This Week in Logic at CUNY:

- - - - Monday, Jan 17, 2022 - - - -



- - - - Tuesday, Jan 18, 2022 - - - -



- - - - Wednesday, Jan 19, 2022 - - - -



- - - - Thursday, Jan 20, 2022 - - - -



- - - - Friday, Jan 21, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, January 21, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Wolfgang Wohofsky, University of Vienna
Distributivity spectrum and fresh functions: Part II

We discuss different notions of a distributivity spectrum of forcings.

In the first talk, I will mainly focus on the notion of fresh functions and the corresponding spectrum. A function with domain lambda is fresh if it is new but all its initial segments are in the ground model. I will give general facts how to compute the fresh function spectrum, also discussing what sets are realizable as a fresh function spectrum of a forcing. Moreover, I will provide several examples, including well-known tree forcings on omega such as Sacks and Mathias forcing, as well as Prikry and Namba forcing to illustrate the difference between fresh functions and fresh subsets.

In the second talk, I will also discuss another ('combinatorial') distributivity spectrum; most importantly, analyzing this notion for the forcing P(omega)/fin.

This is joint work with Vera Fischer and Marlene Koelbing.






Next Week in Logic at CUNY:

- - - - Monday, Jan 24, 2022 - - - -



- - - - Tuesday, Jan 25, 2022 - - - -



- - - - Wednesday, Jan 26, 2022 - - - -



- - - - Thursday, Jan 27, 2022 - - - -



- - - - Friday, Jan 28, 2022 - - - -



- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

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(KGRC) Set Theory Seminar talk on Tuesday, January 18

Kurt Godel Research Center
The KGRC welcomes as guest: Gunter Fuchs (host: Vera Fischer) will visit the KGRC from January 17 to January 20 and give a talk (see below). * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, January 18 "Blurry definability" Gunter Fuchs (City University of New York, USA) In this talk on ongoing research, I analyze blurry forms of ordinal definability and their hereditary versions which generalize ideas due to Hamkins/Leahy and Tzouvaras. Classically, a set is ordinal definable if it is the _unique_ object satisfying some first order property in which ordinal parameters may occur. Given a cardinal kappa, I define that a set is

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 19th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Variations on theorems of Silver and Galvin-Hajnal We will begin by reviewing the celebrated theorems of Silver and Galvin-Hajnal about cardinal exponentiation at singular cardinals of uncountable cofinality. We will then present some recent variations on these theorems concerning cardinal characteristics at singular cardinals, focusing in particular on the dominating number. Also, there is a small online set theory conference tomorrow (Friday), see https://www1.maths.leeds.ac.uk/~pmtadb/STUK7/STUK7.html Best, David

Logic Seminar Talk 19 Jan 2022 16:00 hrs at NUS over Zoom by Ye Jinhe

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 19 January 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Ye Jinhe, Institut de Mathematiques de Jussieu - Paris Rive Gauche Title: Curve-Excluding Fields Abstract: Consider the class of fields with Char(K)=0 and x^4+y^4=1 has only 4 solutions in K, we show that this class has a model companion, which we denote by curve-excluding fields. Curve-excluding fields provides (counter)examples to various questions. Model theoretically, they are model complete. Field theoretically, they are not large and unbounded. Time permitting, we will discuss other aspects such as decidability of such fields. Joint work with Will Johnson and Erik Walsberg. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

World Logic Day Event // January 14

Set Theory Seminar at the Fields Institute
January 14th is World Logic Day, as designated by the UNSECO, see On this day the Toronto Set Theory Seminar at the Fields Institute will hold a special session with 5 short talks (20 minutes each), showcasing recent research by faculty and postdocs at University of Toronto: ==================================================================== Friday January 14 at the Set Theory Seminar (Fields Institute, Toronto): Location: https://zoom.us/j/92701726800 ==================================================================== 13:30 Ivan Ongay-Valverde and Franklin D. Tall﹡: A New Topological Generalization of Descriptive Set Theory We generalize the K-analytic spaces to the K-σ-projective spaces. We get an application to Selection Principles: Theorem. The Axiom of σ-Projective Determinacy implies every K-σ-projective Menger space is Hurewicz. -------------------------------------------------------------------- 13:50 Ivan Ongay Valverde﹡ and Franklin D. Tall: Upper semi-continuous compact-valued functions and the K-sigma-projective hierarchy Completing the previous talk, we introduce USCCV functions (actually, multifunctions), which were employed in the study of K-analytic spaces, and show how to use them to prove the crucial: Theorem. K-σ-projective spaces are projectively σ-projective. -------------------------------------------------------------------- 14:10 Christopher J. Eagle, Clovis Hamel﹡, Sandra Müller, and Franklin D. Tall: An undecidable extension of Morley's theorem on the number of countable models Morley’s theorem states that the number of non-isomorphic countable models of a complete countable first-order theory in a countable language is ℵ0 or ℵ1 or 2ℵ0. Vaught’s conjecture remains one of the most important open problems in Model Theory, asking whether ℵ1 can be omitted in the conclusion of Morley’s theorem. Even though Vaught’s conjecture is trivially false in second-order logic, no result was known regarding Morley’s trichotomy for second-order logic. We shall show using forcing, large cardinals and descriptive set theory that the second-order version of Morley’s theorem is undecidable. -------------------------------------------------------------------- 14:30 Andrew Marks and Spencer Unger﹡: Flows on the torus In joint work with Andrew Marks, we gave a constructive solution to Tarski's circle squaring problem. In particular, we showed that a disk and a square with the same area are equidecomposible using translations. One important innovation of the proof was to construct a real valued flow from the disk to the square. The notion of flow that we use comes from the study of networks and is related to max flow-min cut. In this talk, I will sketch a simpler construction of a real-valued flow from the disk to the square, which is joint work with Andrew Marks. Using discrepancy estimates due to Laczkovich, this argument works for sets whose boundary has small upper Minkowski dimension. I will also mention ongoing work with Anton Bernshteyn and Anush Tserunyan where we construct a large and diverse collection of flows under the same assumptions. -------------------------------------------------------------------- 14:50 Haosui Duanmu, David Schrittesser﹡, and William Weiss: Infinitesimals and Probabilities In joint work with Haosui Duanmu and William Weiss, we investigate applications of nonstandard analysis in measure theory. The use of infinitesimals and hyperfinite probability spaces offers alternative viewpoints on many classical problems, via Peter Loeb's construction of measures using hyperfinite probability mass functions to construct classical measures. In this talk, I will describe a solution to a problem posed by Keisler, about Loeb measures, and also mention applications in statistics which are joint work with Haosui Duanmu and Daniel Roy. -------------------------------------------------------------------- Find this program also at: For more information about events worldwide see also -- http://homepage.univie.ac.at/david.schrittesser pronouns he/him

(KGRC) (corrected) World Logic Day 2022

Kurt Godel Research Center
(Correction: Parts of the most recent announcement gave the wrong begin time for Victor's talk in the Logic Colloquium. The correct time is 11:30am - apologies for any confusion caused! Below is the corrected text for the announcement.) On January 14th is the World Logic Day. The KGRC is making a small contribution towards the celebrations by dedicating the Tuesday and Thursday seminars next week to it. For more information about events worldwide see https://wld.cipsh.international/background.html * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, January 11 The Set Theory Research Seminar will host five short talks given by masters and doctoral students on topics from their theses. For information regarding the schedule, titles and abstracts see the attached file (the talks are mainly intended for a student audience). Time and Place Talks at 3:00pm via Zoom - see attached file for schedule. If interested contact vera.scher@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, January 13 "Worlds without Martin's Axiom" Víctor Torres-Pérez (TU Wien) The first of Hilbert's famous list of problems at the beginning of the 20th century was to establish Cantor's Continuum Hypothesis (CH), i.e. if there is no uncountable subset of the reals with cardinality strictly less than the continuum. After the works of Gödel and Cohen, it was concluded that the traditional axioms of Set Theory (ZFC) cannot decide CH. Since then, new axioms have emerged. Prominently we have Forcing Axioms. One of the first Forcing Axioms ever considered was Martin's Axiom (MA). While MA implies the negation of the CH, it does not decide the exact value of the continuum. However, generalizations of MA like the Proper Forcing Axiom (PFA) or Martin's Maximum (MM) do imply that the continuum is the second uncountable cardinal. Besides, PFA or MM imply the negation of certain square principles or tree properties (among a very large number of interesting consequences). This means in particular that these axioms require the existence of large cardinals. There are other relatively new principles, which have strong consequences similar to the ones from PFA or MM, but they can coexist consistently with the absence of MA or even imply this absence. A couple of these principles are, for example, Rado's Conjecture (RC) and the P-Ideal Dichotomy (PID). We will give a general review of results involving these kinds of principles, including some of ours obtained along the previous years. There, it is possible to observe that even if they can avoid MA, they are still quite powerful like these traditional Forcing Axioms. We will expose one of our last results, where we prove (with L. Wu) that PID implies the negation of a certain type of two-cardinals square principle. Time and Place Talk at 11:30am via Zoom - Please note the unusual time! If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!
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Logic Day Special Wed 12 Jan 2022 16:00 hrs SGT

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 12 Jan 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 (1) Logic Day Special For the logic day, everyone is encouraged to present his or her favourate result, which is not required to be recent. Alternatively the participant can also present open questions, perhaps with partial results. Every contribution is welcome. For planning purposes, please email contributions to Frank Stephan (fstephan@comp.nus.edu.sg) and Yang Yue (matyangy@nus.edu.sg). (2) Planning of Logic Seminar At http://www.comp.nus.edu.sg/~fstephan/logicseminar.html you find a schedule of the so far reserved slots. If you are willing to present a talk in the logic seminar (40 - 50 minutes), please select one day which is still free and we will note you down. The timing can be changed if needed. Also if you happen to know of someone who might be interested in giving a talk, please inform us and we will follow up with this person. Frank Stephan (fstephan@comp.nus.edu.sg) Yang Yue (matyangy@nus.edu.sg) Organisers of the Logic Seminar URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar
Dear all, No seminar tomorrow, Wednesday January 5th. The seminar meets again on Wednesday January 12th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Uhrik -- Cohen reals and partition relations Abstract: The effect of adding Cohen reals on partition relations will be discussed. Specifically, we will prove that the relation omega_2 --> (omega_2, omega:omega)^2 holds after adding Cohen reals to a model of CH. We will also prove that this result is in a sense best possible. Best, David

21.12.2021 Seminar canceled

IMPAN Working Group in Applications of Set Theory
Due to health issues of several participants we need to cancel the meeting of the seminar tomorrow 21.12.2021, when Damian Sobota was supposed to speak. We are very sorry. The talk will be postponed for March/April 2022. Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/ ----- Em 18 de Dez de 2021, em 13:35, Piotr Koszmider piotr.koszmider@impan.pl escreveu: | Seminar: Working group in applications of set theory, IMPAN | | Tuesday, 21.12.2021, 13.30, room 403 | | Speaker: Damian Sobota (KGRC, Vienna) | | Title: "Measures with the Additive Property and the random forcing" | | Abstact: "Let μ be a finitely additive probability measure on ω which vanishes | on points, that is, μ({n})=0 for every n∈ω. It follows immediately that μ is | not σ-additive, however it may be almost σ-additive in the following weak | sense. We say that μ has the Additive Property, (AP) in short, if for every | sequence (An) of pairwise disjoint subsets of ω there is a subset A such that | A_n\A is finite for every n∈ω and μ(A)=Σn μ(A_n). Equivalently, for every | decreasing sequence (A_n) of subsets of ω there is a subset A such that A\A_n | is finite for every n∈ω and μ(A)=limn μ(A_n). The latter definition implies | immediately that, e.g., an ultrafilter U on ω is a P-point if and only if the | one-point measure δ_U has (AP). And similarly as in the case of P-points the | existence of measures with (AP) is independent of ZFC. | | During my talk I will discuss basic properties of (families of) measures with | (AP) as well as show, at least briefly, that using old ideas of Solovay and | Kunen one can obtain a non-atomic measure with (AP) in the random model. The | latter result implies that in this model there exists a ccc P-set in ω*, which | may be treated as a (weak) partial answer to the question asking whether there | are P-points in the random model. | | This is a joint work with Piotr Borodulin-Nadzieja." | | |

Damian Sobota, Measures with the Additive Property and the random forcing

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 21.12.2021, 13.30, room 403 Speaker: Damian Sobota (KGRC, Vienna) Title: "Measures with the Additive Property and the random forcing" Abstact: "Let μ be a finitely additive probability measure on ω which vanishes on points, that is, μ({n})=0 for every n∈ω. It follows immediately that μ is not σ-additive, however it may be almost σ-additive in the following weak sense. We say that μ has the Additive Property, (AP) in short, if for every sequence (An) of pairwise disjoint subsets of ω there is a subset A such that A_n\A is finite for every n∈ω and μ(A)=Σn μ(A_n). Equivalently, for every decreasing sequence (A_n) of subsets of ω there is a subset A such that A\A_n is finite for every n∈ω and μ(A)=limn μ(A_n). The latter definition implies immediately that, e.g., an ultrafilter U on ω is a P-point if and only if the one-point measure δ_U has (AP). And similarly as in the case of P-points the existence of measures with (AP) is independent of ZFC. During my talk I will discuss basic properties of (families of) measures with (AP) as well as show, at least briefly, that using old ideas of Solovay and Kunen one can obtain a non-atomic measure with (AP) in the random model. The latter result implies that in this model there exists a ccc P-set in ω*, which may be treated as a (weak) partial answer to the question asking whether there are P-points in the random model. This is a joint work with Piotr Borodulin-Nadzieja." Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 22nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. We will have Jan Grebik as a guest (speaker). Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

This will be the final mailing of This Week In Logic for the semester - we will resume in early January.  Happy Holidays to all!

Jonas


This Week in Logic at CUNY:

- - - - Monday, Dec 13, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, December 13, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Cezary Cieśliński, University of Warsaw
On the principle of disjunctive correctness

The disjunctive correctness principle (DC) states that a disjunction of arbitrary (possibly nonstandard) length is true if and only if one of its disjuncts is true. On first sight, the principle seems an innocent and natural generalization of the familiar compositional truth axiom for disjunction. However, Ali Enayat and Fedor Pakhomov demonstrated that (DC) has the same strength as Delta_0 induction, hence it produces a non-conservative extension of the background arithmetical theory.

In the presentation the proof of a stronger result will be presented. Let (DC-Elim) be just one direction of (DC), namely, the implication 'if a disjunction is true, then one of it disjuncts is true'. We will show that already (DC-Elim) carries the full strength of Delta_0 induction; moreover, the proof of this fact will be significantly simpler than the original argument of Enayat and Pakhomov.




Logic and Metaphysics Workshop
Date: Monday, December 13th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Dolf Rami (Bochum)
Title: Singular existentials and three different kinds of negation

Abstract: In this paper, I will argue for a new semantic analysis of (i) singular existential and (ii) atomic sentences to be able to cover three possible types of negation of them. Firstly, I will show that all three negations of sentences of kind (i) are equivalent if we make use of referring or non-referring names, while on the other hand the three negations of sentences of kind (ii) have several non-equivalent readings if non- referring names are used. Secondly, I will review the partial solutions to our problem given by Russell, Quine and Sainsbury and show in how far they fail. Thirdly, I will propose an alternative solution based on a semantics outlined in Rami (2020). Finally, I will show that we must distinguish two types of negation and that a unification in both directions fails.




- - - - Tuesday, Dec 14, 2021 - - - -

Computational Logic seminar
Tuesday December 14, 2021, 2-4pm, Eastern Time US
Contact sartemov@gc.cuny.edu for a zoom link
Speaker: V. Alexis Peluce, CUNY Graduate Center
Title: Explicit Modal Logic as the Structure of Relevance

Abstract. Orlov and Gödel pioneered the method of syntactic translation of propositional formulas into modal language. Justification Logic takes this a step further by revealing the explicit content of individual modalities. Sergei Artemov extended Gödel's work by showing that S4 can be interpreted in the Logic of Proofs, which can in turn be interpreted in terms of arithmetical proof predicates, thereby providing a rigorous arithmetical foundation for constructivism.

In this work, we examine Classical Logic through the Gödel-Artemov lens. The paradoxes of material implication are a family of classical implications that diverge in meaning from the natural language conditional. We present seven such paradoxes, translate them into S5|the natural modal counterpart of CPC|and then populate the resulting S5 formulas with explicit modalities. We show that for each of our paradoxes, there is a corresponding explicit, non-paradoxical formula. This, we suggest, provides a general method for solving the paradoxes of material implication.




- - - - Wednesday, Dec 15, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Samantha Jarvis, The CUNY Graduate Center.
Date and Time:     Wednesday December 15, 2021, 7:00 - 8:30 PM., on Zoom (contact noson@sci.brooklyn.cuny.edu for the link)
TBA


- - - - Thursday, Dec 16, 2021 - - - -



- - - - Friday, Dec 17, 2021 - - - -



Next Week in Logic at CUNY:

- - - - Monday, Dec 20, 2021 - - - -



- - - - Tuesday, Dec 21, 2021 - - - -



- - - - Wednesday, Dec 22, 2021 - - - -



- - - - Thursday, Dec 23, 2021 - - - -



- - - - Friday, Dec 24, 2021 - - - -


- - - - 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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Agnieszka Widz, Magic Sets

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 14.12.2021, 13.30, room 403 Speaker: Agnieszka Widz (Lodz University of Technology) Title: Magic Sets Abstact: Given a family of real functions F we say that a set M ⊆ ℝ is magic for F if for all f, g ∈ F we have f [M ] ⊆ g[M ] ⇒ f = g. This notion was introduced by Diamond, Pomerance and Rubel in 1981 [1]. Recently some results about magic sets were proved by Halbeisen, Lischka and Schumacher [2]. Inspired by their work I constructed two families of magic sets one of them being almost disjoint and the other one being independent. During my talk I will sketch the background and present the proof for the independent family, which uses a Kurepa tree. References: [1] H. G. Diamond, C. Pomerance, L. Rubel, Sets on which an entire function is determined by its range, Mathematische Zeitschrift, 176 (1981), 383-398. [2] L. Halbeisen, M. Lischka, S. Schumacher, Magic Sets, Real Anal. Exchange, 43 (2018), 187-204. Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Luca Motto-Ros (Torino)
TITLE: Generalized Polish spaces at reguulart uncountable cardinals
DATE: 15 December 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 15th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program; we will have another attempt at: Adam Bartoš -- KPT correspondence in the context of weak Fraïssé categories (continued) Last time we formulated the KPT correspondence theorem in our setting, and summarized abstract Fraïssé theory in our setting. Next time we discuss the weak amalgamation property, the (weak) Ramsey property in the abstract setting, recall extreme amenability, and prove the main theorem. If time permits, we mention applications for strong trees. Best, David

(KGRC) four talks on Tuesday, December 14 and one talk on Thursday, December 16

Kurt Godel Research Center
Note: Effective December 14, the password for the Set Theory Research Seminar changes (again); if you have not received the meeting link(s) by the day before the talk, please contact richard.springer@univie.ac.at! * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, December 14 The Set Theory Research Seminar on December 14th, 2021 will feature four talks given by doctoral students. Julia Millhouse and Lukas Schembecker will give 25 minute expository talks on selected topics. Marlene Koelbing and Yuxin Zhou, who are graduating doctoral students at University of Vienna and University of Florida, respectively, will give 50 minute presentations on results from their dissertations. For the schedule of the talks, titles and abstracts, please see the attached file. The Zoom link and Meeting ID will stay the same, but the password will change. If there are any questions, please direct them to vera.fischer@univie.ac.at! * * * Logic Colloquium Kurt Gödel Research Center Thursday, December 16 "Classification of definable quotients" Martin Hils (Universität Münster, Germany) In many areas of mathematics, quotient objects play an important role, and it is often useful to close a category under quotients. In the talk, we will discuss so-called imaginaries, i.e., definable quotients in first order logic. In algebraically closed and in real closed fields, imaginaries may be eliminated. In valued fields, the situation is more interesting, as there are definable quotients like the residue field and value group which may not be eliminated. In algebraically closed valued fields, the imaginaries were classified by Haskell-Hrushovski-Macpherson. We will discuss a recent generalization of their work to more general henselian valued fields, which is joint with Silvain Rideau-Kikuchi. Time and Place Talk at 3:00pm via Zoom - if you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!
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Mirna Dzamonja @ Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Title: Morass-generic structures Speaker: Mirna Dzamonja, IRIF (CNRS-Université deParis) Date and Time: Friday, December 10, 2021 - 13:30 to 15:00 (Toronto time) Abstract: We discuss a joint work with Wiesław Kubiś on a specific way of constructing structures of size ℵ1 using finite approximations, namely by organising the approximations along a simplified morass. We demonstrate a connection with Fraïssé limits and show that the naturally obtained structure of size ℵ1 is homogeneous. Moreover, this is preserved under expansions, which leads us to a partial answer to a question of Bassi and Zucker. We give some examples of interesting structures constructed, such as the antimetric space of size ℵ1. Finally, we comment on the situation when one Cohen real is added. Location: https://zoom.us/j/92701726800 ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

This Week in Logic at CUNY

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

- - - - Monday, Dec 6, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, December 6, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Bartosz Wcisło, Polish Academy of Sciences
Model theoretic characterizations of truth: Part II

This is joint work (still in progress) with Mateusz Łełyk (who gave the first part of the talk). By an axiomatic theory of truth (for the language of arithmetic, ) we mean a theory in L enriched with a fresh unary predicate  which (extends the elementary arithmetic EA and) proves all sentences of the form ( being a sentence in L) 

The collection of all sentence of the above form is normally called . It is well known that axiomatic theories of truth have a number of interesting model-theoretic consequences. For example, already relatively weak theories of truth impose recursive saturation, in the sense that the L-reduct of any model of such theory is recursively saturated. To give another example, already  imposes elementary equivalence of models, in the sense that whenever , and  (the first model is a submodel of the second one), then actually  and  are elementarily equivalent. During (both parts) of the talk we investigate which of these properties actually characterize the respective truth theory up to definability. In particular, in the first part of the talk, we prove the following results (we restrict ourselves to theories in a finite language and extending EA):

  1. Every theory which imposes elementary equivalence defines .
  2. Every theory which imposes full elementarity defines .

Additionally, we take a look at the definability relations between axiomatic truth theories and axiomatic theories of definability or skolem functions.







Logic and Metaphysics Workshop
Date: Monday, December 6th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Diderik Batens (Ghent)
Title: Every Logic has its Proper Semantics

Abstract: Many logics are sound and complete with respect to a multiplicity of semantic systems. These assign different sets of models to the logic. It will be shown that a series of problems result if all these semantic systems are on a par. I shall present a method to define a unique ‘proper’ semantics for the members of a huge class of logics, containing all usual deductive logics, and argue (i) that the proper semantics is defined in terms of syntactic criteria and so depends fully on the logic, (ii) that there are philosophical arguments to consider a logic’s proper semantics as natural, for example it correctly describes the ‘situations’ that are possible according to the logic. This solves the problems mentioned previously. Implications for the discussion on inferentialism are obvious. For some logics, the proper semantics coincides with the Henkin semantics. For other logics L, the proper semantics counts more models than the Henkin semantics: moreover, not all Henkin models are maximally L-non-trivial. A small change to the Henkin method has the effect that, for every logic L, the Henkin semantics coincides with the proper semantics.




- - - - Tuesday, Dec 7, 2021 - - - -



- - - - Wednesday, Dec 8, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Jens Hemelaer, University of Antwerp.
Date and Time:     Wednesday December 8, 2021, 7:00 - 8:30 PM., on Zoom (contact noson@sci.brooklyn.cuny.edu for the link)
Title:     Toposes of presheaves on a monoid and their points.

Abstract: In 2014, Connes and Consani constructed their Arithmetic Site, with as underlying topos the topos of presheaves on the monoid of nonzero natural numbers under multiplication. One of their surprising results is that the points of this topos are classified by a double quotient of the finite adeles, leading immediately to a link with number theory. Inspired by this, we will consider toposes of presheaves on various monoids, and discuss strategies of calculating their points. The most recent strategies (involving for example étale geometric morphisms and complete spreads) are based on joint work with Morgan Rogers.



- - - - Thursday, Dec 9, 2021 - - - -



- - - - Friday, Dec 10, 2021 - - - -

Seminar in Philosophy, Logic and Game
Friday, December 10, 10:30 AM
A Zoom link will be sent out on December 8 and will also be posted on
https://philog.arthurpaulpedersen.org/ 
Speaker: David Ellerman, University of Ljubljana
"What is Information and How to Measure it?"

Abstract: In view of the duality between subsets and quotient sets (= partitions = equivalence relations), the Boolean logic of subsets (usually presented as "propositional" logic) has a dual logic of partitions. The quantitative version of Boolean logic is the Boole-Laplace notion of logical probability. Gian-Carlo Rota held that probability is to subsets as information is to partitions, so the quantitative version of partition logic is the theory of logical entropy. This talk is an introduction to logical entropy as the natural measure (in the sense of measure theory) of information as distinctions. It is also shown that the Shannon entropy (which is not a measure) is a uniform transform of logical entropy that is a different quantification of the same notion of information as distinctions.





Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, December 10, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Eyal Kaplan, Tel Aviv University
Non-stationary support iterations of Prikry forcings and restrictions of ultrapower embeddings to the ground model, part II

Assume that  is a forcing notion,  is a generic set for it over the ground model , and a cardinal  is measurable in the generic extension. Let  be an ultrapower embedding, taken in  with a normal measure on . We consider the following questions:

1. Is the restriction of  to  an iterated ultrapower of  (by its measures or extenders)?

2. Is the restriction of  to  definable in ?

By a work of Schindler [1], the answer to the first question is affirmative, assuming that there is no inner model with a Woodin Cardinal and  is the core model. By a work of Hamkins [2], the answer to the second question is positive for forcing notions which admit a Gap below .

We will address the above questions in the context of nonstationary-support iteration of Prikry forcings below a measurable cardinal . Assuming GCH only in the ground model, we provide a positive answer for the first question, and describe in detail the structure of  restricted to  as an iteration of . The answer to the second question may go either way, depending on the choice of the measures used in the Prikry forcings along the iteration; we will provide a simple sufficient condition for the positive answer. This is a joint work with Moti Gitik.

[1] Ralf Schindler. Iterates of the core model. Journal of Symbolic Logic, pages 241–251, 2006.

[2] Joel David Hamkins. Gap forcing. Israel Journal of Mathematics, 125(1):237–252, 2001.




Next Week in Logic at CUNY:

- - - - Monday, Dec 13, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, December 6, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Cezary Cieśliński, University of Warsaw
On the principle of disjunctive correctness

The disjunctive correctness principle (DC) states that a disjunction of arbitrary (possibly nonstandard) length is true if and only if one of its disjuncts is true. On first sight, the principle seems an innocent and natural generalization of the familiar compositional truth axiom for disjunction. However, Ali Enayat and Fedor Pakhomov demonstrated that (DC) has the same strength as Delta_0 induction, hence it produces a non-conservative extension of the background arithmetical theory.

In the presentation the proof of a stronger result will be presented. Let (DC-Elim) be just one direction of (DC), namely, the implication 'if a disjunction is true, then one of it disjuncts is true'. We will show that already (DC-Elim) carries the full strength of Delta_0 induction; moreover, the proof of this fact will be significantly simpler than the original argument of Enayat and Pakhomov.




Logic and Metaphysics Workshop
Date: Monday, December 13th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Dolf Rami (Bochum)
Title: Singular existentials and three different kinds of negation

Abstract: In this paper, I will argue for a new semantic analysis of (i) singular existential and (ii) atomic sentences to be able to cover three possible types of negation of them. Firstly, I will show that all three negations of sentences of kind (i) are equivalent if we make use of referring or non-referring names, while on the other hand the three negations of sentences of kind (ii) have several non-equivalent readings if non- referring names are used. Secondly, I will review the partial solutions to our problem given by Russell, Quine and Sainsbury and show in how far they fail. Thirdly, I will propose an alternative solution based on a semantics outlined in Rami (2020). Finally, I will show that we must distinguish two types of negation and that a unification in both directions fails.




- - - - Tuesday, Dec 14, 2021 - - - -



- - - - Wednesday, Dec 15, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Samantha Jarvis, The CUNY Graduate Center.
Date and Time:     Wednesday December 15, 2021, 7:00 - 8:30 PM., on Zoom (contact noson@sci.brooklyn.cuny.edu for the link)
TBA


- - - - Thursday, Dec 16, 2021 - - - -



- - - - Friday, Dec 17, 2021 - - - -





- - - - 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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Kacper Kucharski, Overcomplete sets in selected nonseparable Banach spaces

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 7.12.2021, 13.30, room 403 Speaker: Kacper Kucharski (UW) Title: "Overcomplete sets in selected nonseparable Banach spaces" Abstact: "A subset Y of a Banach space X is called overcomplete if |Y|=dens(X) and for any set Z⊆Y, such that |Z|=|Y|, Z is linearly dense in X. A classical result says that every separable Banach space admits an overcomplete set. The main goal of the talk is to show how, using a certain Aronszajn tree, one can step-up this property for selected nonseparable Banach spaces. If there is enough time, one consistency result will also be stated and proved". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Philipp Schlicht (Bristol)
TITLE: Forcing axioms via ground model interpretations
DATE: 8 December 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Wednesday seminar

Prague Set Theory Seminar
Dear all, Because of an increasing number of covid infections among regular seminar participants, the seminar next week, Wednesday December 8th is cancelled. It is unclear whether the seminar will resume in December, no announcement = no seminar. The expected program for the next seminar is Adam Bartoš finishing his talk on KPT correspondence in the context of weak Fraïssé categories. (This week we had a talk by Chris Lambie-Hanson instead.) Moreover, there are some sad news from Kosice, see attachment. Best, David

(KGRC) Set Theory Research Seminar talk on Tuesday, December 7

Kurt Godel Research Center
Note: The KGRC Set Theory Seminar recently moved to another Zoom meeting (while other KGRC events kept their Zoom meetings). If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, December 7 "On regular countably compact R-rigid spaces" Serhii Bardyla (KGRC) A regular separable first-countable countably compact space is called a Nyikos space. A space $X$ is called R-rigid if any continuous real-valued function on $X$ is constant. Under MA we construct an R-rigid Nyikos space. This way we answer a few questions of Tzannes and extend results of Ciesielski and Wojciechowski. This is a joint work with Zdomskyy. Time and Place Talk at 3:00pm via Zoom - see top of this message

Mariam Beriashvili @ Toronto Set Theory Seminar // UNUSUAL TIME

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Title: On two-point sets and other nontrivial point sets Speaker: Mariam Beriashvili, I. Vekua Institute of Applied Mathematics, Iv. Javakhishvili Tbilisi State University, Tbilisi, Georgia Date and Time: Friday, December 3, 2021 - 10:00am to 11:30am Abstract: We consider certain pathological point sets from the general measure theoretical point of view. Namely, we discuss Mazurkiewicz sets, also called two-point sets, which have difficult and interesting descriptive as well as measure theoretic properties. Moreover, we will discuss also uniform subsets of the Euclidean space and their connections to the Mazurkiewizc sets. Also, in the talk will be considered Bernstein sets and Hamel bases. Location: https://zoom.us/j/92701726800 ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Mariam Beriashvili @ Toronto Set Theory Seminar // UNUSUAL TIME

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Title: On two-point sets and other nontrivial point sets Speaker: Mariam Beriashvili, I. Vekua Institute of Applied Mathematics, Iv. Javakhishvili Tbilisi State University, Tbilisi, Georgia Date and Time: Friday, December 3, 2021 - 10:00am to 11:30am Abstract: We consider certain pathological point sets from the general measure theoretical point of view. Namely, we discuss Mazurkiewicz sets, also called two-point sets, which have difficult and interesting descriptive as well as measure theoretic properties. Moreover, we will discuss also uniform subsets of the Euclidean space and their connections to the Mazurkiewizc sets. Also, in the talk will be considered Bernstein sets and Hamel bases. Location: https://zoom.us/j/92701726800 ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Menachem Magidor (Jerusalem)
TITLE: Borel canonization of analytic and universally Baire relations
DATE: 1 December 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Piotr Koszmider, Bidiscrete system in compact spaces

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 30.11.2021, 13.30, room 403 Speaker: Piotr Koszmider (IM PAN) Title: "Bidiscrete system in compact spaces" Abstact: "A set X of the square of a compact Hausdorff space K is called bidiscrete if for every (x, y) in X there is a continuous real valued function f on K such that f(x)=1, f(y)=0 and f(x')=f(y') for any (x', y') in X-{(x, y)}. Bidiscrete sets play role in investigations related to biorthogonal systems in Banach spaces and irredundant sets in many algebraic structures induced by the compact K, but the question if there is in ZFC a nonmetrizable compact K with no uncountable bidiscrete set remains open. There are such examples under special set-theoretic assumptions (Kunen) and there are no such totally disconnected examples under other assumptions (Todorcevic). We will discuss these and other know results and open problems.". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) seminar talks on Tuesday, November 30 and Thursday, December 2

Kurt Godel Research Center
Note: Starting November 30, the Zoom meeting ID and passcode change for the Set Theory Seminar (but remain unchanged for other KGRC seminars). If you have not received the meeting link(s) by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, November 30 "Big Ramsey degrees of 3-uniform hypergraphs are finite, part 2" David Chodounský (TU Wien) This is a continuation of the KGRC Set Theory seminar talk I gave in June 2021. I will quickly repeat the content of the first talk and focus on things I did not cover then. It is well known that the (universal countable) Rado graph has finite big Ramsey degrees. I.e., given a finite colouring of n-tuples of its vertices there is a copy of the Rado graph such that its n-tuples have at most D(n)-many colours. The proof of this fact uses a theorem of Milliken for trees. I will talk about the extension of this argument which works also for universal structures with higher arities, in particular 3-uniform hypergraphs. Joint work with M. Balko, J. Hubička, M. Konečný, and L. Vena, see https://arxiv.org/abs/2008.00268 Time and Place Talk at 3:00pm via Zoom - see top of this message * * * Logic Colloquium Kurt Gödel Research Center Thursday, December 2 "The world between aleph1 and continuum: from Martin's Axiom to Cichoń's Maximum" Martin Goldstern (TU Wien) Georg Cantor's "Continuum Hypothesis" (CH) postulates that the continuum (the cardinality of the set of real numbers) is equal to aleph1, the smallest uncountable cardinal. Martin's Axiom (MA) is a weakening of CH; it implies that all infinite cardinals below the continuum are similar to aleph0, the cardinality of a countable set. For example, MA implies that not only every countable union of null (measure zero) sets is still null, but even every union of fewer than continuum many such sets. This motivates the definition of a so-called cardinal characteristic, the additivity number of the measure zero sets - the answer to the question "how many null sets do we have to join together to get a non-null set". There is a whole zoo of such cardinal characteristics (some of them defined long before the advent of forcing); whenever you know that any countable set of objects with property X will never have property Y, you may ask how many such objects you need to get to Y. Accepting CH or just MA as an axiom gives a picture that is on the one hand very clean, but on the other hand also rather poor: most cardinal characteristics can then be shown to be equal to the continuum. In my talk I will discuss - or at least hint at - some recent (and some old) techniques for constructing "anti-MA" universes, where many cardinals between omega1 and the continuum appear as cardinal characteristics (defined by some natural properties X and Y). I will try to hide all technical details, so that my talk will hopefully be understandable also for non-set-theorists. Time and Place Talk at 3:00pm via Zoom - see top of this message

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 1st at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Adam Bartoš will continue his talk from this week. KPT correspondence in the context of weak Fraïssé categories (continued) Last time we formulated the KPT correspondence theorem in our setting, and summarized abstract Fraïssé theory in our setting. Next time we discuss the weak amalgamation property, the (weak) Ramsey property in the abstract setting, recall extreme amenability, and prove the main theorem. If time permits, we mention applications for strong trees. Best, David

Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Speaker: David Aspero, University of East Anglia Date and Time: Friday, November 26, 2021 - 1:30pm to 2:30pm Location: https://zoom.us/j/92701726800 Abstract: I aim to present the proof that the ℙmax axiom (*) is implied by Martin's Maximum++, as well as some further work related to this result and its proof. ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Chris Scambler (New York University)
TITLE: Axiomatic Potentialism
DATE: 24 November 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Kamil Ryduchowski; A Banach space admitting few operators

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 23.11.2021, 13.30, room 403, (CHANGE OF THE ROOM!) Speaker: Kamil Ryduchowski (MIM UW) Title: "A Banach space admitting few operators" Abstact: "Using the colouring discussed in our previous talk we will construct a Banach space admitting few operators in the following sense: it will be a non-separable Banach space X such that every operator on X is of the form sI + S, where s is a scalar, S is an operator with a separable range and I stands for the identity on X, i.e. every operator on X is a homothety modulo the ideal of operators with separable range. The construction is due to Shelah and Steprans". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) Set Theory Research Seminar talk on Tuesday, November 23

Kurt Godel Research Center
Set Theory Research Seminar Kurt Gödel Research Center Tuesday, November 23 "Specializing Triples and Weak Embeddability" Rahman Mohammadpour (TU Wien) A weak embedding between trees is a function that preserves the strict order. A class U of trees is said to be universal for a class C of trees if every tree in C weakly embeds in an element of U. It turns out that the pre-ordered structure induced by weak embeddability on a class C of trees is a plausible tool for the study of the elements of C. One can ask e.g., what is the universality number of a class of trees (the size of the smallest subclass which is universal)? can it be 1? whether a subclass is cofinal? etc. If CH holds, then the class of \aleph_1-wide Aronszan trees (trees of height and size \aleph_1 without cofinal branches) does not have a maximal tree under weak embeddability (this follows from Kurepa's works). Todorcevic has proved, among other things, that under MA_{\aleph_1}, the class of Aronszajn trees has no maximal object. In their joint work on wide Aronszajn trees under MA_{\aleph_1}, Dzamonja and Shelah introduced the notion of a specializing triple that connects weak embeddings to the specialization of trees. In particular, they reproved Todorcevic's result using specializing triples. In this talk, we shall focus on a variant of this notion in a general setting and demonstrate the main aspects of it. We shall then discuss some negative results on the universality problem for Aronszajn trees whose height is the successor of a regular cardinal, and hopefully, we shall finish the talk with some open problems. The results have been obtained in a collaboration with Mirna Dzamonja. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 8 1st floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the lectures we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) COVID rules may be accentuated as prompted by the authorities or the university. Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Wednesday seminar

Prague Set Theory Seminar
Dear all, There is no seminar tomorrow, Wednesday November 17th (state holiday). The seminar meets again on Wednesday November 24th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Adam Bartoš -- KPT correspondence in the context of weak Fraïssé categories The Kechris–Pestov–Todorčević correspondence states that a Fraïssé class of first-order structures has the Ramsey property if and only if the automorphism group of the Fraïssé limit is extremely amenable. We extend this correspondence to weak Fraïssé categories. This is a joint paper with Tristan Bice, Keegan Dasilva Barbosa, and Wiesław Kubiś (https://arxiv.org/abs/2110.01694). At the talk I will give a conceptual overview of the framework, present main ideas of the proofs, and if time permits, give examples in the realm of strong trees. Best, David

Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Speaker: Mohammad Golshani, IPM Date and Time: Friday, November 19, 2021 - 1:30pm to 2:30pm Location: https://zoom.us/j/92701726800 Abstract: I will discuss some recent joint projects with Saharon Shelah about the relation between ultraproducts and the continuum hypothesis. In particular, we show that the Keisler's isomorphism theorem implies the continuum hypothesis, and then prove some consistency results in the absence of the continuum hypothesis. ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

This Week in Logic at CUNY

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

- - - - Monday, Nov 15, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, November 15th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Rasmus Blanck, University of Gothenburg
Incompleteness results for arithmetically definable extensions of strong fragments of PA

In this talk, I will present generalisations of some incompleteness results along two axes: r.e. theories are replaced by -definable ones, and the base theory is pushed down as far as it will go below PA. Such results are often easy to prove from suitably formulated generalisations of facts used in the original proofs. I will present a handful of such facts, including versions of the arithmetised completeness theorem and the Orey–Hájek characterisation, to show what additional assumptions our theories must satisfy for the results to generalise. Two salient classes of theories emerge in this context: (a) -sound extensions of I + exp, and (b) -complete, consistent extensions of I. Finally, I will discuss some results that fail to generalise to -definable theories, as well as an open problem related to Woodin's theorem on the universal algorithm.

The presentation is based on the following paper: https://doi.org/10.1017/S1755020321000307




Logic and Metaphysics Workshop
Date: Tomorrow, Monday, November 15th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/ 
Speaker: Sara Uckelman (Durham)
Title: John Eliot’s Logick Primer: A bilingual English-Algonquian logic textbook

Abstract: In 1672 John Eliot, English Puritan educator and missionary, published The Logick Primer: Some Logical Notions to initiate the INDIANS in the knowledge of the Rule of Reason; and to know how to make use thereof [1]. This roughly 80 page pamphlet focuses on introducing basic syllogistic vocabulary and reasoning so that syllogisms can be created from texts in the Psalms, the gospels, and other New Testament books. The use of logic for proselytizing purposes is not distinctive: What is distinctive about Eliot’s book is that it is bilingual, written in both English and Massachusett, an Algonquian language spoken in eastern coastal and southeastern Massachusetts. It is one of the earliest bilingual logic textbooks, it is the only textbook that I know of in an indigenous American language, and it is one of the earliest printed attestations of the Massachusett language. In this talk, I will: (1) Introduce John Eliot and the linguistic context he was working in; (2) Introduce the contents of the Logick Primer—vocabulary, inference patterns, and applications; (3) Discuss notions of “Puritan” logic that inform this primer; (4) Talk about the importance of his work in documenting and expanding the Massachusett language and the problems that accompany his colonial approach to this work.

[1] J.[ohn] E.[liot]. The Logick Primer: Some Logical Notions to initiate the INDIANS in the knowledge of the Rule of Reason; and to know how to make use thereof. Printed by M. J., 1672.




- - - - Tuesday, Nov 16, 2021 - - - -

Computational Logic Seminar
Tuesday November 16, 2021, 2-4pm,  Eastern Time US
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Alessandra Palmigiano, Vrije Universiteit Amsterdam
Title: Non-distributive logics: from semantics to meaning.

Abstract: The term ‘non-distributive logics’ refers to the wide family of non-classical propositional logics in which the distributive laws α ∧(β ∨γ) ⊢ (α ∧β)∨(α ∧γ) and (α ∨β)∧(α ∨γ) ⊢ α ∨(β ∧γ) do not need to be valid. Since the rise of very well known instances such as quantum logic, interest in non-distributive logics has been building steadily over the years, motivated by insights from a range of fields in logic and neighbouring disciplines. Techniques and ideas have come from pure mathematical areas such as lattice theory, duality and representation, and areas in mathematical logic such as algebraic proof theory, but also from the philosophical and formal foundations of quantum physics, philosophical logic, theoretical computer science, and formal linguistics.

We will discuss an ongoing line of research in the relational (non topological) semantics of non-distributive logics, which is technically rooted in duality and (generalized) correspondence theory.

Not dissimilarly from the conceptual contribution of Kripke frames to the intuitive understanding of modal logics in various signatures, the relational semantics of non-distributive logics can help to illuminate the intuitive meaning of non-distributive logics at a more fundamental and conceptual level.

We discuss the application of the dual characterization methodology to introduce two relational semantic frameworks for non-distributive logics: the polarity-based frames and the graph-based frames. Despite their common root, polarity-based and graph-based semantics give rise to two radically different intuitive interpretations of non-distributive logics: namely, the polarity-based semantics supports the interpretation of non-distributive logics as logics of categories and formal concepts; the graph-based semantics supports a view of non-distributive logics as hyper-constructivist logics, i.e. logics in which the principle of excluded middle fails at the meta-linguistic level (in the sense that, at states in graph-based models, formulas can be satisfied, refuted or neither), and hence their propositional base generalizes intuitionistic logic in the same way in which intuitionistic logic generalizes classical logic. Consequently, we will argue that graph-based semantics supports the interpretation of non-distributive logics as logics of evidential reasoning.




- - - - Wednesday, Nov 17, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Time: Wednesdays 07:00 PM Eastern Time (US and Canada)
Speaker:     Marco Schorlemmer, Spanish National Research Council.




- - - - Thursday, Nov 18, 2021 - - - -



- - - - Friday, Nov 19, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 19, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Corey Switzer, University of Vienna

Definable Well Orders and Other Beautiful Pathologies

Many sets of reals - well orders of the reals, MAD families, ultrafilters on omega etc - only necessarily exist under the axiom of choice. As such, it has been a perennial topic in descriptive set theory to try to understand when, if ever, such sets can be of low definitional complexity. Large cardinals rule out such the existence of projective well orders, MAD families etc while it's known that if  (or even just 'every real is constructible') then there is a  well order of the reals and  witnesses to many other extremal sets of reals such as MAD families and ultrafilter bases. Recently a lot of work on the border of combinatorial and descriptive set theory has focused on considering what happens to the definitional complexity of such sets in models in which the reals have a richer structure - for instance when  fails and various inequalities between cardinal characteristics is achieved. In this talk I will present a recent advance in this area by exhibiting a model where the continuum is , there is a  well order of the reals, and a  MAD family, a  ultrafilter base for a P-point, and a  maximal independent family, all of size . These complexities are best possible for both the type of object and the cardinality hence this may be seen as a maximal model of 'minimal complexity witnesses'. This is joint work with Jeffrey Bergfalk and Vera Fischer.




Next Week in Logic at CUNY:

- - - - Monday, Nov 22, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, November 22th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Mauro di Nasso, Università di Pisa
Nonstandard natural numbers in arithmetic Ramsey Theory and topological dynamics

The use of nonstandard models *N of the natural numbers has recently found several applications in arithmetic Ramsey theory. The basic observation is that every infinite number in *N corresponds to an ultrafilter on N, and the algebra of ultrafilters is a really powerful tool in this field. Note that this notion also makes sense in any model of PA, where one can consider the 1-type of any infinite number.

Furthermore, nonstandard natural numbers are endowed with a natural compact topology, and one can apply the methods of topological dynamics considering the shift operator  . This very peculiar dynamic has interesting characteristics.

In this talk I will also present a new result in the style of Hindman’s Theorem about the existence of infinite monochromatic configurations in any finite coloring of the natural numbers. A typical example is the following monochromatic pattern:
a, b, c,  , a+b+ab, a+c+ac, b+c+bc,  , a+b+c+ab+ac+bc+abc.






Logic and Metaphysics Workshop
Date: Tomorrow, Monday, November 22th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Konstantinos Georgatos (John Jay).
Title: Similarity through indistinguishability: the geodesic reasoning on Kripke models

Abstract: Several logical operators, such as conditionals, revision, and merge, are often understood through the selection of most similar worlds. In applications, similarity is expressed with distance and “most similar” translates to “closest” using a distance metric. We shall argue that similarity may arise through an indistinguishability relation between possible worlds and employ the geodesic distance of such a model to measure closeness. This understanding allows us to define a variety of operators that correspond to merging and revising. I will present a few systems and representation results and will show that revision, merging, and conditioning are interdefinable thus, in effect, satisfying the Ramsey test.




- - - - Tuesday, Nov 23, 2021 - - - -



- - - - Wednesday, Nov 24, 2021 - - - -



- - - - Thursday, Nov 25, 2021 - - - -



- - - - Friday, Nov 26, 2021 - - - -




- - - - 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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Kamil Ryduchowski; An antiramsey coloring of pairs

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 16.11.2021, 13.30, room 105, Speaker: Kamil Ryduchowski (MIM UW) Title: "An antiramsey coloring of pairs " Abstact: "We present a fundamental theorem by Todorcevic, stating that there exists a coloring of the complete graph of the first uncountable cardinality in uncountably many colors without an uncountable monochromatic clique. We also discuss other results of Todorcevic of similar nature, which are in some sense multidimensional variants of that coloring". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) seminar talks Tuesday, November 16 and Thursday, November 18

Kurt Godel Research Center
The KGRC welcomes as guest: Radek Honzik (host: Vera Fischer) will visit the KGRC from November 14 to November 19 and give two talks (see below). * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, November 16 "Indestructibility of some compactness principles over models of PFA" Radek Honzik (Charles University in Prague, Czech Republic) Recall that the tree property at a regular cardinal kappa says that every kappa-tree has a cofinal branch, and the weak Kurepa hypothesis at kappa says that there exists a tree of size and height kappa which has at least kappa^+ cofinal branches. We will prove that over any transitive model of PFA, the tree property at omega_2 cannot be destroyed by the single Cohen forcing Add(omega,1) and the negation of the weak Kurepa hypothesis at omega_1 cannot be destroyed by a sigma-centered forcing. We will observe that a model-theoretic principle, Guessing model property (GMP), is enough for the preservation results. GMP can be formulated also for larger cardinals. We will give an application of our result by showing that there is a model in which the negation of the weak Kurepa hypothesis holds at aleph_{omega+1}. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 8 1st floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the lectures we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! * * * Logic Colloquium Kurt Gödel Research Center Thursday, November 18 "Compactness at small uncountable cardinals" Radek Honzik (Charles University in Prague, Czech Republic) We will discuss various compactness principles such as stationary reflection, the tree property or Rado conjecture at small cardinals (for instance omega_2). We will give context and motivation for the principles and discuss and compare the main sources of these principles: large cardinals and consequences of forcing axioms. We will focus on indestructibility of these principles with respect to classes of forcing notions, and give some examples (for instance we show that stationary reflection at omega_2 cannot be destroyed by a ccc forcing). Indestructibility is important for investigating connections between compactness and other areas of set theory such as generalized cardinal invariants, and we will mention some applications. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the talk we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Two talks next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, November 16, 2021 Mathematical logic seminar: 3:30 P.M., Online, William Chan, Carnegie Mellon University Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 Title: Almost Disjoint Families under Determinacy, part 1 Abstract: We will investigate some properties of almost disjoint families and the maximal almost disjoint (MAD) family problem on cardinals (regular and singular) within determinacy settings. We will show under suitable assumptions that every almost disjoint family on a cardinal of uncountable cofinality must be wellorderable. This will show under suitable assumptions (which includes the boldface GCH) that there are no MAD families on a regular cardinal kappa so that the family does not strictly inject into kappa. (This answers a question of Muller concerning uncountable MAD families on omega_1 under AD.) We will show under AD that every wellorderable almost disjoint family on a cardinal below Theta of countable cofinality is not maximal. This result may help explain why the Schrittesser-Tornquist or Neeman-Norwood arguments excluding a MAD family on omega has quite a different flavor than the MAD family question for cardinals of uncountable cofinality. We will review the ultrapower representation and measure analysis of Jackson below omega_omega. This will be used to investigate the MAD family question surrounding omega_1, omega_2, and the singular cardinals omega_n for n between 3 and omega. This is joint work with Stephen Jackson and Nam Trang. TUESDAY, November 16, 2021 Set Theory Reading Group: 4:30 P.M., Online, William Chan, Carnegie Mellon University Title: Almost Disjoint Families under Determinacy, part 2 Abstract: We will investigate some properties of almost disjoint families and the maximal almost disjoint (MAD) family problem on cardinals (regular and singular) within determinacy settings. We will show under suitable assumptions that every almost disjoint family on a cardinal of uncountable cofinality must be wellorderable. This will show under suitable assumptions (which includes the boldface GCH) that there are no MAD families on a regular cardinal kappa so that the family does not strictly inject into kappa. (This answers a question of Muller concerning uncountable MAD families on omega_1 under AD.) We will show under AD that every wellorderable almost disjoint family on a cardinal below Theta of countable cofinality is not maximal. This result may help explain why the Schrittesser-Tornquist or Neeman-Norwood arguments excluding a MAD family on omega has quite a different flavor than the MAD family question for cardinals of uncountable cofinality. We will review the ultrapower representation and measure analysis of Jackson below omega_omega. This will be used to investigate the MAD family question surrounding omega_1, omega_2, and the singular cardinals omega_n for n between 3 and omega. This is joint work with Stephen Jackson and Nam Trang.

Logic Seminar 10 Nov 2021 16:00 hrs by Manat Mustafa, Nazarbayev University, Kazakhstan

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 10 November 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Manat Mustafa Title: Rogers semilattices of punctual numberings URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The talk employs the punctuality paradigm in the studies of numberings. We consider the punctual numberings, i.e. uniform computations for families of primitive recursive functions. The punctual reducibility between numberings is induced by primitive recursive functions. This approach gives rise to upper semilattices of degrees, which are called Rogers pr-semilattices. The main focus of the talk will be the structural properties of Rogers pr-semilattices. We will show several examples, which highlight further contrasts between the punctual framework and the classical theory of computable numberings. All results are obtained in joint work with Nikolay Bazhenov and Sergei Ospichev.

This Week in Logic at CUNY

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

- - - - Monday, Nov 8, 2021 - - - -

Logic and Metaphysics Workshop
Date: Tomorrow, Monday, November 8th, 4.15-6.15 (NY time)
Speaker: Roman Kossak (CUNY GC)
Title: How undefinable is truth?

Abstract: Almost any set of natural numbers you can think of is first-order definable in the standard model of arithmetic. A notable exception is the set Tr of Gödel numbers of true first-order sentences about addition and multiplication. On the one hand—by Tarski’s undefinability of truth theorem—Tr has no first order definition in the standard model; on the other, it has a straightforward definition in the form of an infinite disjunction of first order formulas. It is definable in a very mild extension of first-order logic. In 1963, Abraham Robinson initiated the study of possible truth assignments for sentences in languages represented in nonstandard models of arithmetic. Such assignments exist, but only in very special models; moreover they are highly non-unique, and—unlike Tr—they are not definable any  reasonable formal system. In the talk, I will explain some model theory behind all that and I will talk about  some recent results in the study of axiomatic theories of truth.





- - - - Tuesday, Nov 9, 2021 - - - -


Computational Logic Seminar
Tuesday November 9, 2021, 2-4pm,  Eastern Time US
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Tuesday November 9, 2021.

Speaker: Antonis Achilleos, Reykjavik University
Title: Adventures in Monitorability

Abstract:
I will present recent work on runtime monitorability. Runtime Verification (RV) is the technique of using a monitor to detect the violation or satisfaction of a property at runtime. One question that we ask is what properties we can monitor for. But even before giving an answer, we must first understand what that question means. Although many monitorability definitions exist, few are defined explicitly in terms of the operational guarantees provided by monitors, ie, the computational entities carrying out the verification. We view monitorability as a spectrum, where the fewer guarantees that are required of monitors, the more properties become monitorable. Accordingly, we present a monitorability hierarchy based on this trade-off..
For regular, linear-time specifications, we give syntactic characterisations of the hierarchy in Hennessy-Milner logic with recursion. 

We then compare the obtained fragments with previous results for the branching-time setting.

This is joint work with Luca Aceto, Adrian Francalanza, Anna Ingólfsdóttir, and Karoliina Lehtinen.





- - - - Wednesday, Nov 10, 2021 - - - -



- - - - Thursday, Nov 11, 2021 - - - -



- - - - Friday, Nov 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 12, 1pm
The seminar will take place virtually at 1pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property II

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.





Next Week in Logic at CUNY:

- - - - Monday, Nov 15, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, November 15th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Rasmus Blanck, University of Gothenburg
Incompleteness results for arithmetically definable extensions of strong fragments of PA

In this talk, I will present generalisations of some incompleteness results along two axes: r.e. theories are replaced by -definable ones, and the base theory is pushed down as far as it will go below PA. Such results are often easy to prove from suitably formulated generalisations of facts used in the original proofs. I will present a handful of such facts, including versions of the arithmetised completeness theorem and the Orey–Hájek characterisation, to show what additional assumptions our theories must satisfy for the results to generalise. Two salient classes of theories emerge in this context: (a) -sound extensions of I + exp, and (b) -complete, consistent extensions of I. Finally, I will discuss some results that fail to generalise to -definable theories, as well as an open problem related to Woodin's theorem on the universal algorithm.

The presentation is based on the following paper: https://doi.org/10.1017/S1755020321000307





- - - - Tuesday, Nov 16, 2021 - - - -



- - - - Wednesday, Nov 17, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Time: Wednesdays 07:00 PM Eastern Time (US and Canada)
Speaker:     Marco Schorlemmer, Spanish National Research Council.




- - - - Thursday, Nov 18, 2021 - - - -



- - - - Friday, Nov 19, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 19, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Corey Switzer, University of Vienna




- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

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Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Yaroslav D. Sergeyev (University of Calabria)
TITLE: Some paradoxes of Infinity revisited
DATE: 10 November 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.







Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


(KGRC) Set Theory Research Seminar talk on Tuesday, November 9

Kurt Godel Research Center
The KGRC welcomes as guests: Jaroslav Šupina (host: Serhii Bardyla) will stay until November 9. Fortunato Maesano (host: Lyubomyr Zdomskyy) will stay until June 30, 2022. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, November 9 "The Special Tree Number" Corey Switzer (KGRC) A tree $T$ of height $\omega_1$ with no uncountable branch is {\em special} if there is a function $f:T \to \omega$ which is injective on chains. It's well known that under $\mathrm{MA} + \neg \CH$ every tree of height $\omega_1$ with no uncountable branch of size less than the continuum is special, while in $\mathrm{ZFC}$ one can construct a non-special tree of height $\omega_1$ with no uncountable branch. At the same time there may be a Souslin tree while the continuum is as large as you like thus providing a model with a small non-special tree. These facts together suggest a new cardinal characteristic, the special tree number, denote $\mathfrak{st}$: the least size of a tree of height $\omega_1$ with no uncountable branch which is not special. By what was observed above, $\mathrm{MA} + \neg \CH$ implies that $\mathfrak{st} = 2^{\aleph_0}$ while it is consistent that $mathfrak{st} < 2^{\aleph_0}$ with the latter arbitrarily large. In this talk we will introduce the basic properties of $\mathfrak{st}$ and prove in particular that it is consistent on the one hand that $\mathfrak{st}$ is $\aleph_1$ while essentially all well-studied cardinal characteristics are arbitrarily large and on the other hand it is consistent that for any regular $\kappa$ we have $\mathfrak{a} = {\rm non}(\mathcal M) = \aleph_1 < \mathfrak{st} = {\rm cov}(\mathcal M) = 2^{\aleph_0} = \kappa$. In other words, $\mathfrak{st}$ is independent of the lefthand side of Cicho\'{n}'s diagram, $\mathfrak{p}$ and $\mathfrak{a}$. The latter model involves a careful analysis of reals added by the standard ccc forcing to specialize trees, which may be of independent interest. This is a relatively new investigation and there are many open questions I hope to discuss as well, time permitting. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 8 1st floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the lectures we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Please note that tomorrow's Set Theory Seminar meeting starts at 1pm (not 2pm as stated in the previous email).

Best,
Jonas


This Week in Logic at CUNY:

- - - - Friday, Nov 5, 2021 - - - -

Philog Seminar
Friday, November 5, 2021, 10:30 AM (New York time)
(Zoom link will be posted on https://philog.arthurpaulpedersen.org/)
Sonja Smets, University of Amsterdam
Title: Computing Social Behavior
 
Abstract:  Recently, epistemic-social phenomena have received more attention from the logic community, analyzing peer pressure, studying informational cascades, inspecting priority-based peer influence, modeling diffusion and prediction, and examining reflective social influence. In this presentation, I will contribute to this line of work and focus in particular on the logical features of social group creation. I pay attention to the mechanisms which indicate when agents can form a team based on the correspondence in their set of features (behavior, opinions, etc.). Our basic approach uses a semi-metric on the set of agents, which is used to construct a network topology. This structure is then extended with epistemic features to represent the agents' epistemic states, allowing us to explore group-creation alternatives where what matters is not only the agent's differences but also what they know about them. The logical settings in this work make use of the techniques of dynamic epistemic logic to represent group-creation actions, to define new languages in order to describe their effects, and to provide sound and complete axiom systems. This talk is based on joint work with Fernando Velazquez Quesada.

Sonja Smets is a Belgian and Dutch logician and epistemologist known for her work in belief revision and quantum logic. She is Professor of Logic and Epistemology at the University of Amsterdam, where she directed the university's Institute for Logic, Language and Computation and is affiliated with both the Faculty of Science and the Department of Philosophy.




Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 5, 2pm
The seminar will take place virtually at 1pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.








Next Week in Logic at CUNY:

- - - - Monday, Nov 8, 2021 - - - -



- - - - Tuesday, Nov 9, 2021 - - - -



- - - - Wednesday, Nov 10, 2021 - - - -



- - - - Thursday, Nov 11, 2021 - - - -



- - - - Friday, Nov 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 12, 1pm
The seminar will take place virtually at 1pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property II

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

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

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Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday November 10th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Paul Szeptycki -- An example from a square-sequence, convergence and the G_delta-topology, part 2. Questions of Bella concerning cardinal invariants of the G_delta topology and questions of Arhangel'skii on strong convergence properties are answered with examples constructed from square(kappa) sequences. Best, David

Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: https://zoom.us/j/92701726800 Friday, November 5, 2021 - 12:30pm to 2:00pm ------------------------------------------------------------------- Speaker: Philip Welch, University of Bristol Title: The universe constructed from a set (or class) of regular cardinals. Abstract: We continue some work on L[Card] (the universe constructed from the predicate for the cardinals) to look at L[Reg] where Reg is the class of uncountable regular cardinals. The latter is also a model of a rich combinatorial structure being, as it turns out, a Magidor iteration of Prikry forcings (using recent work of Ben-Neria). But it is limited in size, in fact is a rather 'thin' model. We show, letting O^s = O^sword be the least iterable structure with a measure which concentrates on measurable cardinals: Theorem (ZFC) (a) Let S be a set, or proper class, of regular cardinals, then O^s is not an element of L[S]. (b) This is best possible, in that no smaller mouse M can be substituted for O^s. (c) L[S] is a model of: GCH, Square's, Diamonds, Morasses etc and has Ramsey cardinals, but no measurable cardinals. ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Toronto Set Theory Seminar // Nov 5 UNUSUAL TIME 12:30 // Philip Welch

Set Theory Seminar at the Fields Institute
Dear All, I would like to invite you to this week's Toronto Set Theory Seminar at the Fields Institute. Careful, we start early this week, at 12:30 ! https://zoom.us/j/92701726800 ----- Speaker: Philip Welch, University of Bristol Date and Time: Friday, November 5, 2021 - 12:30pm to 2:00pm Title: The universe constructed from a set (or class) of regular cardinals. Abstract: We continue some work on L[Card] (the universe constructed from the predicate for the cardinals) to look at L[Reg] where Reg is the class of uncountable regular cardinals. The latter is also a model of a rich combinatorial structure being, as it turns out, a Magidor iteration of Prikry forcings (using recent work of Ben-Neria). But it is limited in size, in fact is a rather 'thin' model. We show, letting O^s = O^sword be the least iterable structure with a measure which concentrates on measurable cardinals: Theorem (ZFC) (a) Let S be a set, or proper class, of regular cardinals, then O^s is not an element of L[S]. (b) This is best possible, in that no smaller mouse M can be substituted for O^s. (c) L[S] is a model of: GCH, Square's, Diamonds, Morasses etc and has Ramsey cardinals, but no measurable cardinals. ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

Oct 15 // Toronto Set Theory Seminar // Yinhe Peng - On Scheepers' conjecture and Scheepers' Diagram

Set Theory Seminar at the Fields Institute
Dear All, The Toronto Set Theory Seminar is resuming; I would like to invite you to our next talk! Friday Oct 15, 13:30 Eastern Daylight Time (GMT-4) at https://zoom.us/j/92701726800 ----- Speaker: Yinhe Peng, Chinese Academy of Science Title: On Scheepers' conjecture and Scheepers' Diagram Abstract: We first refute Scheepers' conjecture. More precisely, we prove the following: Assuming CH, there is a subset of reals X such that C_p(X) has property (α_2) and X does not satisfy S_1(Γ,Γ). It is known that by Dow and Hales' results, Scheepers' conjecture is consistent. So some additional assumption is needed. We will reveal the idea and some details. All but two implications are known in Scheepers Diagram. We then complete Scheepers Diagram by proving the following: U_fin(Γ,Γ) implies S_fin(Γ,Ω). U_fin(Γ,Ω) does not imply S_fin(Γ,Ω). More precisely, assuming CH, there is a subset of reals X satisfying U_fin(Γ,Ω) such that X does not satisfy S_fin(Γ,Ω). ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

Oct 15 // Toronto Set Theory Seminar // Yinhe Peng - On Scheepers' conjecture and Scheepers' Diagram

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar Friday Oct 15, 13:30 Eastern Daylight Time (GMT-4) https://zoom.us/j/92701726800 ----- Speaker: Yinhe Peng, Chinese Academy of Science Title: On Scheepers' conjecture and Scheepers' Diagram Abstract: We first refute Scheepers' conjecture. More precisely, we prove the following: Assuming CH, there is a subset of reals X such that C_p(X) has property (α_2) and X does not satisfy S_1(Γ,Γ). It is known that by Dow and Hales' results, Scheepers' conjecture is consistent. So some additional assumption is needed. We will reveal the idea and some details. All but two implications are known in Scheepers Diagram. We then complete Scheepers Diagram by proving the following: U_fin(Γ,Γ) implies S_fin(Γ,Ω). U_fin(Γ,Ω) does not imply S_fin(Γ,Ω). More precisely, assuming CH, there is a subset of reals X satisfying U_fin(Γ,Ω) such that X does not satisfy S_fin(Γ,Ω).

Oct 15 9am // Yinhe Peng - On Scheepers' conjecture and Scheepers' Diagram

Set Theory Seminar at the Fields Institute
Dear All, Sorry, my last email had a wrong starting time. Yinhe's talk will be at 9am ! That is, Friday Oct 15, 9:00 am Eastern Daylight Time (GMT-4) at https://zoom.us/j/92701726800 ----- Speaker: Yinhe Peng, Chinese Academy of Science Title: On Scheepers' conjecture and Scheepers' Diagram Abstract: We first refute Scheepers' conjecture. More precisely, we prove the following: Assuming CH, there is a subset of reals X such that C_p(X) has property (α_2) and X does not satisfy S_1(Γ,Γ). It is known that by Dow and Hales' results, Scheepers' conjecture is consistent. So some additional assumption is needed. We will reveal the idea and some details. All but two implications are known in Scheepers Diagram. We then complete Scheepers Diagram by proving the following: U_fin(Γ,Γ) implies S_fin(Γ,Ω). U_fin(Γ,Ω) does not imply S_fin(Γ,Ω). More precisely, assuming CH, there is a subset of reals X satisfying U_fin(Γ,Ω) such that X does not satisfy S_fin(Γ,Ω). ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

TOMORROW // Toronto Set Theory Seminar // Stefan Hoffelner - On Scheepers' conjecture and Scheepers' Diagram

Set Theory Seminar at the Fields Institute
Dear All, Please allow me to invite you to tomorrow's Toronto Set Theory Seminar at the Fields Institute, at https://zoom.us/j/92701726800 ----- Speaker: Stefan Hoffelner, University of Münster Date and Time: Friday, October 29, 2021 - 1:30pm to 3:00pm Title: Forcing and the Separation, the Reduction and the Uniformization property. Abstract: The Separation property, the Reduction property and the Uniformization property, introduced in the 1920's and 1930's are three classical regularity properties of pointclasses on the reals. The celebrated results of Y. Moschovakis on the one hand and D. Martin, J. Steel and H. Woodin on the other, yield a global description of the behaviour of these regularity properties for projective pointclasses under the assumption of large cardinals. In particular, under PD, for every natural number n, Π12n+1 -sets and hence Σ12n+2 -sets do have the Uniformization property (and therefore the weaker Reduction property and the Separation property for the dual pointclass). Yet the question of universes which display an alternative behaviour of theses regularity properties has remained a complete mystery, mostly due to the absence of forcing techniques to produce such models. Indeed, even the question of the forceability of a universe where the Σ13 Separation property holds was a well-known open problem since 1968. In my talk, I want to outline some recently obtained techniques, which turn the question of a universe with, say, the Π13 Reduction property into a fixed point problem for certain sets of forcing notions. This fixed point problem can be solved, yielding a specific set of forcing notions which in turn can be used to force the Π1n Reduction property or, with more complicated techniques, the Π1n Uniformization property (for n>2) over fine structural inner models with large cardinals (for n=3, the inner model is just L). For even n, these universes outright contradict the PD-induced pattern, for odd n these universes give new lower bounds in terms of consistency strength. ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

TOMORROW // Toronto Set Theory Seminar // Stefan Hoffelner // Forcing and the Separation, the Reduction and the Uniformization-property

Set Theory Seminar at the Fields Institute
Dear All, Correction: Now with correct title in the subject line, sorry about that! https://zoom.us/j/92701726800 ----- Speaker: Stefan Hoffelner, University of Münster Date and Time: Friday, October 29, 2021 - 1:30pm to 3:00pm Title: Forcing and the Separation, the Reduction and the Uniformization property. Abstract: The Separation property, the Reduction property and the Uniformization property, introduced in the 1920's and 1930's are three classical regularity properties of pointclasses on the reals. The celebrated results of Y. Moschovakis on the one hand and D. Martin, J. Steel and H. Woodin on the other, yield a global description of the behaviour of these regularity properties for projective pointclasses under the assumption of large cardinals. In particular, under PD, for every natural number n, Π12n+1 -sets and hence Σ12n+2 -sets do have the Uniformization property (and therefore the weaker Reduction property and the Separation property for the dual pointclass). Yet the question of universes which display an alternative behaviour of theses regularity properties has remained a complete mystery, mostly due to the absence of forcing techniques to produce such models. Indeed, even the question of the forceability of a universe where the Σ13 Separation property holds was a well-known open problem since 1968. In my talk, I want to outline some recently obtained techniques, which turn the question of a universe with, say, the Π13 Reduction property into a fixed point problem for certain sets of forcing notions. This fixed point problem can be solved, yielding a specific set of forcing notions which in turn can be used to force the Π1n Reduction property or, with more complicated techniques, the Π1n Uniformization property (for n>2) over fine structural inner models with large cardinals (for n=3, the inner model is just L). For even n, these universes outright contradict the PD-induced pattern, for odd n these universes give new lower bounds in terms of consistency strength. ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

This Week in Logic at CUNY

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

- - - - Monday, Nov 1, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, October 25th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Fedor Pakhomov Ghent University
Finitely Axiomatized Theories Lack Self-Comprehension

This is a joint work with Albert Visser. We prove that no consistent finitely axiomatized theory one-dimensionally interprets its own extension with predicative comprehension. This constitutes a result with the flavor of the Second Incompleteness Theorem whose formulation is completely arithmetic-free. Probably the most important novel feature that distinguishes our result from the previous results of this kind is that it is applicable to arbitrary weak theories, rather than to extensions of some base theory. The methods used in the proof of the main result yield a new perspective on the notion of sequential theory, in the setting of forcing-interpretations. https://arxiv.org/abs/2109.02548 




Logic and Metaphysics Workshop
Date: Monday, November 1, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/ 
Thomas M Ferguson (Amsterdam)
The Subject-Matter of Modal Sentences

The framework of topic-sensitive intentional modal operators (TSIMs) described by Berto provides a general platform for representing agents' intentional states of various kinds. For example, a TSIM can model doxastic states, capturing a notion that given the acceptance of antecedent information P, an agent will have a consequent belief Q. Notably, the truth conditions for TSIMs include a subject-matter filter so that the topic of the consequent Q must be "included" within that of the antecedent. To extend the account to languages with richer expressivity thus requires an expanded account of subject-matter. In this talk, I will discuss extending earlier work on the subject-matter of intensional conditionals to the special case of modal sentences whose primary operators are interpreted by possible worlds semantics.



- - - - Tuesday, Nov 2, 2021 - - - -

Computational Logic Seminar
Tuesday November 2, 2021, 2-4pm Eastern Time US
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Stipe Pandzic, Utrecht University
Title: Non-monotonic reasoning and defeasible argumentation in justification logic

Abstract: In the 1980s, John Pollock’s work on defeasible reasons started the quest in the AI community for a formal system of defeasible argumentation. My goal in this talk is to present a logic of structured defeasible argumentation using the language of justification logic. One of the key features that is absent in standard justification logics is the possibility to weigh different epistemic reasons or pieces of evidence that might conflict with one another. To amend this, we develop a semantics for “defeaters”: conflicting reasons forming a basis to doubt the original conclusion or to believe an opposite statement.

Formally, non-monotonicity of reasons is introduced through default rules with justification logic formulas. The new logic manipulates defeasible justification assertions of the type t :F that read as “t is a defeasible reason that justifies F”. Such formulas are then interpreted as arguments and their acceptance semantics is given in analogy to Dung’s abstract argumentation framework semantics. In contrast to argumentation frameworks, however, determining arguments’ acceptance in default justification logic simply turns into finding (non-monotonic) logical consequences from a starting theory with justification assertions.

As one of the important results, we can show that a large subclass of Dung’s frameworks is a special case of default justification logic in the sense that (1) Dung’s frameworks can be obtained from justification logic-based theories by focusing on a single aspect of attacks among justification logic arguments (in analogy to “forgetful projection” for standard justification logic) and (2) Dung’s warranted frameworks always have multiple justification logic instantiations called “realizations”. By the end of the talk, I show how default justification logic unifies all three standard types of argumentative attack in AI, namely rebutting, undercutting and undermining attacks, as a first logic of this kind.




- - - - Wednesday, Nov 3, 2021 - - - -



- - - - Thursday, Nov 4, 2021 - - - -



- - - - Friday, Nov 5, 2021 - - - -

Philog Seminar
Friday, November 5, 2021, 10:30 AM
(Zoom link will be posted on https://philog.arthurpaulpedersen.org/)
Sonja Smets, University of Amsterdam
Title: Computing Social Behavior
 
Abstract:  Recently, epistemic-social phenomena have received more attention from the logic community, analyzing peer pressure, studying informational cascades, inspecting priority-based peer influence, modeling diffusion and prediction, and examining reflective social influence. In this presentation, I will contribute to this line of work and focus in particular on the logical features of social group creation. I pay attention to the mechanisms which indicate when agents can form a team based on the correspondence in their set of features (behavior, opinions, etc.). Our basic approach uses a semi-metric on the set of agents, which is used to construct a network topology. This structure is then extended with epistemic features to represent the agents' epistemic states, allowing us to explore group-creation alternatives where what matters is not only the agent's differences but also what they know about them. The logical settings in this work make use of the techniques of dynamic epistemic logic to represent group-creation actions, to define new languages in order to describe their effects, and to provide sound and complete axiom systems. This talk is based on joint work with Fernando Velazquez Quesada.

Sonja Smets is a Belgian and Dutch logician and epistemologist known for her work in belief revision and quantum logic. She is Professor of Logic and Epistemology at the University of Amsterdam, where she directed the university's Institute for Logic, Language and Computation and is affiliated with both the Faculty of Science and the Department of Philosophy.




Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 5, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.








Next Week in Logic at CUNY:

- - - - Monday, Nov 8, 2021 - - - -



- - - - Tuesday, Nov 9, 2021 - - - -



- - - - Wednesday, Nov 10, 2021 - - - -



- - - - Thursday, Nov 11, 2021 - - - -



- - - - Friday, Nov 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 12, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property II

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
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Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

The next session of the Barcelona Set Theory Semina will take place tomorrow: 

SPEAKER:   Sean Cox (Virginia Commonwealth University)
TITLE: Homological algebra, elementary submodels, and stationary logic