Set Theory Talks

KGRC talks on October 23

Kurt Godel Research Center

10/17/2025 8:16:45

KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14 – 16, 1090, 1st floor, SR 10 Thursday, October 23, 11:30 am – 1:00 pm “Preservation of the left side of Cichoń’s diagram” T. Goto (TU Wien) In the context of countable support iterations, there are two significant preservation theorems. The First Preservation Theorem, due to Shelah, preserves the dominating number of a $F_\sigma$ relation small. The Second Preservation Theorem, due to Judah–Repický, preserves the bounding number of a $F_\sigma$ relation small. It is usual to use The First Preservation Theorem to preserve the right side of Cichoń’s diagram and to use The Second Preservation Theorem to preserve the left side of Cichoń’s diagram. But sometimes The Second Preservation Theorem is inconvenient since it does not help at successor steps. Then we develop methods using The First Preservation Theorem to preserve the left side of Cichoń’s diagram. This method also yields several new constellations of cardinal invariants, which we shall introduce. This is joint work with Diego Mejía. Please direct any questions about this talk to Vera Fischer (vera.fischer@univie.ac.at). If you would like to attend online, please send an email to info@logic.univie.ac.at. * * * * * * * * * Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11 Thursday, October 23, 3:00 pm – 3:50 pm “Manifold classification from the descriptive viewpoint” I. Smythe (U of Winnipeg, CA) We describe a unified descriptive set-theoretic framework for studying the complexity of classification problems for finite-dimensional manifolds. We establish several precise complexity results, such as for the classification of surfaces up to homeomorphism and for classes of hyperbolic manifolds up to isometry. The latter is intimately connected with the conjugation actions of certain Lie groups on their spaces of discrete subgroups. This work is joint with Jeffrey Bergfalk. Please direct any questions about this talk to Matthias Aschenbrenner (matthias.aschenbrenner@univie.ac.at). If you would like to attend online, please send an email to info@logic.univie.ac.at. * * * * * * * * * New video recording available from the Set Theory Seminar: October 16: L. Notaro (U Wien) “Ladders and Squares”. https://ucloud.univie.ac.at/index.php/s/gSt4gtoRiR7f9Rx --- Kurt Gödel Research Center Logic Group University of Vienna - Faculty of Mathematics Kolingasse 14-16 1090 Vienna Austria +43 (0) 1 / 4277-50501 https://kgrc.univie.ac.at

KGRC Set Theory talk November 7

Kurt Godel Research Center

11/5/2024 6:16:33

KGRC/Institute of Mathematics invites you to the following talk: Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, November 7, 11:30am--1:00pm, hybrid mode "Games and chromatic numbers of analytic graphs" David Chodounský (Czech Academy of Sciences, Prague, CZ) We define games which characterize countable coloring numbers of analytic graphs on Polish spaces. These games can provide simple verification of the countable chromatic number of certain graphs. We also get a simpler proof of a dichotomy originally proved by Adams and Zapletal: If an analytic graph has an uncountable coloring number, then it contains the graph $\Delta_0$ as a subgraph. (Here the graph $\Delta_0$ is a certain simple graph with uncountable coloring number.) Joint work with Jindrich Zapletal. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recordings available so far of the Set Theory Seminar: Oct 29: P. Lücke, Hamburg, DE: "Very large cardinals and ordinal definability" https://ucloud.univie.ac.at/index.php/s/9eaDnTCPBXJwGR5 * * * * * * * * * Video recording available so far of the Logic Colloquium: Oct 31: M. Malicki, Warsaw, PL: "Continuous logic and equivalence relations" https://ucloud.univie.ac.at/index.php/s/KM94ga9xSewfZXR * * * * * * * * * Updates at https://kgrc.univie.ac.at/eventsnews/ -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

Cross-Alps Logic Seminar (speaker: Raphaël Carroy)

Cross-Alps Logic Seminar

11/6/2024 17:33:00

On Friday 08.11.2024 at 16.00 CET

Raphaël Carroy (Università di Torino)

will give a talk on

A well-quasi-order for continuous functions

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

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

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

All the best,
Vincenzo

Wednesday seminar, MLTCS colloquium, Prague--Vienna set theory workshop

Prague Set Theory Seminar

11/8/2024 6:59:57

Dear all, ************************************************************************ The seminar meets on Wednesday November 13th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Hannes Jakob (University of Freiburg) -- On Friedman's Property and Stationary Reflection For a regular cardinal $\kappa\geq\omega_2$, the property $F(\kappa)$ states that any subset of $\kappa$ contains or is disjoint from a closed set of ordertype $\omega_1$. Two related properties are $SR(\kappa)$ which states that any stationary subset of $\kappa$ has a stationary initial segment and $F^+(\kappa)$ which states that any stationary subset of $\kappa$ consisting of ordinals of countable cofinality has an initial segment which is club. In this talk, we will introduce posets which add witnesses to the failures of the preceding properties and use them in two ways: In the first part of the talk we will show that they have different ``meta-properties'' which appear in the attributes of the corresponding posets and in the provable effect certain large cardinals have on their possible patterns. In the second part of the talk we will introduce further variants of the properties $F$ and $F^+$ and completely determine the provable implications between them by introducing a maximal variant of Martin's Maximum which implies the failure of some variants while implying the truth of others. ************************************************************************ The joint logic seminar/colloquium of the MLTCS department will take place on Monday November 11th in the Institute of Mathematics CAS, Zitna 25, blue lecture hall, ground floor, rear building. We start at 16:15 with coffee and cakes and continue with the lecture at 16:30. After the talk we will go to a pub. Program: Pedro Marun -- Lindelöf trees The study of trees commenced with work of Kurepa on a problem of Souslin. Since then, trees have cemented themselves as one of the cornerstones of modern set theory, both as a tool to prove theorems and as inherently interesting objects, the key realization being that König’s Lemma no longer holds in the uncountable realm. The goal of this talk is to discuss Lindelöf trees: trees of height omega_1 with countable levels which are infinitely splitting and have no uncountable finitely splitting subtrees. We will mention how this notion relates to other properties of trees and go over some provability and independence facts. ************************************************************************ The Prague--Vienna Set Theory Workshop will take place on Friday November 15th, Faculty of Arts, Charles University, Celetna 20. A tentative program of the workshop attached. ************************************************************************ Best, David

KGRC Set Theory Talk, November 14

Kurt Godel Research Center

11/8/2024 9:50:24

KGRC/Institute of Mathematics invites you to the following talks: updates at https://kgrc.univie.ac.at/eventsnews/ Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, November 14, 11:30am--1:00pm, hybrid mode "Turing-invariant functions under determinacy I" B. Siskind (TU Wien) This talk is part of a two-part series. In part~1, we will discuss some results about Turing-invariant functions from reals into $\omega_1$ under the Axiom of Determinacy. In part~2 on November~21, we'll see how these results can be used to prove Martin's Conjecture for order-preserving functions up to the double hyperjump (and some other related things, time permitting). Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recording available so far of the Set Theory Seminar: Nov 7: David Chodounský (Czech Academy of Sciences, Prague, CZ): "Games and chromatic numbers of analytic graphs". https://ucloud.univie.ac.at/index.php/s/bB9Yw6fCXRzffQz -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

11/10/2024 22:32:00

This Week in Logic at CUNY:

- - - - Monday, Nov 11, 2024 - - - -

Rutgers Logic Seminar
Monday November 11, 3:30pm, Rutgers University, Hill Center, Hill 705

Frank Wagner, Ohio State

Logic and Metaphysics Workshop
Date: Monday, November 11, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Friederike Moltmann (CNRS).
Title: On the ontology and semantics of absence

Abstract: This talk proposes a new semantic analysis of verbs of absence such as ‘lack’ and ‘be missing’. The semantics is based on the notion of a conceptual whole and its (conceptual) parts, which generates both variable embodiments (of the whole and its structural parts) and modal objects of the sort of a ‘lack’. It involves an extension of truthmaker semantics (applied to modal objects) where truthmakers (satisfiers) now include parts of wholes. The talk rehabilitates entities of the sort of ‘lacks’ often subject to ridicule, most notoriously by Chomsky.

- - - - Tuesday, Nov 12, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, November 12, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Piotr Gruza, University of Warsaw

Separations between categoricity-like properties of first-order theories: part II

A theory is tight if and only if every two extensions of it, in the language of that theory, are bi-interpretable iff they are equal. The property of being tight can be seen as a kind of local categoricity in a suitable category of theories and interpretations. Examples of tight theories include $PA$ , $Z 2$ , $ZF$ , and $KM$ . Neatness, semantic tightness, and solidity are strengthenings of tightness, with solidity being the strongest and the other two being intermediate. During the talk we will focus on relations between those properties in the context of arithmetic theories and theories of finite sets.

Partly based on a joint work with Leszek Kołodziejczyk and Mateusz Łełyk.

- - - - Wednesday, Nov 13, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:    Emilio Minichiello, CUNY CityTech.
Date and Time:     Wednesday November 13, 2024, 7:00 - 8:30 PM.IN-PERSON TALK. CUNY Graduate Center Room 6417
Title:     Decision Problems on Graphs with Sheaves.

Abstract: This semester I don’t feel like talking about my research. Instead I’ll talk about what I’ve learned from reading the paper Compositional Algorithms on Compositional Data: Deciding Sheaves on Presheaves by Althaus, Bumpus, Fairbanks and Rosiak. This paper is about how we can use sheaf theory to break apart a computational problem, solve it on small pieces, and then glue the solutions together to get a global solution to the computational problem. I’ll go through the main ideas of this paper, using the category of simple graphs with monomorphisms as a main example to showcase their results.

- - - - Thursday, Nov 14, 2024 - - - -

- - - - Friday, Nov 15, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, November 15, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Philipp Schlicht Kurt Gödel Research Center

Logic Workshop
CUNY Graduate Center
Friday, November 15, 2:00pm-3:30pm, Room 4419

Russell Miller, CUNY
Computable reductions on groups and fields

Hjorth and Thomas established that the complexity of the isomorphism problem for torsion-free abelian groups of finite rank grows dramatically higher as the rank increases: for each , there is no Borel function that maps each rank- group to a rank- group in such a way that . We say that there is no Borel reduction from isomorphism on to isomorphism on . (From lower to higher rank, in contrast, such a reduction is readily seen.) Fields of transcendence degree over have very similar computability properties to groups in . This being so, we extend their investigations to include the isomorphism relations on the classes of such fields. We show that there do exist reductions (not merely Borel, but actually computable, and moreover functorial) from each to the corresponding , and also from each to (which proves more challenging than it was for the groups!). It remains open whether a theorem analogous to that of Hjorth-Thomas holds for the fields, but we use the notion of countable reductions to show that the fundamental obstacle to a reduction from to is the uncountability of these spaces. This is joint work with Meng-Che 'Turbo' Ho and Julia Knight.

Next Week in Logic at CUNY:

- - - - Monday, Nov 18, 2024 - - - -

Rutgers Logic Seminar
Monday November 18, 3:30pm, Rutgers University, Hill Center, Hill 705

Brent Cody, VCU
Two-cardinal derived topologies

Logic and Metaphysics Workshop
Date: Monday, November 18, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Claudio Calosi (Venice) and Damiano Costa (Lugano).
Title: Pluralisms in gunky worlds

Abstract: The possibility of gunk, namely the possibility that an entity possesses an infinitely descending chain of smaller and smaller parts, has famously been used by Schaffer (2010) to argue in favour of priority monism, namely the view that the whole universe is the fundamental concrete entity on which any of its parts depends. In this paper, we present and explore different principled ways of being a priority pluralist in gunky worlds, thus deflecting the gunk argument. Some of these ways turn out to be examples of middleism, i.e. the view that the fundamental level is that of middle-sized and mereologically intermediate objects. Hence, they don’t only effectively deflect the gunk threat to pluralism, but they also catalyse any argument in favour of the middleist position.

- - - - Tuesday, Nov 19, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, November 19, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Bartosz Wcisło, University of Gdańsk

- - - - Wednesday, Nov 20, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Arnon Avron, Tel-Aviv University.

Date and Time: Wednesday November 20, 2024, 7:00 - 8:30 PM. IN-PERSON TALK

Title: What is the Structure of the Natural numbers?

Abstract: We present some theorems that show that the notion of a structure, which is central for both Structuralism and category theory, has the very serious defect of having no satisfactory notion of identity which can be associated with it. We use those theorems to show that in particular, there are at least two completely different structures that are entitled to be taken as `the structure of the natural numbers', and any choice between them would arbitrarily favor one of them over the equally legitimate other. This fact refutes (so we believe) the structuralist thesis that the natural numbers are just positions (or places) in "the structure of the natural numbers". Finally, we argue for the high plausibility of the identification of the natural numbers with the finite von Neumann ordinals.

- - - - Thursday, Nov 21, 2024 - - - -

- - - - Friday, Nov 22, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, November 22, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Alejandro Poveda, Harvard University

Logic Workshop
CUNY Graduate Center
Friday, November 22, 2:00pm-3:30pm, Room 4419

Alex Kruckman, Wesleyan 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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59th Nankai Logic Colloquium

Nankai Logic Colloquium

11/11/2024 1:26:38

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon. Our speaker this week will be Xu Wang from the Nankai University. This talk will take place this Friday, November 15th, from 4pm to 5pm (UTC+8, Beijing time).

Title: A hierarchy on non-archimedean CLI Polish groups

Abstract: We introduce a hierarchy on the class of non-archimedean Polish groups that admit a compatible complete left-invariant metric. We denote this hierarchy by α-CLI and L-α-CLI, where α is a countable ordinal. We establish three results: (1) G is 0-CLI iff G={1_G}; (2) G is 1-CLI iff G admits a compatible complete two-sided invariant metric; and (3) G is L-α-CLI iff G is locally α-CLI, i.e., G contains an open subgroup that is α-CLI. Next we prove this hierarchy is proper by constructing non-archimedean CLI Polish groups G_α and H_α for α<ω_1, such that (1) H_α is α-CLI but not L-β-CLI for β<α; and (2) G_α is (α+1)-CLI but not L-α-CLI. This is a joint work with Longyun Ding.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 59th Nankai Logic Colloquium-- Xu Wang Time: 16:00pm, Nov. 15, 2024(Beijing Time) Zoom Number: 436 658 8683 Passcode: 477893 Link: https://frontai-hk.zoom.us/j/4366588683?pwd=ob0TsLuLeIl0JT7403RaqvFKgOnuRf.1&omn=86381415451

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Logic Seminar 13.11.2024 at 17:00 hrs at NUS by Dilip Raghavan

NUS Logic Seminar

11/11/2024 5:47:40

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 13 November 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Dilip Raghavan Title: Nowhere dense ultrafilters and weak forms of selectivity Abstract: I will present some recent consistency results on nowhere dense ultrafilters and a weakening of selectivity. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Set theory and topology seminar 12.11.2024 Marcin Michalski

Wrocław Set Theory Seminar

11/11/2024 12:45:33

I am happy to announce that at the seminar in set theory and topology on 2024-11-12 Tuesday 17:15 in MI, 605 the lecture:

On algebraic sums, trees and ideals in the Cantor space

will be presented by

Marcin Michalski

Abstract: We work in the Cantor space $2^\omega$ equipped with the standard coordinate-wise addition $+$. We will discuss the results adhering to the following pattern. Let $\mathcal{I}\in \{\mathcal{M}, \mathcal{N}, \mathcal{M}\cap \mathcal{N}, \mathcal{E}\}$ and $T$ be a perfect, uniformly perfect or Silver tree. Then for every $A\in \mathcal{I} $ there exists $T'\subseteq T$ of the same kind as $T$ such that \[A+\underbrace{[T']+[T']+\dots +[T']}_{n-times}\in \mathcal{I}\] for each $n\in\omega$.
We also prove weaker statements for splitting trees. For the case $\mathcal{E}$ we also provide a simple characterization of the basis of $\mathcal{E}$.
Lastly, we will briefly mention the challenges of translating these kind of results to the Baire space $\mathbb{Z}^\omega$.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You,
on behalf of all the organizers,
Szymon Żeberski

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

***

Our webpages:
https://prac.im.pwr.edu.pl/~settheory
https://settheory.pwr.edu.pl/ (legacy page)
http://www.math.uni.wroc.pl/seminarium/topologia

Set theory and topology seminar 19.11.2024 Takheiko Gappo (TU Wien)

Wrocław Set Theory Seminar

11/14/2024 1:22:37

I am happy to announce that at the seminar in set theory and topology on 2024-11-19 Tuesday 17:15 in Mathematical Institute, University of Wroclaw, 605 the lecture:

Maximality, Recurrence, Ground

will be presented by

Takehiko Gappo

Abstract: The Maximality Principle (introduced by Hamkins) asserts that any forceably necessary statement is true. The Recurrence Axiom (introduced by Fuchino and Usuba) asserts that any forceable statement is true in some ground, where an inner model W is said to be a ground if VV is a set-sized forcing extension of W. In this talk, we will explore natural variants of these principles by restricting the complexity of statements, allowing parameters, and varying the class of forcing posets. For example, we discuss the (in)compatibility of these variants with the Ground Axiom (introduced by Hamkins and Reitz), which asserts that there are no non-trivial grounds. This talk is based on joint work with Sakaé Fuchino and Francesco Parente.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You,
on behalf of all the organizers,
PBN

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

***

Our webpages:
https://prac.im.pwr.edu.pl/~settheory
https://settheory.pwr.edu.pl/ (legacy page)
http://www.math.uni.wroc.pl/seminarium/topologia

KGRC Set Theory talks November 21

Kurt Godel Research Center

11/15/2024 4:23:26

KGRC/Institute of Mathematics invites you to the following talks: updates at https://kgrc.univie.ac.at/eventsnews/ Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, November 21, 11:30am--1:00pm, hybrid mode "Turing-invariant functions under determinacy II" B. Siskind (TU Wien) This talk is part of a two-part series. In part 1, we discussed some results about Turing-invariant functions from reals into $\omega_1$ under the Axiom of Determinacy. Today in part 2, we'll see how these results can be used to prove Martin's Conjecture for order-preserving functions up to the double hyperjump (and some other related things, time permitting). Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, November 21, 3:00pm--3:50pm, hybrid mode "Definable hypergraphs and the Wadge hierarchy" P. Schlicht (U Siena, IT) The open graph dichotomy states that the complete graph on the Cantor space is least among open graphs on analytic sets with respect to the ordering given by continuous graph homomorphisms. Ben Miller used dichotomies of this form to prove many interesting theorems in descriptive set theory. I will survey some applications to the descriptive set theory of generalised Cantor spaces. I will further draw a connection to the Wadge hierarchy of generalised Cantor spaces and sketch what is currently known about its structure. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recording available so far of the Set Theory Seminar: Nov 14: B. Siskind (TU Wien), "Turing-invariant functions under determinacy I". https://ucloud.univie.ac.at/index.php/s/7Mqbmb8zoFp6zmC -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

11/17/2024 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Nov 18, 2024 - - - -

Rutgers Logic Seminar
Monday November 18, 3:30pm, Rutgers University, Hill Center, Hill 705

Brent Cody, VCU
Two-cardinal derived topologies

Logic and Metaphysics Workshop
Date: Monday, November 18, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Claudio Calosi (Venice) and Damiano Costa (Lugano).
Title: Pluralisms in gunky worlds

Abstract: The possibility of gunk, namely the possibility that an entity possesses an infinitely descending chain of smaller and smaller parts, has famously been used by Schaffer (2010) to argue in favour of priority monism, namely the view that the whole universe is the fundamental concrete entity on which any of its parts depends. In this paper, we present and explore different principled ways of being a priority pluralist in gunky worlds, thus deflecting the gunk argument. Some of these ways turn out to be examples of middleism, i.e. the view that the fundamental level is that of middle-sized and mereologically intermediate objects. Hence, they don’t only effectively deflect the gunk threat to pluralism, but they also catalyse any argument in favour of the middleist position.

- - - - Tuesday, Nov 19, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, November 19, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Bartosz Wcisło, University of Gdańsk

Saturation properties for propositionally sound satisfaction classes

Over the last years, a lot of progress has been achieved in understanding the arithmetical strength of axiomatic theories of compositional truth. It turned out that a theory $C T -$ of compositional truth for arithmetical sentences can become non-conservative over $P A$ upon adding some seemingly benign principles.

One of the principles whose arithmetical strength is still unknown is the axiom of propositional soundness which says that for any arithmetical sentence $ϕ$ which is a propositional tautology, $ϕ$ is true in the sense of the truth predicate. It is an open problem whether this axiom together with $C T -$ is conservative over $P A$ .

In our talk, we will show that if $(M, T)$ is a model of $C T -$ satisfying the propositional soundness principle, then $(M, T)$ satisfies a certain amount of saturation: if $(ϕ i) i < c$ is a sequence of sentences such that for any standard $i$ , $ϕ i$ is true in the sense of the truth predicate, then there is a nonstandard $d$ such that for each $i \in [0, d]$ , $ϕ i$ is true. This puts very strong limitations on any possible conservativeness proof. The result may be seen as a counterpart to the classical theorem of Lachlan which says that the arithmetical part of any model of $C T -$ is recursively saturated.

- - - - Wednesday, Nov 20, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Arnon Avron, Tel-Aviv University.

Date and Time: Wednesday November 20, 2024, 7:00 - 8:30 PM. IN-PERSON TALK

Title: What is the Structure of the Natural numbers?

Abstract: We present some theorems that show that the notion of a structure, which is central for both Structuralism and category theory, has the very serious defect of having no satisfactory notion of identity which can be associated with it. We use those theorems to show that in particular, there are at least two completely different structures that are entitled to be taken as `the structure of the natural numbers', and any choice between them would arbitrarily favor one of them over the equally legitimate other. This fact refutes (so we believe) the structuralist thesis that the natural numbers are just positions (or places) in "the structure of the natural numbers". Finally, we argue for the high plausibility of the identification of the natural numbers with the finite von Neumann ordinals.

- - - - Thursday, Nov 21, 2024 - - - -

- - - - Friday, Nov 22, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, November 22, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Alejandro Poveda, Harvard University
Identity crises phenomena between the first supercompact cardinal and Vopěnka's Principle

We will report on some recent results on the large cardinal hierarchy between the first supercompact cardinal and Vopěnka's Principle. We present various consistency results as well as a conjecture as for how the large-cardinal hierarchy of $Ultimate$ - $L$ looks like at these latitudes. The main result will be the consistency with very large cardinals of a new Kimchi-Magidor configuration; namely, we will present a model where every supercompact cardinal is supercompact with inaccessible target points. This answers a question of Bagaria and Magidor. This configuration is a consequence of a new axiom (named $A$ ) which regards the mutual relationship between superstrong and tall cardinals. Time permitting we shall discuss the interplay between $A$ and $Ultimate$ - $L$ and propose a few open questions.

Logic Workshop
CUNY Graduate Center
Friday, November 22, 2:00pm-3:30pm, Room 4419

Alex Kruckman, Wesleyan University

The complexity of ages admitting a universal limit structure

An age is a hereditary class of finitely generated structures with the joint embedding property which is countable up to isomorphism. If $K$ is an age, a $K$ -limit is a countable structure $M$ such that every finitely generated substructure of $M$ is in $K$ . A $K$ -limit $U$ is universal if every $K$ -limit embeds in $U$ . It is well-known that $K$ has the amalgamation property (AP) if and only if $K$ admits a homogeneous limit (the Fraïssé limit), which is always universal. But not every age with a universal limit has AP. We show that, while the existence of a universal limit can be characterized by the well-definedness of a certain ordinal-valued rank on structures in $K$ , it is not equivalent to any finitary diagrammatic property like AP. More precisely, we show that for ages in a fixed sufficiently rich language $L$ , the property of admitting a universal limit is complete coanalytic. This is joint work with Aristotelis Panagiotopoulos.

Next Week in Logic at CUNY:

- - - - Monday, Nov 25, 2024 - - - -

Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705

Koichi Oyakawa, Vanderbilt

Logic and Metaphysics Workshop
Date: Monday, November 25, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Damian Szmuc (Buenos Aires).
Title: More semantics for Angell’s logic of Analytic Containment

Abstract: This presentation aims to explore new semantics for Angell’s logic of Analytic Containment through the discussion of the topic-transformativeness of negation. For this purpose, we review some new developments by Song, Omori, Arenhart, and Tojo on two-address valuations for topic-transparent logics related to content inclusion, and extend their techniques for Angell’s logic of Analytic Containment. In particular, we present a 4-valued non-deterministic and a 16-valued deterministic semantics, both obtained through direct products of De Morgan lattices and involutive semilattices.

- - - - Tuesday, Nov 26, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, November 26, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Zachiri Mckenzie, University of Chester

- - - - Wednesday, Nov 27, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Tim Hosgood

Date and Time: Wednesday November 27, 2024, 7:00 - 8:30 PM.

Title: TBA.

- - - - Thursday, Nov 28, 2024 - - - -

*** GRADUATE CENTER CLOSED ***

- - - - Friday, Nov 29, 2024 - - - -

*** GRADUATE CENTER NO CLASSES SCHEDULED ***

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Wednesday seminar

Prague Set Theory Seminar

11/17/2024 22:35:51

Dear all, The seminar meets on Wednesday November 20th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program has not been decided yet, walk-in speakers will be welcome. In case nobody would be interested to speak, Chris agreed to give an ad hoc talk on 'Connections between derived limits and various topics from set theory to be chosen according to the interests of the audience. Possible topics include but are not limited to: guessing models, the open coloring axiom, the P-ideal dichotomy, square sequences, and cardinal characteristics.' Best, David

60th Nankai Logic Colloquium

Nankai Logic Colloquium

11/18/2024 0:44:55

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Antoine Poulin from McGill University. This talk will take place this Friday, November 22rd, from 9am to 10am (UTC+8, Beijing time).

Title: Measure equivalence of Baumslag-Solitar groups and type III relations

Abstract: In this talk, we present the classification of Baumslag-Solitar groups up to measure equivalence and explore the techniques crucial to the proof. We present basic theory and invariants of measure class preserving countable Borel equivalence relations of type III, i.e not preserving any equivalent measure. Based on work joint with D. Gaboriau, A. Tserunyan, R. Tucker-Drob and K. Wróbel.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 60th Nankai Logic Colloquium-- Antoine Poulin Time: 9:00am, Nov. 22, 2024(Beijing Time) Zoom Number: 436 658 8683 Passcode: 477893 Link: https://frontai-hk.zoom.us/j/4366588683?pwd=ob0TsLuLeIl0JT7403RaqvFKgOnuRf.1&omn=82194843712

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

KGRC Set Theory talks November 26--November 28

Kurt Godel Research Center

11/22/2024 8:28:11

KGRC/Institute of Mathematics invites you to the following talks: updates at https://kgrc.univie.ac.at/eventsnews/ Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, TUESDAY, November 26, 3:00pm--4:30pm, hybrid mode "Cichoń's maximum with evasion number" T. Yamazoe (Kobe U, JP) We show that the evasion number $\mathfrak{e}$ can be added to Cichoń's maximum with a distinct value. More specifically, it is consistent that $\aleph_1<\operatorname{add}(\mathcal{N})<\operatorname{cov}(\mathcal{N})<\mathfrak{b}<\mathfrak{e}<\operatorname{non}(\mathcal{M})<\operatorname{cov}(\mathcal{M})<\mathfrak{d}<\operatorname{non}(\mathcal{N})<\operatorname{cof}(\mathcal{N})<2^{\aleph_0}$ holds. This talk is related to the speaker's upcoming talk at the Algebra seminar in TU Wien. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, November 28, 11:30am--1:00pm, hybrid mode "End spaces of Borel and measure-class-preserving graphs" R. Chen (U of Michigan, Detroit, US) An important aspect of Borel dynamics and graph combinatorics concerns the large-scale topological and geometric structure of Borel trees and graphs, as made precise by the notion of an end ("connected component at infinity") of a graph. For instance, by a result of Gaboriau and Ghys, a probability-measure-preserving graph with at least 3 ends per component must be non-amenable almost everywhere; the proof of this result uses a Borel version of Stallings' theorem on ends of groups. We will give a survey of some recent results in this area, that all share a theme of "doing Borel topology" on spaces of ends of graphs. This talk is based on joint works with Antoine Poulin, Ran Tao, Greg Terlov, Anush Tserunyan, and Robin Tucker-Drob. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, November 28, 3:00pm--3:50pm, hybrid mode "Structurable equivalence relations, Borel combinatorics, and countable model theory" R. Chen (U of Michigan, Detroit, US) The theory of countable Borel equivalence relations (CBERs) provides a global framework for discussing and comparing all locally countable Borel combinatorics problems (graph colorings, group actions, etc.) at once. We present a result showing that in a precise sense, all such combinatorial problems on CBERs can be reduced to syntactic definability problems in the infinitary logic $L_{\omega_1\omega}$ on countable structures. This provides a rigorous explanation of a well-known heuristic in Borel combinatorics, that many arguments amount to "doing countable combinatorics in a uniformly Borel way", while also allowing finer distinctions to be made between different classically equivalent combinatorial problems. This talk is based on joint works with Alexander Kechris and Rishi Banerjee. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recording available so far of the Set Theory Seminar: Nov 14: B. Siskind (TU Wien), "Turing-invariant functions under determinacy II". https://ucloud.univie.ac.at/index.php/s/DmME2JeAXERAKZk Video recording available so far of the Logic Colloquium: Nov 21: P. Schlicht (U Siena, IT). "Definable hypergraphs and the Wadge hierarchy". https://ucloud.univie.ac.at/index.php/s/6yDzHAbHA3waxsX -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

Set theory and topology seminar 26.11.2024 Łukasz Mazurkiewicz

Wrocław Set Theory Seminar

11/24/2024 14:15:42

I am happy to announce that at the seminar in set theory and topology on 2024-11-26 Tuesday 17:15 in MI, 605 the lecture:

On algebraic sums, trees and ideals in the Baire space

will be presented by

Łukasz Mazurkiewicz

Abstract: The talk is a follow-up to Marcin Michalski talk from 12.11.2024. Marcin talked about results regarding algebraic sums of bodies of trees and sets from classical $\sigma$-ideals in the Cantor space, especially $\sigma$-ideal of meager sets. This time we will talk about migrating these results to the context of the Baire space, with emphasis on $\sigma$-ideal of "null" sets (whatever that means in the Baire space).

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You,
on behalf of all the organizers,
Szymon Żeberski

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

***

Our webpages:
https://prac.im.pwr.edu.pl/~settheory
https://settheory.pwr.edu.pl/ (legacy page)
http://www.math.uni.wroc.pl/seminarium/topologia

This Week in Logic at CUNY

11/24/2024 22:37:00

This Week in Logic at CUNY:

- - - - Monday, Nov 25, 2024 - - - -

Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705

Koichi Oyakawa, Vanderbilt

Logic and Metaphysics Workshop
Date: Monday, November 25, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Damian Szmuc (Buenos Aires).
Title: More semantics for Angell’s logic of Analytic Containment

Abstract: This presentation aims to explore new semantics for Angell’s logic of Analytic Containment through the discussion of the topic-transformativeness of negation. For this purpose, we review some new developments by Song, Omori, Arenhart, and Tojo on two-address valuations for topic-transparent logics related to content inclusion, and extend their techniques for Angell’s logic of Analytic Containment. In particular, we present a 4-valued non-deterministic and a 16-valued deterministic semantics, both obtained through direct products of De Morgan lattices and involutive semilattices.

- - - - Tuesday, Nov 26, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, November 26, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Zachiri Mckenzie, University of Chester

Well-founded models of fragments of Collection

Let be the weak set theory (with powersets) axiomatised by: , , , , , transitive containment (), and . In this talk I will discuss the relationship between two alternative versions of the set-theoretic collection scheme: Collection and Strong Collection. Both of these schemes yield when added to , but when restricted the -formulae (denoted and ) these alternative versions of set-theoretic collection differ. In particular, over the theory , is equivalent to . And, proves the consistency of . In this talk I will show that, despite this difference in consistency strength, every countable well-founded model of satisfies . If time permits I will outline how this argument can be refined to show that proves .

- - - - Wednesday, Nov 27, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Tim Hosgood

Date and Time: Wednesday November 27, 2024, 7:00 - 8:30 PM.

Title: TBA.

- - - - Thursday, Nov 28, 2024 - - - -

*** GRADUATE CENTER CLOSED ***

- - - - Friday, Nov 29, 2024 - - - -

*** GRADUATE CENTER NO CLASSES SCHEDULED ***

Next Week in Logic at CUNY:

- - - - Monday, Dec 2, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, December 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Sam Burns (Columbia).
Title: Formalizability and mathematical rigor

Abstract: Mathematicians do not generally prove theorems via formal derivations. Given that formal derivations are the contemporary ideal of mathematical rigor, this raises questions as to how informal proofs can be rigorous. Responding to this worry, derivationists claim that an informal proof is rigorous if it can be routinely translated into a formal derivation. In this talk I raise some concerns about derivationism as a universal claim about mathematical rigor. I break the derivationist thesis into two parts: a claim about the formalizability of the theorems themselves, and a claim about the formalizability of mathematical inferences. I then discuss some case studies that call into question the plausibility of each part of the derivationist thesis. Based on these case studies, I suggest that a contextualist account of mathematical rigor best coheres with mathematical practice, thereby rejecting the claim that (complete) formalizability is a desideratum in all mathematical contexts.

- - - - Tuesday, Dec 3, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, December 3, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Mateusz Łełyk, University of Warsaw

- - - - Wednesday, Dec 4, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Charlotte Aten, University of Colorado, Boulder.

Date and Time: Wednesday December 4, 2024, 7:00 - 8:30 PM. ZOOM TALK

Title: Invariants of structures.

Abstract: I will discuss one part of my PhD thesis, in which I provide a categorification of the notion of a mathematical structure originally given by Bourbaki in their set theory textbook. The main result is that any isomorphism-invariant property of a finite structure can be checked by computing the number of isomorphic copies of small substructures it contains. A special case of this theorem is the classical result of Hilbert about elementary symmetric polynomials generating the algebra of all symmetric polynomials. I will also discuss how the logical complexity of a positive formula controls the size of the small substructures one must count.

- - - - Thursday, Dec 5, 2024 - - - -

- - - - Friday, Dec 6, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday, December 6, 2:00pm-3:30pm, Room 4419

Roman Kossak, CUNY
Lattices of elementary submodels of recursively saturated models of PA

Much work on elementary submodels of recursively saturated models of PA was done, beginning in the 1980s, by Craig Smoryński, Richard Kaye, Henryk Kotlarski, Jim Schmerl, and myself. The set of all elementary substructures of a recursively saturated model ordered by inclusion forms a lattice . Kotlarski asked whether depends on . In the talk, I will describe the architecture of , and I will survey what is known and what is still open about Kotlarski's question.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

61st Nankai Logic Colloquium

Nankai Logic Colloquium

11/25/2024 0:06:44

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon. Our speaker this week will be Feng Li from Nankai University. This talk will take place this Friday, November 29th, from 4pm to 5pm (UTC+8, Beijing time).

Title: Extremely amenable automorphism groups of countable structures

Abstract: Extreme amenability is a remarkable property for a topological group to have. Ever since the first example of such groups was constructed in 1975, many groups have been shown to be extremely amenable. In this talk I will address the question: How many pairwise non-isomorphic extremely amenable groups are there? We demonstrate that there are continuum many pairwise non-isomorphic extremely amenable groups which are automorphism groups of countable structures, and in particular Polish. I will also talk about some related results from the point of view of descriptive set theory. This is joint work with Mahmood Etedadialiabadi and Su Gao.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 61st Nankai Logic Colloquium-- Feng Li Time: 16:00pm, Nov. 29, 2024(Beijing Time) Zoom Number: 436 658 8683 Passcode: 477893 Link: https://frontai-hk.zoom.us/j/4366588683?pwd=ob0TsLuLeIl0JT7403RaqvFKgOnuRf.1&omn=83397983387

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Logic Seminar 26/11/2024 14:00 hrs by Patrick Lutz at NUS - Note the time and place

NUS Logic Seminar

11/25/2024 1:19:52

Invitation to the Logic Seminar at the National University of Singapore Date: Tuesday 26 November 2024, 14:00 hrs Place: NUS, Faculty of Science, Room S16#05-18 Speaker: Patrick Lutz Title: Complexity of oracles for packing dimension Abstract: Recently, there has been a spate of work applying tools from computability theory to prove theorems about Hausdorff dimension and packing dimension. Central to these applications are computability-theoretic analogues of Hausdorff dimension and packing dimension, known respectively as effective Hausdorff dimension and effective packing dimension. A fact which is useful for many applications is that for sufficiently simple sets in particular, for Pi-0-1 sets the Hausdorff dimension and effective Hausdorff dimension agree. Unfortunately, the corresponding statement for packing dimension is known to fail. In particular, an example due to Conidis shows that there is a Pi-0-1 set of packing dimension 0 and effective packing dimension 1. In this talk, I will consider the question of exactly how bad this failure is. In particular, given a Pi-0-1 set E, what is the minimum complexity of an oracle A for which the packing dimension of E is equal to the effective packing dimension of E relative to A? Surprisingly, it turns out that there is not always even a hyperarithmetic oracle. I will also discuss to what extent this affects potential applications of effective packing dimension. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar

11/26/2024 13:00:52

Dear all, There is no seminar tomorrow Wednesday November 27th. The seminar will meet again next week, Wednesday December 4th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is TBD, the backup option is me giving a talk on some topic. (I will send an update in case there is a specific talk to announce.) Best, David

KGRC talks December 5

Kurt Godel Research Center

11/29/2024 6:11:39

KGRC/Institute of Mathematics invites you to the following talks: updates at https://kgrc.univie.ac.at/eventsnews/ Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, December 5, 11:30am--1:00pm, hybrid mode "Labelled sets" P. Marun (Czech Academy of Sciences, Prague, CZ) A theorem of Dilworth asserts that, if a poset $P$ has no antichains whose size is larger than $m$, where $m$ is a natural number, then $P$ can be written as a union of $m$ many chains. If $m$ is instead an infinite cardinal, then the analogous statement is false, counterexamples were constructed by Perles. In recent work, Abraham and Pouzet gave a basis for the class of such counterexamples, and asked if it could be somewhat simplified. Labelled sets arise in connection with these counterexamples. We show that, when the underlying sets are $\aleph_1$-dense, then any two labelled sets embed into each other. Zoom info: if you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, December 5, 3:00pm--3:50pm, hybrid mode "Basis for Uncountable Linear Orders" W. Chan (TU Wien) This talk will discuss finite basis results for classes of uncountable linear orderings of size above familiar cardinalities under order embeddings. Zoom info: if you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recordings available so far of the Set Theory Seminar: Nov 26: T. Yamazoe (Kobe U, JP), "Cichoń's maximum with evasion number". https://ucloud.univie.ac.at/index.php/s/HwRDSdL7omKrj8s Nov 28: R. Chen (U of Michigan, Detroit, US), "End spaces of Borel and measure-class-preserving graphs". https://ucloud.univie.ac.at/index.php/s/JEbYCHmG4fKcK6B Slides available so far of the Logic Colloquium: Nov 28: R. Chen (U of Michigan, Detroit, US), "Structurable equivalence relations, Borel combinatorics, and countable model theory". https://kgrc.univie.ac.at/fileadmin/user_upload/p_kgrc/Dokumente/2024/slides_Ronnie_Chen.pdf -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

Set theory and topology seminar 3.02.2024 Aleksander Cieślak

Wrocław Set Theory Seminar

11/29/2024 6:28:38

I am happy to announce that at the seminar in set theory and topology on 2024-12-03 Tuesday 17:15 in MI, 605 the lecture:

Distributivity and antichain number of algebra Borel modulo closed measure zero sets

will be presented by

Aleksander Cieślak

Abstract: We will investigate $\sigma$-ideals on polish spaces generated by closed sets and the two related cardinal invariants. To do so we will analyse the construction of Hurewicz schema from the theorem of Solecki saying that if J is generated by closed sets then every J-positive analytic set contains a J-positive $G_\delta$ set.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You,
on behalf of all the organizers,
Szymon Żeberski

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

***

Our webpages:
https://prac.im.pwr.edu.pl/~settheory
https://settheory.pwr.edu.pl/ (legacy page)
http://www.math.uni.wroc.pl/seminarium/topologia

This Week in Logic at CUNY

12/1/2024 22:37:00

This Week in Logic at CUNY:

- - - - Monday, Dec 2, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, December 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Sam Burns (Columbia).
Title: Formalizability and mathematical rigor

Abstract: Mathematicians do not generally prove theorems via formal derivations. Given that formal derivations are the contemporary ideal of mathematical rigor, this raises questions as to how informal proofs can be rigorous. Responding to this worry, derivationists claim that an informal proof is rigorous if it can be routinely translated into a formal derivation. In this talk I raise some concerns about derivationism as a universal claim about mathematical rigor. I break the derivationist thesis into two parts: a claim about the formalizability of the theorems themselves, and a claim about the formalizability of mathematical inferences. I then discuss some case studies that call into question the plausibility of each part of the derivationist thesis. Based on these case studies, I suggest that a contextualist account of mathematical rigor best coheres with mathematical practice, thereby rejecting the claim that (complete) formalizability is a desideratum in all mathematical contexts.

- - - - Tuesday, Dec 3, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, December 3, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Mateusz Łełyk, University of Warsaw

Varieties of truth definitions

In the talk we address the following problem: how many essentially different truth definitions (for the language of arithmetic) are there? Formally, a truth definition for us is just a sentence in some language , which extends the elementary arithmetic (a.k.a. ) and such that for some -formula ,for every sentence in the language of arithmetic. In other words is a sentence which can define a truth predicate for arithmetic (via a formula ). We investigate the structure of the definability relation between so defined truth definitions. To be more precise: we say that a truth definition (in a language ) defines a truth definition (in a language ) if and only if there are -formulae such that , where 's are all the non-arithmetical predicates from the language and denotes the result of translating by substituting for each occurrence of . We note that this translation does not relativize the quantifiers in and keeps the arithmetical symbols unchanged. Our main result is that the structure consisting of truth definitions which are conservative over the basic arithmetical theory forms a countable universal distributive lattice. Additionally, we (slightly) generalize the result of Pakhomov and Visser showing that the set of (Gödel codes of) definitions of truth is not -definable in the standard model of arithmetic.

This is joint work with Piotr Gruza which was published in here.

- - - - Wednesday, Dec 4, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Charlotte Aten, University of Colorado, Boulder.

Date and Time: Wednesday December 4, 2024, 7:00 - 8:30 PM. ZOOM TALK

Title: Invariants of structures.

Abstract: I will discuss one part of my PhD thesis, in which I provide a categorification of the notion of a mathematical structure originally given by Bourbaki in their set theory textbook. The main result is that any isomorphism-invariant property of a finite structure can be checked by computing the number of isomorphic copies of small substructures it contains. A special case of this theorem is the classical result of Hilbert about elementary symmetric polynomials generating the algebra of all symmetric polynomials. I will also discuss how the logical complexity of a positive formula controls the size of the small substructures one must count.

- - - - Thursday, Dec 5, 2024 - - - -

- - - - Friday, Dec 6, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday, December 6, 2:00pm-3:30pm, Room 4419

Roman Kossak, CUNY
Lattices of elementary submodels of recursively saturated models of PA

Much work on elementary submodels of recursively saturated models of PA was done, beginning in the 1980s, by Craig Smoryński, Richard Kaye, Henryk Kotlarski, Jim Schmerl, and myself. The set of all elementary substructures of a recursively saturated model ordered by inclusion forms a lattice . Kotlarski asked whether depends on . In the talk, I will describe the architecture of , and I will survey what is known and what is still open about Kotlarski's question.

Next Week in Logic at CUNY:

- - - - Monday, Dec 9, 2024 - - - -

Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705

Victoria Gitman, CUNY

Logic and Metaphysics Workshop
Date: Monday, December 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Justin Clarke-Doane (Columbia).
Title: Intuition and observation

Abstract: The motivating question of this talk is: ‘How are our beliefs in the theorems of mathematics justified?’ This is distinguished from the question ‘How are our mathematical beliefs reliably true?’ We examine an influential answer, outlined by Russell, championed by Gödel, and developed by those searching for new axioms to settle undecidables, that our mathematical beliefs are justified by ‘intuitions’, as our scientific beliefs are justified by observations. On this view, axioms are analogous to laws of nature. They are postulated to best systematize the data to be explained. We argue that there is a decisive difference between the cases. There is agreement on the data to be systematized in the scientific case that has no analog in the mathematical one. There is virtual consensus over observations, but conspicuous dispute over intuitions. In this respect, mathematics more closely resembles philosophy. We conclude by distinguishing two ideas that have long been associated — realism (the idea that there is an independent reality) and objectivity (the idea that in a disagreement, only one of us can be right). We argue that, while realism is true of mathematics and philosophy, these domains fail to be objective. One upshot of the discussion is that even questions of fundamental physics may fail to be objective insofar as the mathematical, logical, and evaluative hypotheses that they presuppose fail to be. Another is pragmatism. Factual questions in mathematics, modality, logic, and evaluative areas go proxy for non-factual practical ones.

Note: This is joint work with Avner Ash (Boston College).

- - - - Tuesday, Dec 10, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, December 3, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Leszek Kołodziejczyk University of Warsaw

- - - - Wednesday, Dec 11, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Matthew Cushman, CUNY.

Date and Time: Wednesday December 11, 2024, 7:00 - 8:30 PM. IN PERSON TALK

Title: Recollements: gluing and fracture for categories.

Abstract: Recollements provide a way of gluing two categories together along a left-exact functor, or conversely of obtaining a semi-orthogonal decomposition of a category by two full subcategories. Every recollement comes with a fracture square, which in some circumstances can be extended to a hexagon-shaped diagram of fiber sequences. In this talk we will discuss concrete examples from topological spaces and graphs before moving to smooth manifolds and the recollement that gives rise to differential cohomology theories.

- - - - Thursday, Dec 12, 2024 - - - -

- - - - Friday, Dec 13, 2024 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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62nd Nankai Logic Colloquium

Nankai Logic Colloquium

12/2/2024 1:11:24

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Anton Bernshteyn from the University of California, Los Angeles. This talk will take place this Friday, December 6th, from 9am to 10am (UTC+8, Beijing time).

Title: Borel Local Lemma for graphs of slow growth

Abstract: The Lovász Local Lemma is an important tool in probabilistic combinatorics. Roughly speaking, it shows the existence of a function satisfying certain combinatorial constraints by checking a set of numerical conditions. In addition to its importance in combinatorics, the Local Lemma has recently found applications in many other fields, such as ergodic theory. In this talk, we address the following question: When can we choose the function whose existence is guaranteed by the Local Lemma to be Borel? Csóka, Grabowski, Máthé, Pikhurko, and Tyros proved a Borel version of the Local Lemma under the assumption that a certain auxiliary graph is of subexponential growth. Unfortunately, their proof only works when the range of the desired function finite. Using a different approach, we extend their result to the case of continuous range as well as to graphs of limited exponential growth. This is joint work with Jing Yu.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 62nd Nankai Logic Colloquium-- Anton Bernshteyn

Time: 9:00am, Dec. 6, 2024(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=96276467164

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY

12/2/2024 9:34:56

Hi everyone,

Please note the following correction - the talk by Leszek Kołodziejczyk in the Models of Peano Arithmetic seminar will take place on December 10th.

All best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Dec 2, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, December 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Sam Burns (Columbia).
Title: Formalizability and mathematical rigor

Abstract: Mathematicians do not generally prove theorems via formal derivations. Given that formal derivations are the contemporary ideal of mathematical rigor, this raises questions as to how informal proofs can be rigorous. Responding to this worry, derivationists claim that an informal proof is rigorous if it can be routinely translated into a formal derivation. In this talk I raise some concerns about derivationism as a universal claim about mathematical rigor. I break the derivationist thesis into two parts: a claim about the formalizability of the theorems themselves, and a claim about the formalizability of mathematical inferences. I then discuss some case studies that call into question the plausibility of each part of the derivationist thesis. Based on these case studies, I suggest that a contextualist account of mathematical rigor best coheres with mathematical practice, thereby rejecting the claim that (complete) formalizability is a desideratum in all mathematical contexts.

- - - - Tuesday, Dec 3, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, December 3, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Mateusz Łełyk, University of Warsaw

Varieties of truth definitions

In the talk we address the following problem: how many essentially different truth definitions (for the language of arithmetic) are there? Formally, a truth definition for us is just a sentence in some language , which extends the elementary arithmetic (a.k.a. ) and such that for some -formula ,for every sentence in the language of arithmetic. In other words is a sentence which can define a truth predicate for arithmetic (via a formula ). We investigate the structure of the definability relation between so defined truth definitions. To be more precise: we say that a truth definition (in a language ) defines a truth definition (in a language ) if and only if there are -formulae such that , where 's are all the non-arithmetical predicates from the language and denotes the result of translating by substituting for each occurrence of . We note that this translation does not relativize the quantifiers in and keeps the arithmetical symbols unchanged. Our main result is that the structure consisting of truth definitions which are conservative over the basic arithmetical theory forms a countable universal distributive lattice. Additionally, we (slightly) generalize the result of Pakhomov and Visser showing that the set of (Gödel codes of) definitions of truth is not -definable in the standard model of arithmetic.

This is joint work with Piotr Gruza which was published in here.

- - - - Wednesday, Dec 4, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Charlotte Aten, University of Colorado, Boulder.

Date and Time: Wednesday December 4, 2024, 7:00 - 8:30 PM. ZOOM TALK

Title: Invariants of structures.

Abstract: I will discuss one part of my PhD thesis, in which I provide a categorification of the notion of a mathematical structure originally given by Bourbaki in their set theory textbook. The main result is that any isomorphism-invariant property of a finite structure can be checked by computing the number of isomorphic copies of small substructures it contains. A special case of this theorem is the classical result of Hilbert about elementary symmetric polynomials generating the algebra of all symmetric polynomials. I will also discuss how the logical complexity of a positive formula controls the size of the small substructures one must count.

- - - - Thursday, Dec 5, 2024 - - - -

- - - - Friday, Dec 6, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday, December 6, 2:00pm-3:30pm, Room 4419

Roman Kossak, CUNY
Lattices of elementary submodels of recursively saturated models of PA

Much work on elementary submodels of recursively saturated models of PA was done, beginning in the 1980s, by Craig Smoryński, Richard Kaye, Henryk Kotlarski, Jim Schmerl, and myself. The set of all elementary substructures of a recursively saturated model ordered by inclusion forms a lattice . Kotlarski asked whether depends on . In the talk, I will describe the architecture of , and I will survey what is known and what is still open about Kotlarski's question.

Next Week in Logic at CUNY:

- - - - Monday, Dec 9, 2024 - - - -

Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705

Victoria Gitman, CUNY

Logic and Metaphysics Workshop
Date: Monday, December 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Justin Clarke-Doane (Columbia).
Title: Intuition and observation

Abstract: The motivating question of this talk is: ‘How are our beliefs in the theorems of mathematics justified?’ This is distinguished from the question ‘How are our mathematical beliefs reliably true?’ We examine an influential answer, outlined by Russell, championed by Gödel, and developed by those searching for new axioms to settle undecidables, that our mathematical beliefs are justified by ‘intuitions’, as our scientific beliefs are justified by observations. On this view, axioms are analogous to laws of nature. They are postulated to best systematize the data to be explained. We argue that there is a decisive difference between the cases. There is agreement on the data to be systematized in the scientific case that has no analog in the mathematical one. There is virtual consensus over observations, but conspicuous dispute over intuitions. In this respect, mathematics more closely resembles philosophy. We conclude by distinguishing two ideas that have long been associated — realism (the idea that there is an independent reality) and objectivity (the idea that in a disagreement, only one of us can be right). We argue that, while realism is true of mathematics and philosophy, these domains fail to be objective. One upshot of the discussion is that even questions of fundamental physics may fail to be objective insofar as the mathematical, logical, and evaluative hypotheses that they presuppose fail to be. Another is pragmatism. Factual questions in mathematics, modality, logic, and evaluative areas go proxy for non-factual practical ones.

Note: This is joint work with Avner Ash (Boston College).

- - - - Tuesday, Dec 10, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, December 10, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Leszek Kołodziejczyk University of Warsaw

- - - - Wednesday, Dec 11, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Matthew Cushman, CUNY.

Date and Time: Wednesday December 11, 2024, 7:00 - 8:30 PM. IN PERSON TALK

Title: Recollements: gluing and fracture for categories.

Abstract: Recollements provide a way of gluing two categories together along a left-exact functor, or conversely of obtaining a semi-orthogonal decomposition of a category by two full subcategories. Every recollement comes with a fracture square, which in some circumstances can be extended to a hexagon-shaped diagram of fiber sequences. In this talk we will discuss concrete examples from topological spaces and graphs before moving to smooth manifolds and the recollement that gives rise to differential cohomology theories.

- - - - Thursday, Dec 12, 2024 - - - -

- - - - Friday, Dec 13, 2024 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Cross-Alps Logic Seminar (speaker: Mai Gehrke)

Cross-Alps Logic Seminar

12/3/2024 14:07:04

On Friday 06.12.2024 at 16.00 CET

Mai Gehrke (Université Côte d’Azur)

will give a talk on

Introduction to Stone, Priestley, and the Omega-Point dualities and some generalisations

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

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

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

All the best,
Vincenzo

Set theory and topology seminar 10.12.2024 Arturo Martinez Celis

Wrocław Set Theory Seminar

12/4/2024 6:11:26

I am happy to announce that at the seminar in set theory and topology on 2024-12-10 Tuesday 17:15 in MI, 605 the lecture:

Parametrized Diamonds

will be presented by

Arturo Martinez Celis

Abstract: In this talk we will discuss a plethora of diamond-like principles compatible with the negation of CH. We will discuss their consistency, how they relate to each other and we will see some applications.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You,
on behalf of all the organizers,
Szymon Żeberski

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

***

Our webpages:
https://prac.im.pwr.edu.pl/~settheory
https://settheory.pwr.edu.pl/ (legacy page)
http://www.math.uni.wroc.pl/seminarium/topologia

This Week in Logic at CUNY - FINAL(?) MAILING OF SEMESTER

This Week in Logic at CUNY

12/8/2024 22:30:00

Hi everyone,

It looks like most seminars are holding their final meetings of the semester this week. Unless additional talks are scheduled, this will be the last regular mailing of "This Week in Logic at CUNY" for the Fall 2024 semester. We will resume at the end of January, 2025. Have a peaceful and productive break!

Best to all in this holiday season,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Dec 9, 2024 - - - -

Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705

Victoria Gitman, CUNY

Upward Lowenheim-Skolem numbers for abstract logics

Logic and Metaphysics Workshop
Date: Monday, December 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Justin Clarke-Doane (Columbia).
Title: Intuition and observation

Abstract: The motivating question of this talk is: ‘How are our beliefs in the theorems of mathematics justified?’ This is distinguished from the question ‘How are our mathematical beliefs reliably true?’ We examine an influential answer, outlined by Russell, championed by Gödel, and developed by those searching for new axioms to settle undecidables, that our mathematical beliefs are justified by ‘intuitions’, as our scientific beliefs are justified by observations. On this view, axioms are analogous to laws of nature. They are postulated to best systematize the data to be explained. We argue that there is a decisive difference between the cases. There is agreement on the data to be systematized in the scientific case that has no analog in the mathematical one. There is virtual consensus over observations, but conspicuous dispute over intuitions. In this respect, mathematics more closely resembles philosophy. We conclude by distinguishing two ideas that have long been associated — realism (the idea that there is an independent reality) and objectivity (the idea that in a disagreement, only one of us can be right). We argue that, while realism is true of mathematics and philosophy, these domains fail to be objective. One upshot of the discussion is that even questions of fundamental physics may fail to be objective insofar as the mathematical, logical, and evaluative hypotheses that they presuppose fail to be. Another is pragmatism. Factual questions in mathematics, modality, logic, and evaluative areas go proxy for non-factual practical ones.

Note: This is joint work with Avner Ash (Boston College).

- - - - Tuesday, Dec 10, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, December 10, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Leszek Kołodziejczyk, University of Warsaw
Models of fragments of PA with low Scott rank

The infinitary logic $L ω 1, ω$ extends first-order logic by allowing countable disjunctions and conjunctions of formulas. Every countable structure can be described up to isomorphism (within the class of countable structures) by an $L ω 1, ω$ sentence. This gives rise to a particular way of measuring the complexity of countable structures: there is a natural alternation hierarchy $(Π in α : α < ω 1)$ of $L ω 1, ω$ formulas, and the Scott rank of a structure $A$ is the smallest ordinal $α$ such that $A$ can be described up to isomorphism by a $Π in α + 1$ sentence.

In recent years, beginning with a paper by Montalban and Rossegger, the Scott rank of models of arithmetic has attracted some attention. We now know, for instance, that every nonstandard pointwise definable model of $P A$ has Scott rank at least omega, that all other nonstandard models of $P A$ must have rank at least $ω + 1$ , and that recursively saturated models of $P A$ have rank exactly $ω + 1$ . This naturally leads one to ask about possible Scott ranks of models of subtheories of $P A$ . In particular: what is the lowest possible Scott rank of a structure satisfying $I Σ n + \neg B Σ n + 1$ ? What about $B Σ n + \neg I Σ n$ ?

We prove that every nonstandard model of $B Σ n$ must have Scott rank at least $n + 1$ . Moreover, this lower bound is tight: it is realized both by the most familiar models of $I Σ n + \neg B Σ n + 1$ , namely pointwise $Σ n + 1$ -definable substructures of models of $I Σ n + 1$ , and by the most familiar models of $B Σ n + \neg I Σ n$ , namely initial segments generated by the $Σ n$ -definables of models of $I Σ n$ . Time permitting, we also hope to mention a few other facts about Scott ranks of models of fragments of $P A$ .

This is joint work in progress with Mateusz Łełyk and Patryk Szlufik.

- - - - Wednesday, Dec 11, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Matthew Cushman, CUNY.

Date and Time: Wednesday December 11, 2024, 7:00 - 8:30 PM. IN PERSON TALK

Title: Recollements: gluing and fracture for categories.

Abstract: Recollements provide a way of gluing two categories together along a left-exact functor, or conversely of obtaining a semi-orthogonal decomposition of a category by two full subcategories. Every recollement comes with a fracture square, which in some circumstances can be extended to a hexagon-shaped diagram of fiber sequences. In this talk we will discuss concrete examples from topological spaces and graphs before moving to smooth manifolds and the recollement that gives rise to differential cohomology theories.

- - - - Thursday, Dec 12, 2024 - - - -

- - - - Friday, Dec 13, 2024 - - - -

Next Week in Logic at CUNY:

- - - - Monday, Dec 16, 2024 - - - -

- - - - Tuesday, Dec 17, 2024 - - - -

- - - - Wednesday, Dec 18, 2024 - - - -

- - - - Thursday, Dec 19, 2024 - - - -

- - - - Friday, Dec 20, 2024 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

63rd Nankai Logic Colloquium

Nankai Logic Colloquium

12/9/2024 0:43:40

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Felix Weilacher from the University of California, Berkeley. This talk will take place this Friday, December 13th, from 9am to 10am (UTC+8, Beijing time).

Title: Separating complexity classes of LCL problems on grids

Abstract: We study the complexity of locally checkable labeling (LCL) problems on Z^n from the point of view of descriptive set theory, computability theory, and factors of i.i.d. Our results separate various complexity classes that were not previously known to be distinct and serve as counterexamples to a number of natural conjectures in the field.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 63rd Nankai Logic Colloquium-- Felix Weilacher Time: 9:00am, Dec. 13, 2024(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=94775493407

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Wednesday seminar

Prague Set Theory Seminar

12/9/2024 4:57:25

Dear all, The seminar meets on Wednesday December 11th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Noé de Rancourt -- Oscillation stability of l_\infty I will present the proof, obtained in a common work with Tristan Bice, Jan Hubička, and Matěj Konečný, of the oscillation stability of the Banach space l_\infty of bounded real sequences: every sufficiently definable Lipschitz real function defined on its unit sphere is almost constant on a suitably chosen linear isometric subcopy of l_\infty. Don't be afraid, behind this spooky analysis disguise, the proof is actually 90% combinatorics (it is based on Carlson--Simpson's Ramsey theorem for partitions) and still 10% of epsilon-delta bullshit. This will also serve as a gentle introduction to the techniques for the (a bit trickier) proof of oscillation-stability of the Urysohn sphere, that I'll present next week. Best, David

Logic Seminar 18 Dec 2024 17:00 hrs at NUS by Manlio Valenti

NUS Logic Seminar

12/11/2024 23:41:55

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 18 Dec 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#05-11 Speaker: Manlio Valenti Title: On the density of the Weihrauch degrees Abstract: Recall that, in a partial order P, b is a minimal cover of a if the interval (a,b) is empty. A strengthening of this notion is the one of strong minimal cover, namely b is a strong minimal cover of a if c

Wednesday seminar

Abstract: Around 15 years ago, Newelski first observed a fundamental link between the model theory and dynamics. Since then many researchers have studied this connection is some form or another. Much of this research can be divided into studying two distinct group actions on certain spaces of types: (1) definable group actions or (2) automorphism group actions. We remark that while these settings are distinct and use different techniques, they also enjoy a kind of symmetry. Results on one side can inspire one to prove analogues results on the other.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 66th Nankai Logic Colloquium-- Kyle Gannon

Time: 16:00pm, Jan. 03, 2025(Beijing Time)

Zoom Number: 347 405 3484

Passcode: 477893

Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=95605149609

_____________________________________________________________________________________________________________________________________________________

This is the last Nankai Logic Colloquium of this semester. Happy new year and see you next semester!

Best regards,

Wei

Wednesday seminar

Prague Set Theory Seminar

1/2/2025 6:48:32

Dear all, The seminar meets on Wednesday January 8th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Ziemowit Kostana -- Generic Banach spaces with unconditional bases We study the properties of normed vector spaces obtained from forcing with finite, unconditional bases. These spaces are non-separable versions of the unconditional Pełczyński space, but due to genericity have strong rigidity features. This is a joint work in progress with Noe de Rancourt. Best, David PS: The early registration deadline for the Winter School is approaching. In case you intend to participate or you are considering it, please do register or let us know. https://winterschool.eu/2025

KGRC talks January 9

Kurt Godel Research Center

1/3/2025 8:52:19

KGRC/Institute of Mathematics invites you to the following talks: updates at https://kgrc.univie.ac.at/eventsnews/ Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, January 9, 11:30am--1:00pm, hybrid mode "Forcing on coding trees" N. Dobringen, Notre Dame du Lac, US In this talk, we will present Harrington's forcing proof of the Halpern-Läuchli Theorem and extensions to coding trees representing Fraïssé limits of free amalgamation (and certain strong amalgamation) classes with the Ramsey property. We will discuss several versions of such forcings and their various applications to infinite structural Ramsey theory. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, January 9, 3:00pm--3:50pm, hybrid mode "Infinite structural Ramsey theory and logic" N. Dobringen, Notre Dame du Lac, US The infinite Ramsey theorem states that given any coloring of all pairs of natural numbers into two colors, there is an infinite subset of natural numbers in which all pairs have the same color. When moving from sets to relational structures, some surprising phenomena occur: The prototypical example is that there is a coloring of pairs of rational numbers into two colors such that both colors persist in any subset of the rationals forming a dense linear order (Sierpiński, 1933). Likewise for colorings of edges in the Rado graph (Erdős–Hajnal–Pósa, 1975). The study of optimal bounds for finite colorings of copies (or embeddings) of a finite substructure inside an infinite structure is the subject of big Ramsey degrees. Optimal bounds are connected with structural expansions which produce analogues of the infinite Ramsey theorem; the pursuit of the optimal structural expansions has led to new connections between logic and structural Ramsey theory. This talk will introduce big Ramsey degrees, key examples, and components intrinsic to their characterizations, and touch on infinite-dimensional structural Ramsey theory ties in with topological Ramsey spaces. We will discuss various proof methods, including Milliken's strong tree theorem, Harrington's forcing proof of the Halpern-Läuchli Theorem, coding trees and forcing Ramsey theorems on them, parameter words, and others. The motivation for and progress of Ramsey theory on infinite structures are intrinsically intertwined with problems and methods in logic, including first-order logic, set theory, model theory, and computability theory. The expository paper [1] provides a gentle introduction to infinite structural Ramsey theory and an overview of the area. A plethora of other references will be included in the talk. [1] N. Dobrinen, “Ramsey theory of homogeneous structures: Current trends and open problems”. 2022 ICM—International Congress of Mathematicians. Vol. 3. Sections 1–4,1462–1486. Edited by D. Beliaev and S. Smirnov, EMS Press, Berlin, 2023. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recordings available so far of the Set Theory Seminar: Dec 5: P. Marun (Czech Academy of Sciences, Prague, CZ), "Labelled sets" https://ucloud.univie.ac.at/index.php/s/LTp6ZEJJr3CigQi Video recordings available so far of the Logic Colloquium: Dec 5: W. Chan (TU Wien), "Basis for Uncountable Linear Orders" https://ucloud.univie.ac.at/index.php/s/iendszDkS2wrLQB -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY - Special Announcement

This Week in Logic at CUNY

1/5/2025 21:27:00

Hi everyone,

I hope the New Year finds you well! Please note the special meeting of the Logic Workshop taking place on January 10th at 2pm.

All best,

Jonas

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

Logic Workshop
January 10, 2:00pm NY time, CUNY Graduate Center Room 4419

Jouko Väänänen, University of Helsinki
Categoricity arguments and their philosophical uses

Both number theory and set theory have a claim to categoricity, in one form or another, when axiomatized in second order logic. This goes back to Dedekind and Zermelo. It is less well-known that such claims manifest themselves also in first order axiomatizations, however non-categorical such axiomatizations are in the usual setup of mathematical logic (Väänänen, 'An extension of a theorem of Zermelo' BSL, 2019). Parsons and others have written about this e.g. in Parsons, 'The uniqueness of the natural numbers' (Jerusalem Philosophical Quarterly, 1990), and Button and Walsh, 'Philosophy and Model Theory' (Oxford University Press, 2018). We claim that philosophical uses of these arguments do not carry the philosophical weight they are purported to do. To support our claim we analyse the categoricity arguments in detail in the context of both first and second order logic. We expose a common factor of such arguments, internal categoricity, namely categoricity within what the theory in question, be it number theory or set theory, can see. While internal categoricity is a remarkable phenomenon in itself, we argue that it cannot be used to defend the decidability of formal statements in the theory. In conclusion, when categoricity results are used to make certain philosophical claims, even though the categoricity results are by and large correct, they do not support those claims.

Reference: Maddy and Väänänen: Philosophical Uses of Categoricity Arguments, Elements in the Philosophy of Mathematics. Cambridge University Press. (2023).

KGRC talks January 16

Kurt Godel Research Center

1/10/2025 5:54:49

KGRC/Institute of Mathematics invites you to the following talks: updates at https://kgrc.univie.ac.at/eventsnews/ Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, January 16, 11:30am--1:00pm, hybrid mode "Universal $\Delta$-metric spaces, Hall's group and Lévy groups" W. Dai (Nankai U, Tianjin, CN) In this talk, we study the isometry group $\textnormal{Iso}(\mathbb{U}_\Delta)$ of the $\Delta$-metric Urysohn space $\mathbb{U}_\Delta$ equipped with the pointwise convergence topology for a countable distance set $\Delta$ with $\inf\Delta=0$. We showed that $\textnormal{Iso}(\mathbb{U}_\Delta)$ is a Lévy group, so it is extremely amenable. Moreover, we can choose the Lévy family such that its increasing union is isomorphic to Hall's group. This generalizes the results that $\textnormal{Iso}(\mathbb{U})$ is Lévy by Pestov and $\textnormal{Iso}(\mathbb{U}_\Delta)$ contains a dense subgroup which is isomorphic to Hall's group by Etedadialiabadi, Gao, Le Maître and Melleray. Then we will discuss its analogy for the continuous logic case. It is an ongoing project with Su Gao and Víctor Hugo Yañez. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to aristotelis.panagiotopoulos@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern- Platz 1, 1090, 2nd floor, HS11, Thursday, January 16, 3pm--3:50pm, hybrid mode "Discrete and continuous translational monotilings" J. Grebik (Masaryk U, Brno, CZ) In this talk, I will survey results about translational monotilings of $\mathbb{Z}^d$ and $\mathbb{R}^d$, with a particular focus on the case $d \leq 2$. One of the central questions in this area is the decidability of the tiling problem. Closely related is the periodic tiling conjecture (PTC), which has been confirmed in $\mathbb{Z}^2$ by Bhattacharya but was recently disproved in high dimensions by Greenfeld and Tao. For $\mathbb{R}^2$, analogous questions remain open, even for polygonal sets. The most general result here is due to Kenyon, who established that PTC holds for topological disks. In ongoing work with de Dios Pont, Greenfeld, and Madrid, we show that translational monotilings by axis-parallel polygonal sets satisfy a weaker version of PTC and derive a decidability result in this context. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recordings available so far of the Logic Colloquium: Jan 9: N Dobrinen (Notre Dame du Lac, US), "Infinite structural Ramsey theory and logic" https://ucloud.univie.ac.at/index.php/s/8bqco4ptJHNLFP3 -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

Wednesday seminar

Prague Set Theory Seminar

1/10/2025 6:49:56

Dear all, The seminar meets on Wednesday January 15th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Adam Morawski -- An AD Family from a Parametrized Diamond In 2013 A.Aviles and P.Koszmider solved a long-standing problem concerning continuous images of Radon-Nikodým compact spaces. Together with Arturo Martinez-Celis we took a closer look at one of their constructions and pushed it to its limits. Using parametrized $\diamondsuit$-principles of Moore, Hrušák and Džamonja we construct an RN-compact space with an image which is not RN-compact while keeping the weight low. I already spoke about the topological side of the construction. In This talk I will go through the combinatorial/set theoretical proof. I will reintroduce the parametrized $\diamondsuit$. The bulk of the talk will be the construction of an almost disjoint family on $\omega_1$ with a certain combinatorial property. Best, David

Cross-Alps Logic Seminar for World Logic Day (speaker: Jouko Väänänen)

Cross-Alps Logic Seminar

1/13/2025 11:25:35

On Friday 17.01.2025 at 16:00

on the occasion of World Logic Day 2025, a special session of the Cross-Alps Logic Seminars will take place, with special guest
Jouko Väänänen (University of Helsinki)
who will give a talk on
Categoricity arguments and their philosophical uses

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

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

Wednesday seminar

Prague Set Theory Seminar

1/16/2025 7:01:33

Dear all, The seminar meets on Wednesday January 22nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Michael Hrusak -- Bounded topology We shall discuss a natural sequential topology on ideals stronger that the usual metric topology. There will be no seminar on Wednesday January 29th (Winter School). The seminar should meet again on Wednesday February 5th for a talk of Andy Zucker. You may also interested in the talk of Rob Sullivan on Tuesday next week https://www.math.cas.cz/index.php/events/event/3896 and a talk of Spencer Unger on Tuesday February 4th. https://www.math.cas.cz/index.php/events/event/3903 Best, David

KGRC talk January 23

Kurt Godel Research Center

1/17/2025 5:08:28

KGRC/Institute of Mathematics invites you to the following talk: updates at https://kgrc.univie.ac.at/eventsnews/ Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, January 23, 11:30am--1:00pm, hybrid mode "Rearrangement & subseries numbers" T. van der Vlugt (TU Wien) By rearranging the terms of a conditionally convergent series we can make it assume a different limit or even make it divergent. Similarly we could do so by taking a subseries of a conditionally convergent series. The rearrangement (and subseries) numbers are the least number of permutations (or subsets) of indices that are needed to change the behaviour of every conditionally convergent series. The rearrangement and subseries numbers are cardinal characteristics (cardinalities that are bound between $\aleph_1$ and the size of the continuum $2^{\aleph_0}$). In this talk we showcase various general tools (relational systems, Tukey connections, forcing) that are useful in the study of cardinal characteristics, we will give an overview of the family of rearrangement and subseries numbers, we will compare them to various well-known other cardinal characteristics, and we will introduce dual rearrangement and subseries numbers. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recording available so far of the Set Theory Seminar: Jan 16: W. Dai (Nankai U, Tianjin, CN), "Universal $\Delta$-metric spaces, Hall's group and Lévy groups" https://ucloud.univie.ac.at/index.php/s/xXq6rKtCnJ3R2ap -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

1/27/2025 9:09:56

Hi everyone, and welcome back! May the New Year bring positive change.

Future editions of this newsletter will be sent on Sunday evenings, as in the past. While many seminars resume next week, please note today's talk in the Rutgers Logic Seminar at 3:30pm.

Best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Jan 27, 2025 - - - -

Rutgers Logic Seminar
Monday January 27, 3:30pm, Rutgers University, Hill Center, Hill 705

Derek Levinson, UNT
PFA and Derived Models

- - - - Tuesday, Jan 28, 2025 - - - -

- - - - Wednesday, Jan 29, 2025 - - - -

- - - - Thursday, Jan 30, 2025 - - - -

- - - - Friday, Jan 31, 2025 - - - -

Next Week in Logic at CUNY:

- - - - Monday, Feb 3, 2025 - - - -

Logic and Metaphysics Workshop
NOTE NEW TIME AND ROOM

Date: Monday, February 3, 2-4pm (NY time)
Room: Graduate Center Room 7395
Noah Greenstein (Independent Scholar)

Rutgers Logic Seminar
Monday February 3, 3:30pm, Rutgers University, Hill Center, Hill 705
William Chan, TU Wien
Basis for Uncountable Linear Orders

- - - - Tuesday, Feb 4, 2025 - - - -

- - - - Wednesday, Feb 5, 2025 - - - -

- - - - Thursday, Feb 6, 2025 - - - -

- - - - Friday, Feb 7, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, February 7, 11:00am NY time, Room TBD
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Ali Enayat University of Gothenburg

Models of set theory: extensions and dead-ends

This is a two-part talk concerning existence/non-existence of certain kinds of extensions of arbitrary models of ZF, with no regard to countability or well-foundedness of the models involved. The talk is based a recent preprint: arXiv:2406.14790v1. The results presented include the following two. In Theorem A below, N is said to be a conservative elementary extension of M if N is an elementary extension of M with the property that the intersection of every parametrically definable subset of N with M is parametrically definable in M.
Theorem A. Every model M of ZF with a definable global well-ordering has a conservative elementary extension N that contains an ordinal above all of the ordinals of M.
Theorem B. Every consistent extension of ZF has a model of power aleph_1 that has no end extension to a model of ZF.

Model Theory Seminar
CUNY Graduate Center
Friday, February 7, 12:30pm NY time, Room: 5417 (NOTE ROOM CHANGE!)

Alf Dolich CUNY

Introduction to the model theory of the adeles and organization meeting

This first meeting will be partially devoted to organizing for the semester. But, I will also begin talking about Jamshid Derakhshan' survey paper on the model theory of the adeles entitled 'Model Theory of the Adeles and Number Theory'.

Logic Workshop
CUNY Graduate Center
Friday, February 7, 2:00pm-3:30pm, Room 5417 (NOTE ROOM CHANGE)

Assaf Shani Concordia 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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Wednesday seminar

Prague Set Theory Seminar

1/30/2025 3:22:38

Dear all, The seminar meets on Wednesday February 5th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There is a slight change of program, Andy Zucker's talk is postponed to Wednesday February 12th. There is also a couple of other events of interest which will take place in Prague next week. Spencer Unger will give a talk at the Tuesday morning Set Theory and Analysis seminar in Zitna, see here: https://www.math.cas.cz/index.php/events/event/3903 Gabor Kun will deliver a short course on measurable matchings at MFF in the Mala Strana building. Monday Feb 3, 2025 - room S6 - 13:10--15:00 Wednesday Feb 5, 2025 - room S7 - 13:10--15:00 Friday Feb 7, 2025 - room S6 - 10:40--13:00 The course is directed to all doctoral students and postdocs and will not assume any special previous knowledge. Program (Wednesday seminar Feb 5): Jan Grebik -- Lossless expansion and measure hyperfiniteness The notions of measure hyperfiniteness and measure reducibility of countable Borel equivalence relations are variants of the usual notions of hyperfiniteness and Borel reducibility. Conley and Miller proved that every basis for the countable Borel equivalence relations strictly above E_0 under measure reducibility is uncountable and asked whether there is a "measure successor of E_0"—i.e. a countable Borel equivalence relation E such that E is not measure reducible to E_0 and any F which is measure reducible to E is either equivalent to E or measure reducible to E_0. In an ongoing work with Patrick Lutz, we have isolated a combinatorial condition on a Borel group action (a strong form of expansion that we call "lossless expansion" after a similar property which is studied in computer science and finite combinatorics) which implies that the associated orbit equivalence relation is a measure successor of E_0. We have also found several examples of group actions which are plausible candidates for satisfying this condition. In this talk, I will explain the context for Conley and Miller's question, the condition that we have isolated and discuss some of the candidate examples we have identified. All of this is joint work with Patrick Lutz. Best, David

This Week in Logic at CUNY

2/2/2025 22:39:00

This Week in Logic at CUNY:

- - - - Monday, Feb 3, 2025 - - - -

Logic and Metaphysics Workshop
NOTE NEW TIME AND ROOM

Date: Monday, February 3, 2-4pm (NY time)
Room: Graduate Center Room 7395
Noah Greenstein (Independent Scholar)

Title: Existentialism, deontic logic and de dicto – de re

Abstract: I investigate how to logically formalize Existentialist obligations, i.e., obligations we have to ourselves and ourselves alone. It is argued that Standard Deontic Logic cannot distinguish between obligations imposed by an external system, like society or a theory of ethics, and self-imposed Existential obligations. A solution to this ambiguity is proposed by applying the De Dicto – De Re distinction to Deontic Logic in the style of Epistemic Logic: by varying the order of the existential quantifier and the modal operator, we can change the interpretation of the statement to represent Existential or external obligations. This leads to a kind of Formal Existentialism, where formal analysis can be applied to Existentialist claims, and new perspectives on standing problems in Deontic Logic.

Rutgers Logic Seminar
Monday February 3, 3:30pm, Rutgers University, Hill Center, Hill 705
William Chan, TU Wien
Basis for Uncountable Linear Orders

- - - - Tuesday, Feb 4, 2025 - - - -

- - - - Wednesday, Feb 5, 2025 - - - -

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: Raymond Puzio.

Date and Time: Wednesday February 5, 2025, 7:00 - 8:30 PM, Graduate Center Room 6417. IN PERSON TALK!!!

Title: Gentle Introduction to Synthetic Differential Geometry - Part 1.

Abstract: Calculations and constructions with infinitesimals make for a handy, intuitive way of doing calculus and differential geometry. They went out of favor in the nineteenth century when the real number system was defined precisely but were rehabilitated a century later when various people such as Robinson, Lawvere, and Kock realized that it is nonetheless possible to produce logically rigorous justifications for manipulations involving infinitesimals.

- - - - Thursday, Feb 6, 2025 - - - -

- - - - Friday, Feb 7, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, February 7, 11:00am NY time, Room TBD
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Ali Enayat University of Gothenburg

Models of set theory: extensions and dead-ends

This is a two-part talk concerning existence/non-existence of certain kinds of extensions of arbitrary models of ZF, with no regard to countability or well-foundedness of the models involved. The talk is based a recent preprint: arXiv:2406.14790v1. The results presented include the following two. In Theorem A below, N is said to be a conservative elementary extension of M if N is an elementary extension of M with the property that the intersection of every parametrically definable subset of N with M is parametrically definable in M.
Theorem A. Every model M of ZF with a definable global well-ordering has a conservative elementary extension N that contains an ordinal above all of the ordinals of M.
Theorem B. Every consistent extension of ZF has a model of power aleph_1 that has no end extension to a model of ZF.

Model Theory Seminar
CUNY Graduate Center
Friday, February 7, 12:30pm NY time, Room: 5417 (NOTE ROOM CHANGE!)

Alf Dolich CUNY

Introduction to the model theory of the adeles and organization meeting

This first meeting will be partially devoted to organizing for the semester. But, I will also begin talking about Jamshid Derakhshan' survey paper on the model theory of the adeles entitled 'Model Theory of the Adeles and Number Theory'.

Logic Workshop
CUNY Graduate Center
Friday, February 7, 2:00pm-3:30pm, Room 5417 (NOTE ROOM CHANGE)

Assaf Shani Concordia University

Generic dichotomies for Borel homomorphisms for the finite Friedman-Stanley jumps

The talk will begin by discussing the basic definitions and general goals behind the theory of Borel equivalence relations. We focus on the Friedman-Stanley jumps $= + n$ , for $n = 1, 2, . . .$ and $n = ω$ . These Borel equivalence relations represent the notions of being classifiable using invariants which are countable sets of reals, countable sets of countable sets of reals, and so on. We consider the problem of constructing a Borel reduction from $= + n$ to some other equivalence relation.

For $n = 1$ the situation is well understood and there are many such results. For example: Marker proved that for a first order theory with an uncountable type space, its isomorphism relation is above $= + 1$ ; Larson and Zapletal characterized the analytic equivalence relations above $= + 1$ as those which are 'unpinned' in the Solovay extension.

In this talk we present a new technique for proving that an equivalence relation is above $= + n$ , when $n > 1$ , based on Baire-category methods. As corollaries, we conclude that $= + ω$ is 'regular' (answering a question of Clemens), and that $= + n$ is 'in the spectrum of the meager ideal' (extending a result of Kanovei, Sabok, and Zapletal for $n = 1$ ).

Next Week in Logic at CUNY:

- - - - Monday, Feb 10, 2025 - - - -

Rutgers Logic Seminar
Monday February 10, 3:30pm, Rutgers University, Hill Center, Hill 705

Luke Serafin, Cornell

Logic and Metaphysics Workshop

Date: Monday, February 10, 2-4pm (NY time)
Room: Graduate Center Room 7395

Sergei Artemov (CUNY).
Title: Consistency of PA is a serial property, and it is provable in PA

Abstract: We revisit the question of whether the consistency of Peano Arithmetic PA can be established in PA and answer it affirmatively. Since PA-derivations are finite objects, their Gödel codes are standard natural numbers, and PA-consistency is equivalent to the series ConS(PA) of arithmetical formulas “n is not a code of a proof of 0 = 1” for numerals n = 0, 1, 2, … In contrast, in the consistency formula Con(PA) “for all x, x is not a proof of 0 = 1,” the quantifier “for all x” captures standard and nonstandard numbers, Con(PA) is strictly stronger than PA-consistency. Adopting Con(PA) as PA-consistency was a strengthening fallacy: the unprovability of Con(PA) does not yield the unprovability of PA-consistency. A proof of a serial property is a selector proof: prove that each instance has a proof. We selector prove ConS(PA) thus showing that PA-consistency is provable in PA. We discuss other theories and perspectives for Hilbert’s consistency program.

- - - - Tuesday, Feb 11, 2025 - - - -

- - - - Wednesday, Feb 12, 2025 - - - -

- - - - Thursday, Feb 13, 2025 - - - -

- - - - Friday, Feb 14, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, February 14, 11:00am NY time, Room TBD
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Ali Enayat University of Gothenburg

Models of set theory: extensions and dead-ends II

This is a two-part talk concerning existence/non-existence of certain kinds of extensions of arbitrary models of ZF, with no regard to countability or well-foundedness of the models involved. The talk is based a recent preprint: arXiv:2406.14790v1. The results presented include the following two. In Theorem A below, N is said to be a conservative elementary extension of M if N is an elementary extension of M with the property that the intersection of every parametrically definable subset of N with M is parametrically definable in M.
Theorem A. Every model M of ZF with a definable global well-ordering has a conservative elementary extension N that contains an ordinal above all of the ordinals of M.
Theorem B. Every consistent extension of ZF has a model of power aleph_1 that has no end extension to a model of ZF.

- - - - 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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Logic Seminar 5 February 2025 17:00 hrs at NUS

NUS Logic Seminar

2/3/2025 1:07:53

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 5 February 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Frank Stephan Title: Weakly represented families and domination properties Abstract: The talk presents joint work with David Belanger (Singapore), C.T.~Chong (Singapore), Rupert Hoelzl (Munich), Gordon Hoi (Singapore), Sanjay Jain (Singapore), Dilip Raghavan (Singapore), Frank Stephan (Singapore), Daniel Turetsky (Wellington) and Jing Zhang (Toronto) published in four papers. The first one dealt with comparing the growth behaviour of functions or families of functions partial-recursive relative to an oracle and classified oracles with respect to this measure. The second, third and fourth papers are about reverse mathematics and study weakly represented families, that are families of functions computed relative to some oracle in the second order part of the model (all functions in the family use the same oracle). These families are used as a tool to define notions like dominated (every weakly represented family is dominated by some function in the model), hyperimmune, biimmune and so on. Furthermore, one can such families also use as a hypothesis space for classes to be learnt - this extends the study to inductive inference. This is a survey talk with sample proofs. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar

2/6/2025 12:04:51

Dear all, The seminar meets on Wednesday February 12th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The seminar will probably not meet on Wednesday February 19th. Program: Andy Zucker --Topological groups with tractable minimal dynamics In joint work with Gianluca Basso, we explore the class of Polish groups whose universal minimal flows admit a comeager orbit. By work of Ben Yaacov, Melleray, and Tsankov, this class contains all Polish groups with metrizable universal minimal flow, and by an example of Kwiatkowska, this inclusion is strict. We isolate the correct generalization of this class of Polish groups to the class of all topological groups. We call these the topological groups with "tractable minimal dynamics (TMD)." One way of phrasing what makes this class "tractable" is an "abstract Kechris-Pestov-Todorcevic correspondence" which characterizes membership in TMD using a Ramsey-theoretic property of the group. In particular, this implies that TMD is absolute between models of set theory. We also state some conjectures to the effect that any topological group not in TMD has "wild" minimal dynamics. Best, David

This Week in Logic at CUNY

2/9/2025 22:29:00

This Week in Logic at CUNY:

- - - - Monday, Feb 10, 2025 - - - -

Rutgers Logic Seminar
Monday February 10, 3:30pm, Rutgers University, Hill Center, Hill 705

Luke Serafin, Cornell

Choice and Equitable Social Welfare

Logic and Metaphysics Workshop

Date: Monday, February 10, 2-4pm (NY time)
Room: Graduate Center Room 7395

Sergei Artemov (CUNY).
Title: Consistency of PA is a serial property, and it is provable in PA

Abstract: We revisit the question of whether the consistency of Peano Arithmetic PA can be established in PA and answer it affirmatively. Since PA-derivations are finite objects, their Gödel codes are standard natural numbers, and PA-consistency is equivalent to the series ConS(PA) of arithmetical formulas “n is not a code of a proof of 0 = 1” for numerals n = 0, 1, 2, … In contrast, in the consistency formula Con(PA) “for all x, x is not a proof of 0 = 1,” the quantifier “for all x” captures standard and nonstandard numbers, Con(PA) is strictly stronger than PA-consistency. Adopting Con(PA) as PA-consistency was a strengthening fallacy: the unprovability of Con(PA) does not yield the unprovability of PA-consistency. A proof of a serial property is a selector proof: prove that each instance has a proof. We selector prove ConS(PA) thus showing that PA-consistency is provable in PA. We discuss other theories and perspectives for Hilbert’s consistency program.

- - - - Tuesday, Feb 11, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, February 11, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Roman Kossak CUNY

Isomorphisms invariants for models of PA: part I.

- - - - Wednesday, Feb 12, 2025 - - - -

- - - - Thursday, Feb 13, 2025 - - - -

- - - - Friday, Feb 14, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, February 14, 11:00am NY time, Room TBD
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Ali Enayat University of Gothenburg

Models of set theory: extensions and dead-ends II

This is a two-part talk concerning existence/non-existence of certain kinds of extensions of arbitrary models of ZF, with no regard to countability or well-foundedness of the models involved. The talk is based a recent preprint: arXiv:2406.14790v1. The results presented include the following two. In Theorem A below, N is said to be a conservative elementary extension of M if N is an elementary extension of M with the property that the intersection of every parametrically definable subset of N with M is parametrically definable in M.
Theorem A. Every model M of ZF with a definable global well-ordering has a conservative elementary extension N that contains an ordinal above all of the ordinals of M.
Theorem B. Every consistent extension of ZF has a model of power aleph_1 that has no end extension to a model of ZF.

Model Theory Seminar
CUNY Graduate Center
Friday, February 14, 12:30pm NY time, Room: 5417

Alf Dolich, CUNY
Introduction to the model theory of the adeles: part II
I will continue talking about Derakhsan's survey article 'Model Theory of Adeles and Number Theory'.

Next Week in Logic at CUNY:

- - - - Monday, Feb 17, 2025 - - - -

*** GRADUATE CENTER CLOSED - PRESIDENT'S DAY ***

- - - - Tuesday, Feb 18, 2025 - - - -

- - - - Wednesday, Feb 19, 2025 - - - -

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: Jacob Szelko, Northeastern University.

Date and Time: Wednesday February 19, 2025, 7:00 - 8:30 PM. IN PERSON TALK!

Title: An Introduction to Compositional Public Health.

Abstract: Compositional public health is an emerging research field that exists to address the complexity in public health responses. The field lies at the intersection of category theory, epidemiology, and engineering and utilizes tools from applied category theory for public health applications. This talk will present the motivation of this field, an overview of the mathematics involved in its approaches, current state of the art, live demonstrations, and future research directions within this developing field.

- - - - Thursday, Feb 20, 2025 - - - -

Mathematics Department Colloquium
CUNY Graduate Center
Thursday, February 20, 2:00pm NY time, Room: 4214
Russell Miller, CUNY
Computability on R and Gal (Q)

This talk, in the Mathematics Department Colloquium of the CUNY Graduate Center, will be aimed at a broad mathematical audience.
Traditionally, computability theory has been restricted to countable structures (such as groups or rings). We explain how digital computation by Turing machines can be applied to continuum-sized structures, with particular attention to the real numbers and the absolute Galois group of the rationals, and present some natural and intriguing questions regarding each.

- - - - Friday, Feb 21, 2025 - - - -

Logic Workshop
CUNY Graduate Center
Friday, February 21, 2:00pm-3:30pm, Room 5417

Alf Dolich CUNY

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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Logic Seminar by Tatsuta Makoto on 19 Feb 2025 at 17:00 hrs

NUS Logic Seminar

2/10/2025 0:50:12

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 19 February 2025, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Tatsuta Makoto Title: Representation of Peano Arithmetic in Separation Logic URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Separation logic is successful for software verification of heap-manipulating programs. Numbers are necessary to be added to separation logic for verification of practical software where numbers are important. However, properties of the validity such as decidability and complexity for separation logic with numbers have not been fully studied yet. This paper presents the translation of Pi-0-1 formulas in Peano arithmetic to formulas in a small fragment of separation logic with numbers, which consists only of the intuitionistic points-to predicate, 0 and the successor function. Then this paper proves that a formula in Peano arithmetic is valid in the standard model if and only if its translation in this fragment is valid in the standard interpretation. As a corollary, this paper also gives a perspective proof for the undecidability of the validity in this fragment. Since Pi-0-1 formulas can describe consistency of logical systems and non-termination of computations, this result also shows that these properties discussed in Peano arithmetic can also be discussed in such a small fragment of separation logic with numbers.

This Week in Logic at CUNY

2/17/2025 11:16:56

This Week in Logic at CUNY:

- - - - Monday, Feb 17, 2025 - - - -

*** GRADUATE CENTER CLOSED - PRESIDENT'S DAY ***

- - - - Tuesday, Feb 18, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, February 18, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Roman Kossak CUNY

Isomorphisms invariants for models of PA: part II

- - - - Wednesday, Feb 19, 2025 - - - -

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: Jacob Szelko, Northeastern University.

Date and Time: Wednesday February 19, 2025, 7:00 - 8:30 PM. IN PERSON TALK!

Title: An Introduction to Compositional Public Health.

Abstract: Compositional public health is an emerging research field that exists to address the complexity in public health responses. The field lies at the intersection of category theory, epidemiology, and engineering and utilizes tools from applied category theory for public health applications. This talk will present the motivation of this field, an overview of the mathematics involved in its approaches, current state of the art, live demonstrations, and future research directions within this developing field.

- - - - Thursday, Feb 20, 2025 - - - -

Mathematics Department Colloquium
CUNY Graduate Center
Thursday, February 20, 2:00pm NY time, Room: 4214
Russell Miller, CUNY
Computability on R and Gal (Q)

This talk, in the Mathematics Department Colloquium of the CUNY Graduate Center, will be aimed at a broad mathematical audience.
Traditionally, computability theory has been restricted to countable structures (such as groups or rings). We explain how digital computation by Turing machines can be applied to continuum-sized structures, with particular attention to the real numbers and the absolute Galois group of the rationals, and present some natural and intriguing questions regarding each.

- - - - Friday, Feb 21, 2025 - - - -

Model Theory Seminar
CUNY Graduate Center
Friday, February 21, 12:30pm NY time, Room: 5417

Dave Marker, University of Illinois at Chicago
A uniform definition of in

We will discuss the paper of Cluckers, Derakhshan, Leeknegt and Macintyre on uniformly defining valuation rings in Henselian valued fields with finite or pseudofinite residue fields.

Logic Workshop
CUNY Graduate Center
Friday, February 21, 2:00pm-3:30pm, Room 5417

Alf Dolich, CUNY
Expansions of ordered Abelian groups of low rank

Expansions of the ordered additive group of the reals (or more generally definably complete expansions of ordered Abelian groups) of finite dp-rank are a class of reasonably well-behaved ordered structures that generalize the class of o-minimal structures. In this talk I will give a survey of ongoing work with John Goodrick on exploring the properties of definable sets in this class of structures.

Next Week in Logic at CUNY:

- - - - Monday, Feb 24, 2025 - - - -

Rutgers Logic Seminar
Monday February 24, 3:30pm, Rutgers University, Hill Center, Hill 705

Olga Kharlampovich, CUNY
First-order sentences in random groups

Logic and Metaphysics Workshop

Date: Monday, February 24, 2-4pm (NY time)
Room: Graduate Center Room 7395

Eduardo Fermé (Madeira)
Title: Belief change: An introduction

Abstract: The 1985 paper by Carlos Alchourrón (1931–1996), Peter Gärdenfors, and David Makinson (AGM), “On the Logic of Theory Change: Partial Meet Contraction and Revision Functions” was the starting-point of a large and rapidly growing literature that employs formal models in the investigation of changes in belief states and databases. In this talk, the first 40 years of this development are briefly summarized. The topics covered include equivalent characterizations of AGM operations, extended representations of the belief states, change operators not included in the original framework, iterated change, applications of the model, its connections with other formal frameworks, and criticism of the model.

- - - - Tuesday, Feb 25, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, February 25, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Roman Kossak, CUNY
Recursive saturation and resplendence

- - - - Wednesday, Feb 26, 2025 - - - -

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: Thiago Alexandre, TBA.
Date and Time: Wednesday February 26, 2025, 7:00 - 8:30 PM IN-PERSON TALK!!!.
Title: TBA.

- - - - Thursday, Feb 27, 2025 - - - -

- - - - Friday, Feb 28, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, February 28, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Andreas Lietz, TU Wien

Model Theory Seminar
CUNY Graduate Center
Friday, February 28, 12:30pm NY time, Room: 5417

Alf Dolich, CUNY
Introduction to the model theory of the adeles: part II
I will continue talking about Derakhsan's survey article 'Model Theory of Adeles and Number Theory'.

Logic Workshop
CUNY Graduate Center
Friday, February 28, 2:00pm-3:30pm, Room 5417

Filippo Calderoni, Rutgers University
Idealistic equivalence relations remastered

In recent work with Luca Motto Ros we prove that under analytic determinacy there exists an analytic relation that is not class-wise Borel embeddable into any orbit equivalence relation. The result builds on an unpublished result of Becker from 2001 and fits in the area of invariant descriptive set theory. I will mainly discuss our result and how it is related to a major conjecture in the field known as the ' $E 1$ conjecture'.

- - - - 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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67th Nankai Logic Colloquium

Nankai Logic Colloquium

2/18/2025 0:52:40

Hello everyone,

Welcome back to Nankai Logic Colloquium for the new semester! This week our weekly Nankai Logic Colloquium will be in the afternoon. Our speaker this week will be Zoltán Vidnyánszky from Eötvös Loránd University. This talk will take place this Friday, February 21st, from 4pm to 5pm (UTC+8, Beijing time).

Title: Towards understanding the complexity of Borel homomorphism problems

Abstract: The CSP dichotomy of Bulatov and Zhuk is a celebrated theorem of computer science: it states that given a finite structure H, deciding whether a structure G admits a homomorphism to G is either easy (in P) or hard (NP-complete). Since in the Borel context one can show that deciding Borel 3-colorability is strictly more complicated than 2-colorability, it was rather tempting to think that we will encounter the same split between easy and hard problems as in the mentioned finite case. I will show that this is not the case and discuss what could be the dividing line between easy and hard problems in the Borel setting.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 67th Nankai Logic Colloquium-- Zoltán Vidnyánszky

Time: 16:00pm, Feb.21, 2025(Beijing Time)

Zoom Number: 347 405 3484

Passcode: 477893

Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=98691178482

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Logic Seminar on 5 March 2025 17:00 hrs by Subin Pulari at NUS

NUS Logic Seminar

2/20/2025 5:01:39

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 05 March 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Subin Pulari Title: On the Compressibility of Real Numbers: New insights using exponential sums. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Measuring the informational content of real numbers has been a significant area of inquiry in algorithmic information theory. Finite-state compressibility (or finite-state dimension) of a real number is a value in [0, 1] which quantifies the amount of information/randomness in the real number as measured using finite-state automata. Finite-state dimension is the lower asymptotic ratio of compression achievable on an infinite string using information-lossless finite-state compressors. Interestingly, the finite-state dimension of a real number is also equal to the block Shannon entropy rate of the infinite sequence representing the expansion of the real number in a base b. A line of work, originating from Schnorr and Stimm (1972), has established that a number is Borel normal in base b if and only if its base b expansion has finite-state compressibility equal to 1, i.e., is incompressible. Hence, normal numbers are precisely the class of numbers that are incompressible using finite-state compressors. Most of the prior research on finite-state dimension has relied on combinatorial methods. In this talk we explore how tools from Fourier analysis can be employed to gain new insights into the compressibility of real numbers by solving an open question posed by Lutz and Mayordomo regarding the existence of absolutely dimensioned numbers. Absolutely normal numbers, being finite-state incompressible in every base of expansion, are precisely those numbers which have finite-state dimension equal to 1 in every base. At the other extreme, for example, every rational number has 0 finite-state dimension in every base. Generalizing this, Lutz and Mayordomo asked the following question: Does there exist any s strictly between 0 and 1 and a real number r such that r has finite state dimension equal to s in every base?. In this talk we use several tools involving exponential sums and techniques from Schmidt's work in 1960 to construct, for any given s in (0,1], a real number r having finite-state compressibility equal to s in every base. We also discuss further applications of exponential sums in analyzing and characterizing the finite-state compressibility of real numbers.

Wednesday seminar

Prague Set Theory Seminar

2/23/2025 9:28:29

Dear all, The seminar meets on Wednesday February 26th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet determined. (The backup may be me talking about something, probably some Ramsey stuff..) Best, David

This Week in Logic at CUNY

2/23/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Feb 24, 2025 - - - -

Rutgers Logic Seminar
Monday February 24, 3:30pm, Rutgers University, Hill Center, Hill 705

Olga Kharlampovich, CUNY
First-order sentences in random groups

Logic and Metaphysics Workshop

Date: Monday, February 24, 2-4pm (NY time)
Room: Graduate Center Room 7395

Eduardo Fermé (Madeira)
Title: Belief change: An introduction

Abstract: The 1985 paper by Carlos Alchourrón (1931–1996), Peter Gärdenfors, and David Makinson (AGM), “On the Logic of Theory Change: Partial Meet Contraction and Revision Functions” was the starting-point of a large and rapidly growing literature that employs formal models in the investigation of changes in belief states and databases. In this talk, the first 40 years of this development are briefly summarized. The topics covered include equivalent characterizations of AGM operations, extended representations of the belief states, change operators not included in the original framework, iterated change, applications of the model, its connections with other formal frameworks, and criticism of the model.

- - - - Tuesday, Feb 25, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, February 25, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Roman Kossak, CUNY
Recursive saturation and resplendence

- - - - Wednesday, Feb 26, 2025 - - - -

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: Thiago Alexandre, TBA.
Date and Time: Wednesday February 26, 2025, 7:00 - 8:30 PM IN-PERSON TALK!!!.

Title: Topological Derivators.

Abstract: The theory of derivators was originally developed by Grothendieck with high inspiration in topos cohomology. In a letter sent to Thomason, where he explains the main ideas and motivations guiding the formal reasoning of derivators, Grothendieck also remarks that those are Morita-invariant. This means that, if two small categories A and B have equivalent topoi of presheaves, then the categories D(A) and D(B ) are also equivalent for any derivator D. This observation suggests that it may be possible to extend any derivator D to the entire 2-category of topoi and geometric morphisms between them. Grothendieck conjectures that such an extension is always possible and essentially unique. In this case, every derivator D defined over small categories would be coming from a derivator D′ defined over topoi via natural equivalences of categories of the form D(A) = D′(A^), where A varies through small categories and A^ denotes the category of presheaves over A. However, despite these considerations, a theory of derivators over topoi has not yet been developed. To address this gap, I am currently developing a theory of topological derivators. With this theory, I aim to provide answers to Grothendieck’s conjecture. Beyond applications in geometry, the theory of topological derivators has strong connections to first-order categorical logic. In fact, it lies in the intersection between the later and homotopical algebra. In my talk, I would like to present the theory of topological derivators and some of its main results.

- - - - Thursday, Feb 27, 2025 - - - -

- - - - Friday, Feb 28, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, February 28, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Andreas Lietz, TU Wien
Equiconsistencies involving strengthenings of PFA

We discuss the famous open problem of determining the exact consistency strength of PFA. We present an equiconsistency between Ben Goodman's Sigma_n-Correct Proper Forcing Axiom, which implies PFA, and supercompact for C^(n-1)-cardinals under additional mild assumptions for large enough n. Without these assumptions we can prove a dichotomy resembling Woodin's HOD dichotomy with a model containing the mantle taking on the role of HOD.

Model Theory Seminar
CUNY Graduate Center
Friday, February 28, 12:30pm NY time, Room: 5417

Alf Dolich, CUNY
Introduction to the model theory of the adeles: part II
I will continue talking about Derakhsan's survey article 'Model Theory of Adeles and Number Theory'.

Logic Workshop
CUNY Graduate Center
Friday, February 28, 2:00pm-3:30pm, Room 5417

Filippo Calderoni, Rutgers University
Idealistic equivalence relations remastered

In recent work with Luca Motto Ros we prove that under analytic determinacy there exists an analytic relation that is not class-wise Borel embeddable into any orbit equivalence relation. The result builds on an unpublished result of Becker from 2001 and fits in the area of invariant descriptive set theory. I will mainly discuss our result and how it is related to a major conjecture in the field known as the ' conjecture'.

Next Week in Logic at CUNY:

- - - - Monday, Mar 3, 2025 - - - -

Logic and Metaphysics Workshop

Date: Monday, March 3, 2-4pm (NY time)
Room: Graduate Center Room 7395

Koji Tanaka (ANU)
Title: What’s so impossible about impossible worlds?

Abstract: Imagine a world where the laws of nature (or physics) are different from those in the actual world. In such a world, Usain Bolt might run faster than the speed of light. Graham Priest argues that such a world would be a physically impossible world. By analogy, a world where the laws of logic are different from those in the actual world is said to be a logically impossible world. But what’s so impossible about such a world? I argue that there is nothing impossible about a world that is merely different from the actual world. I will show that Priest’s position conflates how to evaluate modal statements with how to identify the actual world among all worlds. After rejecting Priest’s position, I will conclude by arguing that what makes a world impossible is not the difference in laws, but the violation of those laws.

Rutgers Logic Seminar
Monday March 3, 3:30pm, Rutgers University, Hill Center, Hill 705

Tom Benhamou, Rutgers

- - - - Tuesday, Mar 4, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 4, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Properties of elementary extensions
Athar Abdul-Quader Purchase College

- - - - Wednesday, Mar 5, 2025 - - - -

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: Grigorios Giotopoulos, NYU Abu Dhabi.
Date and Time: Wednesday March 5, 2025---- 10:00AM, ZOOM TALK!!!
Title: Thickened smooth sets as a natural setting for Lagrangian field theory.

Abstract: I will describe how a particularly convenient model for synthetic differential geometry -- the sheaf topos of infinitesimally thickened smooth sets -- serves as a powerful context to host classical Lagrangian field theory. As motivation, I will recall the textbook description of variational Lagrangian field theory, and list desiderata for an ambient category in which this can rigorously be formalized. I will then explain how sheaves over infinitesimally thickened Cartesian spaces naturally satisfy all the desiderata, and furthermore allow to rigorously formalize several more field theoretic concepts. Time permitting, I will indicate how the setting naturally generalizes to include the description of fermionic fields, and (gauge) fields with internal symmetries. This is based on joint work with Hisham Sati and Urs Schreiber.

- - - - Thursday, Mar 6, 2025 - - - -

- - - - Friday, Mar 7, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, March 7, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Tom Benhamou Rutgers University

Model Theory Seminar
CUNY Graduate Center
Friday, March 7, 12:30pm NY time, Room: 5417

Olga Kharlampovich, CUNY
First-order sentences in random groups

We prove that a random group, in Gromov's density model with , satisfies an AE sentence (in the language of groups) if and only if this sentence is true in a nonabelian free group. This is a joint work with R. Sklinos.

Logic Workshop
CUNY Graduate Center
Friday, March 7, 2:00pm-3:30pm, Room 5417

Maya Saran, Mathematics Foundation of America
A descriptive-set-theoretic result on sigma-ideals of compact sets

Polish spaces, the objects of study of descriptive set theory, are completely metrizable topological spaces that have a countable dense subset. For example, the reals - the first Polish space in the world. We will look at 'sigma-ideals' of compact subsets of a Polish space. Think of a sigma-ideal as being a collection of 'small' compact sets, under some notion of smallness -- so for example, your Polish space could be the interval and your sigma-ideal could be the collection of all its compact sets of Lebesgue measure . The descriptive-set-theoretic study of these objects yields rich results for the following reason. If you look at the collection of all the compact subsets of a Polish space, that too, topologized and metrized in a natural way, turns out to be a Polish space. This means that you can look at your sigma-ideal of compact sets in two places: in the original space, say , and in the `hyperspace' of all compact sets of . In this talk we will deal with sigma-ideals that can be represented in a very nice way inside this hyperspace, and we will examine the behaviour of so-called G-delta subsets of with respect to this representation.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

68th Nankai Logic Colloquium

Nankai Logic Colloquium

2/24/2025 3:41:11

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon. Our speaker this week will be Nan Fang from Institute of Software, CAS. This talk will take place this Friday, February 28th, from 4pm to 5pm (UTC+8, Beijing time).

Title: Extending CL-Reducibility on Array Noncomputable Degrees

Abstract: In the field of algorithmic randomness, cl-reducibility plays an important role. This reducibility is a variant of Turing reducibility where the use function is bounded from above by $\id+c$ where $\id$ is the identity function and $c$ is some constant.

In this talk, after introducing some basic results about cl-reducibility over array noncomputable degrees, I will show how these results can be extended from cl-reducibility to $(\id{+g})$-bounded-Turing reducibilities where $g$ is any computable nondecreasing function satisfying $\sum_n 2^{-g(n)} = \infty$.

Along with this, I will also introduce a modular approach for array noncomputable degrees, which could largely simplify the usual permitting constructions within these degrees.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 68th Nankai Logic Colloquium-- Nan Fang

Time: 16:00pm,Feb.28, 2025(Beijing Time)

Zoom Number: 347 405 3484

Passcode: 477893

Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=92319838540

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Wednesday seminar

Prague Set Theory Seminar

2/28/2025 8:06:51

Dear all, The seminar meets on Wednesday March 5th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Zdenek Silber -- Countably tight P(K) space with a nonseparable measure In the talk we focus on the relation of countable tightness of the space P(K) of Radon probability measures on a compact Hausdorff space K and of existence of measures in P(K) that have uncountable Maharam type. Recall that a topological space X has countable tightness if any element of the closure of a subset A of X lies in the closure of some countable subset of A. A Maharam type of a Radon probability measure mu is the density of the Banach spaceL1(mu). It was proven by Fremlin that, under Martin's axiom and negation of continuum hypothesis, for a compact Hausdorff space K the existence of a Radon probability of uncountable type is equivalent to the existence of a continuous surjection from K onto [0,1]^omega1. Hence, under such assumptions, countable tightness of P(K) implies that there is no Radon probability on K which has uncountable type. Later, Plebanek and Sobota showed that, without any additional set-theoretic assumptions, countable tightness of P(KxK) implies that there is no Radon probability on K which has uncountable type as well. It is thus natural to ask whether the implication "P(K) has countable tightness implies every Radon probability on K has countable type" holds in ZFC. I will present our joint result with Piotr Koszmider that under diamond principle there is a compact Hausdorff space K such that P(K) has countable tightness but there exists a Radon probability on K of uncountable type. Best, David

KGRC talks March 6

Kurt Godel Research Center

2/28/2025 11:20:28

KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) * * * * * * * * * Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, March 6, 11:30am--1:00pm, hybrid mode "The theory of symmetric systems and extensions I" J. Schilhan (U Wien) In this 3 talk series I will give an introduction to the technique of symmetric systems and present some of the recent results we have obtained joint with A. Karagila. Symmetric systems produce so called symmetric extensions which are intermediate models between $V$ and forcing extension $V[G]$. These models may not satisfy the Axiom of Choice and their primary use is to obtain consistency results for $\mathsf{ZF}$. On the other hand, they are also useful in generally understanding and classifying intermediate models. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Invitation to Damian Sobota's habilitation: Oskar-Morgenstern-Platz 1, Besprechungszimmer 02, 2nd floor Thursday, March 6, 2pm-2:45pm "On the complementability of the space $c_0$ in spaces of continuous functions" Please find here more information: https://mathematik.univie.ac.at/eventsnews/nachrichtenvolldarstellung/news/on-the-complementability-of-the-space-c-0-in-spaces-of-continuous-functions/?no_cache=1&cHash=7d9331213c9d0c6c971a8de48a03cbd0 -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

3/2/2025 22:41:00

This Week in Logic at CUNY:

- - - - Monday, Mar 3, 2025 - - - -

Logic and Metaphysics Workshop

Date: Monday, March 3, 2-4pm (NY time)
Room: Graduate Center Room 7395

Koji Tanaka (ANU)
Title: What’s so impossible about impossible worlds?

Abstract: Imagine a world where the laws of nature (or physics) are different from those in the actual world. In such a world, Usain Bolt might run faster than the speed of light. Graham Priest argues that such a world would be a physically impossible world. By analogy, a world where the laws of logic are different from those in the actual world is said to be a logically impossible world. But what’s so impossible about such a world? I argue that there is nothing impossible about a world that is merely different from the actual world. I will show that Priest’s position conflates how to evaluate modal statements with how to identify the actual world among all worlds. After rejecting Priest’s position, I will conclude by arguing that what makes a world impossible is not the difference in laws, but the violation of those laws.

Rutgers Logic Seminar
Monday March 3, 3:30pm, Rutgers University, Hill Center, Hill 705

Tom Benhamou, Rutgers

- - - - Tuesday, Mar 4, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 4, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Properties of elementary extensions
Athar Abdul-Quader Purchase College

Properties of elementary extensions

Computational Logic Seminar
Spring 2025 (in-person + zoom)
Tuesday, March 4, Time 2:00 - 4:00 PM, Graduate Center, rm. 3308

(Contact sartemov@gc.cuny.edu for zoom link)
Speaker: Benjamin PrudHomme, Graduate Center CUNY
Title: On Game Theory and Epistemic Logic

Abstract: Review of basic game theory and epistemic game theory concepts, including strictly competitive games, pure and mixed strategy Nash equilibria, rationalizability, models of knowledge, distinction between mutual and common knowledge. Review of proofs of when a game has a Nash equilibrium, Nash's Theorem, Muddy Children Problem, discussions of current and potential future efforts to utilize logic in developing a more comprehensive theory of pure strategy solutions.

- - - - Wednesday, Mar 5, 2025 - - - -

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: Grigorios Giotopoulos, NYU Abu Dhabi.
Date and Time: Wednesday March 5, 2025---- 10:00AM, ZOOM TALK!!!
Title: Thickened smooth sets as a natural setting for Lagrangian field theory.

Abstract: I will describe how a particularly convenient model for synthetic differential geometry -- the sheaf topos of infinitesimally thickened smooth sets -- serves as a powerful context to host classical Lagrangian field theory. As motivation, I will recall the textbook description of variational Lagrangian field theory, and list desiderata for an ambient category in which this can rigorously be formalized. I will then explain how sheaves over infinitesimally thickened Cartesian spaces naturally satisfy all the desiderata, and furthermore allow to rigorously formalize several more field theoretic concepts. Time permitting, I will indicate how the setting naturally generalizes to include the description of fermionic fields, and (gauge) fields with internal symmetries. This is based on joint work with Hisham Sati and Urs Schreiber.

- - - - Thursday, Mar 6, 2025 - - - -

- - - - Friday, Mar 7, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, March 7, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Tom Benhamou Rutgers University
Ultrafilters on measurables and non-measurables: discrepancies and techniques

We present new results regarding the depth and Tukey spectrum of general ultrafilters and simple
-points at a measurable cardinal. In particular we prove that on a measurable cardinal there can only be a single for which there exists a simple -point - this is in sharp contrast to . Finally we will present several models in which we analyze the depth and Tukey spectrum of an ultrafilter, and their effect on generalized cardinal characteristics.

Model Theory Seminar
CUNY Graduate Center
Friday, March 7, 12:30pm NY time, Room: 5417

Olga Kharlampovich, CUNY
First-order sentences in random groups

We prove that a random group, in Gromov's density model with , satisfies an AE sentence (in the language of groups) if and only if this sentence is true in a nonabelian free group. This is a joint work with R. Sklinos.

Logic Workshop
CUNY Graduate Center
Friday, March 7, 2:00pm-3:30pm, Room 5417

Maya Saran, Mathematics Foundation of America
A descriptive-set-theoretic result on sigma-ideals of compact sets

Polish spaces, the objects of study of descriptive set theory, are completely metrizable topological spaces that have a countable dense subset. For example, the reals - the first Polish space in the world. We will look at 'sigma-ideals' of compact subsets of a Polish space. Think of a sigma-ideal as being a collection of 'small' compact sets, under some notion of smallness -- so for example, your Polish space could be the interval and your sigma-ideal could be the collection of all its compact sets of Lebesgue measure . The descriptive-set-theoretic study of these objects yields rich results for the following reason. If you look at the collection of all the compact subsets of a Polish space, that too, topologized and metrized in a natural way, turns out to be a Polish space. This means that you can look at your sigma-ideal of compact sets in two places: in the original space, say , and in the `hyperspace' of all compact sets of . In this talk we will deal with sigma-ideals that can be represented in a very nice way inside this hyperspace, and we will examine the behaviour of so-called G-delta subsets of with respect to this representation.

Next Week in Logic at CUNY:

- - - - Monday, Mar 10, 2025 - - - -

Logic and Metaphysics Workshop

Date: Monday, March 10, 2-4pm (NY time)
Room: Graduate Center Room 7395

Rani Rachavelpula (Columbia)
Title: Generating gunk

Abstract: An object is gunky iff all its parts have proper parts. Since Anaxagoras, philosophers have appealed to the existence of gunk to support a range of metaphysical views. These discussions raise questions about the composition of gunk: How is gunk generated? How do we get gunk? Obviously, gunk cannot be composed of atoms. Otherwise, we have admitted objects into our ontology (i.e. atoms) with no proper parts. This has led to the widespread belief that gunk cannot be generated. It must be given. In this talk we prove this claim to be false. Though gunk cannot be generated by atoms, it can nevertheless be generated by some fundamental parts. We apply Weyl’s Equidistribution Theorem to produce a mereological model of a universe which is gunky yet generated by a single element. This dispels other misconceptions about gunk and provides a new perspective on debates about metaphysical fundamentality.

Rutgers Logic Seminar
Monday March 10, 3:30pm, Rutgers University, Hill Center, Hill 705

Ben-zion Weltsch, Rutgers

- - - - Tuesday, Mar 11, 2025 - - - -

- - - - Wednesday, Mar 12, 2025 - - - -

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: Jonathon Funk, Queensborough, CUNY.

Date and Time: Wednesday March 12, 2025, 7:00 - 8:30 PM. IN PERSON TALK

Title: Toposes and rings.

Abstract: I shall attempt to explain a part of a broader program of how topos theory and operator algebra theory match. Following the example of what I call a supported C*-algebra [1], such as a von Neumann algebra, we extend to an arbitrary ring the notions and constructions introduced there. (Familiarity with [1] is not necessary for the purposes of this talk.) I have included an explanation of the Zariski spectrum of a commutative ring in terms of the constructions I explain. Ultimately, our goal is to return to C*-algebras in order to generalize [1] to all C*-algebras, not just the supported ones.

This is joint work with Simon Henry.

[1] J. Funk, Toposes and C*-algebras, preprint, March 2024.

- - - - Thursday, Mar 13, 2025 - - - -

- - - - Friday, Mar 14, 2025 - - - -

Logic Workshop
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417

Alex Kruckman Wesleyan University

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

69th Nankai Logic Colloquium

Nankai Logic Colloquium

3/3/2025 8:50:56

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Clinton T. Conley from Carnegie Mellon University. This talk will take place this Friday, March 7th, from 9am to 10am (UTC+8, Beijing time).

Title: Measurable 2-factors of regular bipartite graphs

Abstract: We consider the problem of finding a 2-regular subgraph of a given regular graph with no odd cycles. We show that this is always possible in the BP context. As a consequence, odd-regular bipartite Borel graphs on Polish spaces admit perfect matchings with the property of Baire, in contrast with recent examples of Kun in the measure-theoretic setting. Analogous results in the measure-theoretic context hold for hyperfinite graphs. This is joint work with Matt Bowen and Felix Weilacher, building upon prior joint work with Kechris and with Miller.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 69th Nankai Logic Colloquium-- Clinton T. Conley Time: 9:00am,Mar. 07, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=93623622953

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Cross-Alps Logic Seminar (speaker: Sumun Iyer)

Cross-Alps Logic Seminar

3/3/2025 10:17:19

On Friday 07.03.2025 at 16.00 CET

Sumun Iyer (Carnegie Mellon University)

will give a talk on

Extremely amenable groups of homeomorphisms

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

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

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

KGRC talks March 13

Kurt Godel Research Center

3/7/2025 5:35:21

KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, March 6, 11:30am--1:00pm, hybrid mode "The theory of symmetric systems and extensions II" J. Schilhan (U Wien) In this 3 talk series I will give an introduction to the technique of symmetric systems and present some of the recent results we have obtained joint with A. Ka9ragila. Symmetric systems produce so called symmetric extensions which are intermediate models between $V$ and forcing extension $V[G]$. These models may not satisfy the Axiom of Choice and their primary use is to obtain consistency results for $\mathsf{ZF}$. On the other hand, they are also useful in generally understanding and classifying intermediate models. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, March 13, 3:00pm--3:50pm, hybrid mode "Classification of 3-manifolds" M. Iannella (TU Wien) A classification problem consists of a set of mathematical objects equipped with some natural equivalence relation; a solution to such a problem is an assignment of complete invariants. In this talk we consider the problem of classifying 3-manifolds up to homeomorphism from the perspective of descriptive set theory. We briefly discuss the framework of Borel reducibility, a standard tool for comparing the complexity of different classification problems, and present our recent result which determines the exact complexity of the classification of non-compact 3-manifolds up to homeomorphism. This is joint work in progress with Vadim Weinstein (Oulu). Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recording available so far of the Set Theory Seminar: Mar 6: J. Schilhan (U Wien): "The theory of symmetric systems and extensions I" https://ucloud.univie.ac.at/index.php/s/A4N6nk98mRoSn4T -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

3/9/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Mar 10, 2025 - - - -

Logic and Metaphysics Workshop

Date: Monday, March 10, 2-4pm (NY time)
Room: Graduate Center Room 7395

Rani Rachavelpula (Columbia)
Title: Generating gunk

Abstract: An object is gunky iff all its parts have proper parts. Since Anaxagoras, philosophers have appealed to the existence of gunk to support a range of metaphysical views. These discussions raise questions about the composition of gunk: How is gunk generated? How do we get gunk? Obviously, gunk cannot be composed of atoms. Otherwise, we have admitted objects into our ontology (i.e. atoms) with no proper parts. This has led to the widespread belief that gunk cannot be generated. It must be given. In this talk we prove this claim to be false. Though gunk cannot be generated by atoms, it can nevertheless be generated by some fundamental parts. We apply Weyl’s Equidistribution Theorem to produce a mereological model of a universe which is gunky yet generated by a single element. This dispels other misconceptions about gunk and provides a new perspective on debates about metaphysical fundamentality.

Rutgers Logic Seminar
Monday March 10, 3:30pm, Rutgers University, Hill Center, Hill 705

Ben-zion Weltsch, Rutgers
Galvin's Failure on Supercompactness Measures

- - - - Tuesday, Mar 11, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 11, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Minimal elementary extensions
Athar Abdul-Quader Purchase College

Computational Logic Seminar
Spring 2025 (in-person + zoom)

Tuesday, March 11

Time 2:00 - 4:00 PM

Graduate Center, rm. 3308

Speaker: Melvin Fitting, Graduate Center CUNY

Title: Semantic Tableaus I.

Abstract: Tableau systems are intuitively natural proof procedures, and have been formulated for quite a number of logics. Because of their inherent design, they serve well for proof discovery. The basic and most familiar tableau system is for classical logic, and I will begin with it. This will be followed by intuitionistic logic, and finally by several kinds of tableau systems for modal logics. I will also mention how the machinery can be adapted for some well-known non-classical many-valued logics. I will briefly discuss connections between tableau and sequent calculi. The presentation will be propositional. If there is time, I will sketch how quantification can be added, but that is really a topic in itself. The presentation is spread over two sessions.

- - - - Wednesday, Mar 12, 2025 - - - -

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: Jonathon Funk, Queensborough, CUNY.

Date and Time: Wednesday March 12, 2025, 7:00 - 8:30 PM. IN PERSON TALK

Title: Toposes and rings.

Abstract: I shall attempt to explain a part of a broader program of how topos theory and operator algebra theory match. Following the example of what I call a supported C*-algebra [1], such as a von Neumann algebra, we extend to an arbitrary ring the notions and constructions introduced there. (Familiarity with [1] is not necessary for the purposes of this talk.) I have included an explanation of the Zariski spectrum of a commutative ring in terms of the constructions I explain. Ultimately, our goal is to return to C*-algebras in order to generalize [1] to all C*-algebras, not just the supported ones.

This is joint work with Simon Henry.

[1] J. Funk, Toposes and C*-algebras, preprint, March 2024.

- - - - Thursday, Mar 13, 2025 - - - -

- - - - Friday, Mar 14, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, March 14, 12:30pm NY time, Room: 5417

A three body problem in stable (and simple and NSOP_1) theories

A few years ago, a problem arose in some of my work that I wasn’t able to solve, forcing me to add a technical hypothesis to a theorem - this has bothered me ever since. The issue has to do with the relationship between independence in a stable (or simple or NSOP_1) theory and independence in a stable reduct. In this rather informal talk, I will describe the problem and some partial results. The audience is welcome to provide proofs or counterexamples.

Logic Workshop
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417

Alex Kruckman Wesleyan University

Recall that a structure is pseudofinite if every sentence satisfied by that structure has a finite model - equivalently, if the structure is elementarily equivalent to an ultraproduct of finite structures. In this talk, I will present some work in progress from two independent projects around pseudofinite rings and pseudofinite modules: one is joint work with Alex Van Abel, the other is work of my PhD student Roberto Torres. These two projects are linked by the important role played by the class of von Neumann regular rings.

Next Week in Logic at CUNY:

- - - - Monday, Mar 17, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 3, 2-4pm (NY time)
Room: Graduate Center Room 7395

Greg Restall (St Andrews).
Title: Modal logic and contingent existence

Abstract: In this talk, I will defend contingentism, the idea that some things exist contingently. It might be surprising that this needs defence, but natural reasoning principles concerning possibility and necessity on the one hand, and the existential and universal quantifiers on the other, have led some to necessitism, the view that everything that exists, exists necessarily. Almost all recent work on modal semantics makes essential use of possible worlds models. These models have proved useful for analysing the structural properties of modal logics, but it is less clear that they fix the meaning of our modal vocabulary, given that we have no grasp of what counts as a possible world, independent of our grasp of what counts as possible. In this talk, I describe an inferentialist semantics for modal and quantificational vocabulary, not as a rival to possible worlds models, but as an explanation of how the concepts we do employ can be modelled using possible worlds. I then use this inferentialist semantics to clarify the contingentist’s commitments, and offer answers to necessitist objections.

- - - - Tuesday, Mar 18, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 11, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Scott Sets in algebraic settings
Alf Dolich CUNY

- - - - Wednesday, Mar 19, 2025 - - - -

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: Sophie d'Espalungue.
Date and Time: Wednesday March 19, 2025, 2:00 - 3:00 PM. Zoom talk. NOTE SPECIAL TIME!!
Title: Building All of Mathematics Without Axioms: An n-Categorical Manifesto.

- - - - Thursday, Mar 20, 2025 - - - -

- - - - Friday, Mar 21, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, March 21, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Tristan van der Vlugt, TU Wien
Meagre and Null Ideals for Uncountable Cardinals

We will consider the space of functions from to for various choices of and . In the first part of the talk we define topologies on such spaces and discuss the -meagre ideal (i.e. sets that are unions of -many nowhere dense sets), and their associated cardinal invariants. In the second part, we will look at various ways to consider (cardinal invariants of) the null ideal on such spaces.

Model Theory Seminar

CUNY Graduate Center
Friday, March 21, 12:30pm NY time, Room: 5417

Vince Guingona Towson University

Logic Workshop

CUNY Graduate Center
Friday, March 21, 2:00pm-3:30pm, Room 5417

Sheila Miller Edwards Arizona State University

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Wednesday seminar

Prague Set Theory Seminar

3/10/2025 6:23:52

Dear all, The seminar meets on Wednesday March 12th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet determined, the backup option might be me continuing the talk from two weeks ago and repeating/fixing the proof of the pigeon principle for the Ramsey space for the pseudotree, this time using a Harrington type (forcing) argument. Best, David

70th Nankai Logic Colloquium

Nankai Logic Colloquium

3/10/2025 12:07:40

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Spencer Unger from the University of Toronto. This talk will take place this Friday, March 14th, from 9am to 10am (UTC+8, Beijing time).

Title: Equidecomposition and discrepancy

Abstract: We will survey some recent results on equidecomposition in the torus. An important component of these results is the notion of discrepancy. In its simplest form, discrepancy for a measure $\mu$ is the supremum over intervals $I$ of $\vert \mu(I) - \lambda(I) \vert$ where $\lambda$ is Lebesgue measure. The theme of the talk is that numerical bounds on discrepancy for a sequence of measures $\mu_n$ can be used as input to (measurable) solutions to problems of equidecomposibility. This talk will contain joint work with Anush Tserunyan and Anton Bernshteyn and with Andrew Marks.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 70th Nankai Logic Colloquium-- Spencer Unger Time: 9:00am, Mar. 14, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=97039931937

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

UPDATE - This Week in Logic at CUNY

This Week in Logic at CUNY

3/10/2025 16:00:00

Hi everyone,

Note I have added missing information to two talks taking place this Friday (Model Theory Seminar and Logic Workshop). Apologies for the omissions!

Best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Mar 10, 2025 - - - -

Logic and Metaphysics Workshop

Date: Monday, March 10, 2-4pm (NY time)
Room: Graduate Center Room 7395

Rani Rachavelpula (Columbia)
Title: Generating gunk

Abstract: An object is gunky iff all its parts have proper parts. Since Anaxagoras, philosophers have appealed to the existence of gunk to support a range of metaphysical views. These discussions raise questions about the composition of gunk: How is gunk generated? How do we get gunk? Obviously, gunk cannot be composed of atoms. Otherwise, we have admitted objects into our ontology (i.e. atoms) with no proper parts. This has led to the widespread belief that gunk cannot be generated. It must be given. In this talk we prove this claim to be false. Though gunk cannot be generated by atoms, it can nevertheless be generated by some fundamental parts. We apply Weyl’s Equidistribution Theorem to produce a mereological model of a universe which is gunky yet generated by a single element. This dispels other misconceptions about gunk and provides a new perspective on debates about metaphysical fundamentality.

Rutgers Logic Seminar
Monday March 10, 3:30pm, Rutgers University, Hill Center, Hill 705

Ben-zion Weltsch, Rutgers
Galvin's Failure on Supercompactness Measures

- - - - Tuesday, Mar 11, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 11, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Minimal elementary extensions
Athar Abdul-Quader Purchase College

Computational Logic Seminar
Spring 2025 (in-person + zoom)

Tuesday, March 11

Time 2:00 - 4:00 PM

Graduate Center, rm. 3308

Speaker: Melvin Fitting, Graduate Center CUNY

Title: Semantic Tableaus I.

Abstract: Tableau systems are intuitively natural proof procedures, and have been formulated for quite a number of logics. Because of their inherent design, they serve well for proof discovery. The basic and most familiar tableau system is for classical logic, and I will begin with it. This will be followed by intuitionistic logic, and finally by several kinds of tableau systems for modal logics. I will also mention how the machinery can be adapted for some well-known non-classical many-valued logics. I will briefly discuss connections between tableau and sequent calculi. The presentation will be propositional. If there is time, I will sketch how quantification can be added, but that is really a topic in itself. The presentation is spread over two sessions.

- - - - Wednesday, Mar 12, 2025 - - - -

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: Jonathon Funk, Queensborough, CUNY.

Date and Time: Wednesday March 12, 2025, 7:00 - 8:30 PM. IN PERSON TALK

Title: Toposes and rings.

Abstract: I shall attempt to explain a part of a broader program of how topos theory and operator algebra theory match. Following the example of what I call a supported C*-algebra [1], such as a von Neumann algebra, we extend to an arbitrary ring the notions and constructions introduced there. (Familiarity with [1] is not necessary for the purposes of this talk.) I have included an explanation of the Zariski spectrum of a commutative ring in terms of the constructions I explain. Ultimately, our goal is to return to C*-algebras in order to generalize [1] to all C*-algebras, not just the supported ones.

This is joint work with Simon Henry.

[1] J. Funk, Toposes and C*-algebras, preprint, March 2024.

- - - - Thursday, Mar 13, 2025 - - - -

- - - - Friday, Mar 14, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, March 14, 12:30pm NY time, Room: 5417

A three body problem in stable (and simple and NSOP_1) theories
Alex Kruckman Wesleyan University

A few years ago, a problem arose in some of my work that I wasn’t able to solve, forcing me to add a technical hypothesis to a theorem - this has bothered me ever since. The issue has to do with the relationship between independence in a stable (or simple or NSOP_1) theory and independence in a stable reduct. In this rather informal talk, I will describe the problem and some partial results. The audience is welcome to provide proofs or counterexamples.

Logic Workshop
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417

Some pseudofinite rings and modules

Alex Kruckman Wesleyan University

Recall that a structure is pseudofinite if every sentence satisfied by that structure has a finite model - equivalently, if the structure is elementarily equivalent to an ultraproduct of finite structures. In this talk, I will present some work in progress from two independent projects around pseudofinite rings and pseudofinite modules: one is joint work with Alex Van Abel, the other is work of my PhD student Roberto Torres. These two projects are linked by the important role played by the class of von Neumann regular rings.

Next Week in Logic at CUNY:

- - - - Monday, Mar 17, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 3, 2-4pm (NY time)
Room: Graduate Center Room 7395

Greg Restall (St Andrews).
Title: Modal logic and contingent existence

Abstract: In this talk, I will defend contingentism, the idea that some things exist contingently. It might be surprising that this needs defence, but natural reasoning principles concerning possibility and necessity on the one hand, and the existential and universal quantifiers on the other, have led some to necessitism, the view that everything that exists, exists necessarily. Almost all recent work on modal semantics makes essential use of possible worlds models. These models have proved useful for analysing the structural properties of modal logics, but it is less clear that they fix the meaning of our modal vocabulary, given that we have no grasp of what counts as a possible world, independent of our grasp of what counts as possible. In this talk, I describe an inferentialist semantics for modal and quantificational vocabulary, not as a rival to possible worlds models, but as an explanation of how the concepts we do employ can be modelled using possible worlds. I then use this inferentialist semantics to clarify the contingentist’s commitments, and offer answers to necessitist objections.

- - - - Tuesday, Mar 18, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 11, 1pm (NY time), CUNY Graduate Center, Room: 4214.03

Scott Sets in algebraic settings
Alf Dolich CUNY

- - - - Wednesday, Mar 19, 2025 - - - -

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: Sophie d'Espalungue.
Date and Time: Wednesday March 19, 2025, 2:00 - 3:00 PM. Zoom talk. NOTE SPECIAL TIME!!
Title: Building All of Mathematics Without Axioms: An n-Categorical Manifesto.

- - - - Thursday, Mar 20, 2025 - - - -

- - - - Friday, Mar 21, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, March 21, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Tristan van der Vlugt, TU Wien
Meagre and Null Ideals for Uncountable Cardinals

We will consider the space of functions from to for various choices of and . In the first part of the talk we define topologies on such spaces and discuss the -meagre ideal (i.e. sets that are unions of -many nowhere dense sets), and their associated cardinal invariants. In the second part, we will look at various ways to consider (cardinal invariants of) the null ideal on such spaces.

Model Theory Seminar

CUNY Graduate Center
Friday, March 21, 12:30pm NY time, Room: 5417

Vince Guingona Towson University

Logic Workshop

CUNY Graduate Center
Friday, March 21, 2:00pm-3:30pm, Room 5417

Sheila Miller Edwards Arizona State University

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

UPDATE 2: This Week in Logic at CUNY

This Week in Logic at CUNY

3/11/2025 9:35:38

One more last minute correction - today's Models of Peano Arithmetic (MOPA) talk will take place at 10:30am (rather than 1pm as previously stated). If you hurry you can still make it!

Best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Mar 10, 2025 - - - -

Logic and Metaphysics Workshop

Date: Monday, March 10, 2-4pm (NY time)
Room: Graduate Center Room 7395

Rani Rachavelpula (Columbia)
Title: Generating gunk

Abstract: An object is gunky iff all its parts have proper parts. Since Anaxagoras, philosophers have appealed to the existence of gunk to support a range of metaphysical views. These discussions raise questions about the composition of gunk: How is gunk generated? How do we get gunk? Obviously, gunk cannot be composed of atoms. Otherwise, we have admitted objects into our ontology (i.e. atoms) with no proper parts. This has led to the widespread belief that gunk cannot be generated. It must be given. In this talk we prove this claim to be false. Though gunk cannot be generated by atoms, it can nevertheless be generated by some fundamental parts. We apply Weyl’s Equidistribution Theorem to produce a mereological model of a universe which is gunky yet generated by a single element. This dispels other misconceptions about gunk and provides a new perspective on debates about metaphysical fundamentality.

Rutgers Logic Seminar
Monday March 10, 3:30pm, Rutgers University, Hill Center, Hill 705

Ben-zion Weltsch, Rutgers
Galvin's Failure on Supercompactness Measures

- - - - Tuesday, Mar 11, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 11, 10:30am (NY time), CUNY Graduate Center, Room: 4214.03

Minimal elementary extensions
Athar Abdul-Quader Purchase College

Computational Logic Seminar
Spring 2025 (in-person + zoom)

Tuesday, March 11

Time 2:00 - 4:00 PM

Graduate Center, rm. 3308

Speaker: Melvin Fitting, Graduate Center CUNY

Title: Semantic Tableaus I.

Abstract: Tableau systems are intuitively natural proof procedures, and have been formulated for quite a number of logics. Because of their inherent design, they serve well for proof discovery. The basic and most familiar tableau system is for classical logic, and I will begin with it. This will be followed by intuitionistic logic, and finally by several kinds of tableau systems for modal logics. I will also mention how the machinery can be adapted for some well-known non-classical many-valued logics. I will briefly discuss connections between tableau and sequent calculi. The presentation will be propositional. If there is time, I will sketch how quantification can be added, but that is really a topic in itself. The presentation is spread over two sessions.

- - - - Wednesday, Mar 12, 2025 - - - -

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: Jonathon Funk, Queensborough, CUNY.

Date and Time: Wednesday March 12, 2025, 7:00 - 8:30 PM. IN PERSON TALK

Title: Toposes and rings.

Abstract: I shall attempt to explain a part of a broader program of how topos theory and operator algebra theory match. Following the example of what I call a supported C*-algebra [1], such as a von Neumann algebra, we extend to an arbitrary ring the notions and constructions introduced there. (Familiarity with [1] is not necessary for the purposes of this talk.) I have included an explanation of the Zariski spectrum of a commutative ring in terms of the constructions I explain. Ultimately, our goal is to return to C*-algebras in order to generalize [1] to all C*-algebras, not just the supported ones.

This is joint work with Simon Henry.

[1] J. Funk, Toposes and C*-algebras, preprint, March 2024.

- - - - Thursday, Mar 13, 2025 - - - -

- - - - Friday, Mar 14, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, March 14, 12:30pm NY time, Room: 5417

A three body problem in stable (and simple and NSOP_1) theories
Alex Kruckman Wesleyan University

A few years ago, a problem arose in some of my work that I wasn’t able to solve, forcing me to add a technical hypothesis to a theorem - this has bothered me ever since. The issue has to do with the relationship between independence in a stable (or simple or NSOP_1) theory and independence in a stable reduct. In this rather informal talk, I will describe the problem and some partial results. The audience is welcome to provide proofs or counterexamples.

Logic Workshop
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417

Some pseudofinite rings and modules

Alex Kruckman Wesleyan University

Recall that a structure is pseudofinite if every sentence satisfied by that structure has a finite model - equivalently, if the structure is elementarily equivalent to an ultraproduct of finite structures. In this talk, I will present some work in progress from two independent projects around pseudofinite rings and pseudofinite modules: one is joint work with Alex Van Abel, the other is work of my PhD student Roberto Torres. These two projects are linked by the important role played by the class of von Neumann regular rings.

Next Week in Logic at CUNY:

- - - - Monday, Mar 17, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 3, 2-4pm (NY time)
Room: Graduate Center Room 7395

Greg Restall (St Andrews).
Title: Modal logic and contingent existence

Abstract: In this talk, I will defend contingentism, the idea that some things exist contingently. It might be surprising that this needs defence, but natural reasoning principles concerning possibility and necessity on the one hand, and the existential and universal quantifiers on the other, have led some to necessitism, the view that everything that exists, exists necessarily. Almost all recent work on modal semantics makes essential use of possible worlds models. These models have proved useful for analysing the structural properties of modal logics, but it is less clear that they fix the meaning of our modal vocabulary, given that we have no grasp of what counts as a possible world, independent of our grasp of what counts as possible. In this talk, I describe an inferentialist semantics for modal and quantificational vocabulary, not as a rival to possible worlds models, but as an explanation of how the concepts we do employ can be modelled using possible worlds. I then use this inferentialist semantics to clarify the contingentist’s commitments, and offer answers to necessitist objections.

- - - - Tuesday, Mar 18, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 11, 10:30am (NY time), CUNY Graduate Center, Room: 4214.03

Scott Sets in algebraic settings
Alf Dolich CUNY

- - - - Wednesday, Mar 19, 2025 - - - -

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: Sophie d'Espalungue.
Date and Time: Wednesday March 19, 2025, 2:00 - 3:00 PM. Zoom talk. NOTE SPECIAL TIME!!
Title: Building All of Mathematics Without Axioms: An n-Categorical Manifesto.

- - - - Thursday, Mar 20, 2025 - - - -

- - - - Friday, Mar 21, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, March 21, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Tristan van der Vlugt, TU Wien
Meagre and Null Ideals for Uncountable Cardinals

We will consider the space of functions from to for various choices of and . In the first part of the talk we define topologies on such spaces and discuss the -meagre ideal (i.e. sets that are unions of -many nowhere dense sets), and their associated cardinal invariants. In the second part, we will look at various ways to consider (cardinal invariants of) the null ideal on such spaces.

Model Theory Seminar

CUNY Graduate Center
Friday, March 21, 12:30pm NY time, Room: 5417

Vince Guingona Towson University

Logic Workshop

CUNY Graduate Center
Friday, March 21, 2:00pm-3:30pm, Room 5417

Sheila Miller Edwards Arizona State University

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

UPDATE 3: This Week in Logic at CUNY

This Week in Logic at CUNY

3/13/2025 11:38:57

Another update - on Monday 3/17 the Logic and Metaphysics workshop will hold back-to-back talks at 2pm (Davide Sutto, Oslo) and 4pm (Greg Restall, St Andrews), details below.

All best,

Jonas

(The rest of) This Week in Logic at CUNY:

- - - - Thursday, Mar 13, 2025 - - - -

- - - - Friday, Mar 14, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, March 14, 12:30pm NY time, Room: 5417

A three body problem in stable (and simple and NSOP_1) theories
Alex Kruckman Wesleyan University

A few years ago, a problem arose in some of my work that I wasn’t able to solve, forcing me to add a technical hypothesis to a theorem - this has bothered me ever since. The issue has to do with the relationship between independence in a stable (or simple or NSOP_1) theory and independence in a stable reduct. In this rather informal talk, I will describe the problem and some partial results. The audience is welcome to provide proofs or counterexamples.

Logic Workshop
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417

Some pseudofinite rings and modules

Alex Kruckman Wesleyan University

Recall that a structure is pseudofinite if every sentence satisfied by that structure has a finite model - equivalently, if the structure is elementarily equivalent to an ultraproduct of finite structures. In this talk, I will present some work in progress from two independent projects around pseudofinite rings and pseudofinite modules: one is joint work with Alex Van Abel, the other is work of my PhD student Roberto Torres. These two projects are linked by the important role played by the class of von Neumann regular rings.

Next Week in Logic at CUNY:

- - - - Monday, Mar 17, 2025 - - - -

Logic and Metaphysics Workshop (NOTE BACK-TO-BACK TALKS TODAY)
Date: Monday, March 17, 2-4pm (NY time)
Room: Graduate Center Room 7395

Davide Sutto (Oslo).
Title: The iterative conception of pluralities

Abstract: Georg Cantor informally distinguished between “consistent” and “inconsistent” multiplicities as those many things that, respectively, can and cannot be thought of as one, i.e., as a set. In this talk I propose a framework that clarifies the distinction through a contemporary development of the iterative conception of set. Reshaping Tim Button’s Level Theory by means of plural logic, I define and axiomatize the notion of a plural level. This provides an explanation of Cantor’s consistent multiplicities as level-bound pluralities, namely as those pluralities that appear at some level of the plural cumulative hierarchy of sets. Furthermore, it also yields a development of set theory from plural logic that retains the full power of the comprehension axiom schema. This feature is especially relevant as it enables a parallel understanding of inconsistent multiplicities as those pluralities that are not level-bound, that is, as proper classes.

Logic and Metaphysics Workshop
Date: Monday, March 17, 4-6pm (NY time)
Room: Graduate Center Room 7395

Greg Restall (St Andrews).
Title: Modal logic and contingent existence

Abstract: In this talk, I will defend contingentism, the idea that some things exist contingently. It might be surprising that this needs defence, but natural reasoning principles concerning possibility and necessity on the one hand, and the existential and universal quantifiers on the other, have led some to necessitism, the view that everything that exists, exists necessarily. Almost all recent work on modal semantics makes essential use of possible worlds models. These models have proved useful for analysing the structural properties of modal logics, but it is less clear that they fix the meaning of our modal vocabulary, given that we have no grasp of what counts as a possible world, independent of our grasp of what counts as possible. In this talk, I describe an inferentialist semantics for modal and quantificational vocabulary, not as a rival to possible worlds models, but as an explanation of how the concepts we do employ can be modelled using possible worlds. I then use this inferentialist semantics to clarify the contingentist’s commitments, and offer answers to necessitist objections.

- - - - Tuesday, Mar 18, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 11, 10:30am (NY time), CUNY Graduate Center, Room: 4214.03

Scott Sets in algebraic settings
Alf Dolich CUNY

- - - - Wednesday, Mar 19, 2025 - - - -

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: Sophie d'Espalungue.
Date and Time: Wednesday March 19, 2025, 2:00 - 3:00 PM. Zoom talk. NOTE SPECIAL TIME!!
Title: Building All of Mathematics Without Axioms: An n-Categorical Manifesto.

- - - - Thursday, Mar 20, 2025 - - - -

- - - - Friday, Mar 21, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, March 21, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Tristan van der Vlugt, TU Wien
Meagre and Null Ideals for Uncountable Cardinals

We will consider the space of functions from to for various choices of and . In the first part of the talk we define topologies on such spaces and discuss the -meagre ideal (i.e. sets that are unions of -many nowhere dense sets), and their associated cardinal invariants. In the second part, we will look at various ways to consider (cardinal invariants of) the null ideal on such spaces.

Model Theory Seminar

CUNY Graduate Center
Friday, March 21, 12:30pm NY time, Room: 5417

Vince Guingona Towson University

Logic Workshop

CUNY Graduate Center
Friday, March 21, 2:00pm-3:30pm, Room 5417

Sheila Miller Edwards Arizona State University

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

UPDATE 4: This Week in Logic at CUNY

This Week in Logic at CUNY

3/13/2025 11:44:45

One more time - the correct Logic and Metaphysics speakers on 3/17 will be 2pm (Marian Călborean, Bucharest) and 4pm (Greg Restall, St Andrews), updated details below.

Jonas

ps. Apologies for the multitude of emails this week - I'm certainly resolved not to make any more errors, we'll see how that works for me :)

(The rest of) This Week in Logic at CUNY:

- - - - Thursday, Mar 13, 2025 - - - -

- - - - Friday, Mar 14, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, March 14, 12:30pm NY time, Room: 5417

A three body problem in stable (and simple and NSOP_1) theories
Alex Kruckman Wesleyan University

A few years ago, a problem arose in some of my work that I wasn’t able to solve, forcing me to add a technical hypothesis to a theorem - this has bothered me ever since. The issue has to do with the relationship between independence in a stable (or simple or NSOP_1) theory and independence in a stable reduct. In this rather informal talk, I will describe the problem and some partial results. The audience is welcome to provide proofs or counterexamples.

Logic Workshop
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417

Some pseudofinite rings and modules

Alex Kruckman Wesleyan University

Recall that a structure is pseudofinite if every sentence satisfied by that structure has a finite model - equivalently, if the structure is elementarily equivalent to an ultraproduct of finite structures. In this talk, I will present some work in progress from two independent projects around pseudofinite rings and pseudofinite modules: one is joint work with Alex Van Abel, the other is work of my PhD student Roberto Torres. These two projects are linked by the important role played by the class of von Neumann regular rings.

Next Week in Logic at CUNY:

- - - - Monday, Mar 17, 2025 - - - -

Logic and Metaphysics Workshop (NOTE BACK-TO-BACK TALKS TODAY)
Date: Monday, March 17, 2-4pm (NY time)
Room: Graduate Center Room 7395

Marian Călborean (Bucharest).
Title: Vagueness as dispersion

Abstract: Classical logic (FOL) is thought to be incompatible with the fuzzy cutoffs of vague predicates. I conceptualize vagueness as the dispersion of negative and positive cases of predicates such as “tall” across ranks defined by the preferred ordering—e.g., “having less or equal cm of height”. I distinguish vertical dispersion—both negative and positive cases of the predicate can share the same measurement—and horizontal dispersion—change happens with gradually fewer intercalations of negative and positive cases. Parallel to the non-classical approach of Cobreros et al. (2012), I introduce two classical shorthand modifiers “strictly” and “broadly”. Then, the Sorites paradox is solved by weakening the principle of tolerance to “If a person is strictly tall, anyone one less cm of height is broadly tall”, noted ∀xy.((Lxy ∧ [L]Ty) ⊃ Tx). This notational extension of FOL is conservative and can express higher-order vagueness.

Logic and Metaphysics Workshop
Date: Monday, March 17, 4-6pm (NY time)
Room: Graduate Center Room 7395

Greg Restall (St Andrews).
Title: Modal logic and contingent existence

Abstract: In this talk, I will defend contingentism, the idea that some things exist contingently. It might be surprising that this needs defence, but natural reasoning principles concerning possibility and necessity on the one hand, and the existential and universal quantifiers on the other, have led some to necessitism, the view that everything that exists, exists necessarily. Almost all recent work on modal semantics makes essential use of possible worlds models. These models have proved useful for analysing the structural properties of modal logics, but it is less clear that they fix the meaning of our modal vocabulary, given that we have no grasp of what counts as a possible world, independent of our grasp of what counts as possible. In this talk, I describe an inferentialist semantics for modal and quantificational vocabulary, not as a rival to possible worlds models, but as an explanation of how the concepts we do employ can be modelled using possible worlds. I then use this inferentialist semantics to clarify the contingentist’s commitments, and offer answers to necessitist objections.

- - - - Tuesday, Mar 18, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 11, 10:30am (NY time), CUNY Graduate Center, Room: 4214.03

Scott Sets in algebraic settings
Alf Dolich CUNY

- - - - Wednesday, Mar 19, 2025 - - - -

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: Sophie d'Espalungue.
Date and Time: Wednesday March 19, 2025, 2:00 - 3:00 PM. Zoom talk. NOTE SPECIAL TIME!!
Title: Building All of Mathematics Without Axioms: An n-Categorical Manifesto.

- - - - Thursday, Mar 20, 2025 - - - -

- - - - Friday, Mar 21, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, March 21, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Tristan van der Vlugt, TU Wien
Meagre and Null Ideals for Uncountable Cardinals

We will consider the space of functions from to for various choices of and . In the first part of the talk we define topologies on such spaces and discuss the -meagre ideal (i.e. sets that are unions of -many nowhere dense sets), and their associated cardinal invariants. In the second part, we will look at various ways to consider (cardinal invariants of) the null ideal on such spaces.

Model Theory Seminar

CUNY Graduate Center
Friday, March 21, 12:30pm NY time, Room: 5417

Vince Guingona Towson University

Logic Workshop

CUNY Graduate Center
Friday, March 21, 2:00pm-3:30pm, Room 5417

Sheila Miller Edwards Arizona State University

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

KGRC talks March 20

Kurt Godel Research Center

3/14/2025 7:24:59

KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, March 20, 11:30am--1:00pm, hybrid mode "The theory of symmetric systems and extensions III" J. Schilhan (U Wien) In this 3 talk series I will give an introduction to the technique of symmetric systems and present some of the recent results we have obtained joint with A. Ka9ragila. Symmetric systems produce so called symmetric extensions which are intermediate models between $V$ and forcing extension $V[G]$. These models may not satisfy the Axiom of Choice and their primary use is to obtain consistency results for $\mathsf{ZF}$. On the other hand, they are also useful in generally understanding and classifying intermediate models. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, March 20, 3:00pm--3:50pm, hybrid mode Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, March 20, 3:00pm--3:50pm, hybrid mode "Meagre and Null Ideals for Uncountable Cardinals" T. van der Vlugt (TU Wien) We will consider the space of functions from $\lambda$ to $\kappa$ for various choices of $\lambda$ and $\kappa$. In the first part of the talk we define topologies on such spaces and discuss the $\mu$-meagre ideal (i.e. sets that are unions of $\mu$-many nowhere dense sets) and their associated cardinal invariants. In the second part, we will look at various ways to look at (cardinal invariants of) the null ideal on such spaces. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recording available so far of the Set Theory Seminar: Mar 13: J. Schilhan (U Wien): "The theory of symmetric systems and extensions II" https://ucloud.univie.ac.at/index.php/s/aP24YCP62LFt3r7 Video recording available so far of the Logic Colloquium: Mar 13: M. Iannella (TU Wien): "Classification of 3-manifolds" https://ucloud.univie.ac.at/index.php/s/T3rbBSQBS7gB4Gr -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

3/16/2025 22:35:00

This Week in Logic at CUNY:

- - - - Monday, Mar 17, 2025 - - - -

Logic and Metaphysics Workshop (NOTE BACK-TO-BACK TALKS TODAY)
Date: Monday, March 17, 2-4pm (NY time)
Room: Graduate Center Room 7395

Marian Călborean (Bucharest).
Title: Vagueness as dispersion

Abstract: Classical logic (FOL) is thought to be incompatible with the fuzzy cutoffs of vague predicates. I conceptualize vagueness as the dispersion of negative and positive cases of predicates such as “tall” across ranks defined by the preferred ordering—e.g., “having less or equal cm of height”. I distinguish vertical dispersion—both negative and positive cases of the predicate can share the same measurement—and horizontal dispersion—change happens with gradually fewer intercalations of negative and positive cases. Parallel to the non-classical approach of Cobreros et al. (2012), I introduce two classical shorthand modifiers “strictly” and “broadly”. Then, the Sorites paradox is solved by weakening the principle of tolerance to “If a person is strictly tall, anyone one less cm of height is broadly tall”, noted ∀xy.((Lxy ∧ [L]Ty) ⊃ Tx). This notational extension of FOL is conservative and can express higher-order vagueness.

Logic and Metaphysics Workshop (NOTE BACK-TO-BACK TALKS TODAY)
Date: Monday, March 17, 4-6pm (NY time)
Room: Graduate Center Room 7395

Greg Restall (St Andrews).
Title: Modal logic and contingent existence

Abstract: In this talk, I will defend contingentism, the idea that some things exist contingently. It might be surprising that this needs defence, but natural reasoning principles concerning possibility and necessity on the one hand, and the existential and universal quantifiers on the other, have led some to necessitism, the view that everything that exists, exists necessarily. Almost all recent work on modal semantics makes essential use of possible worlds models. These models have proved useful for analysing the structural properties of modal logics, but it is less clear that they fix the meaning of our modal vocabulary, given that we have no grasp of what counts as a possible world, independent of our grasp of what counts as possible. In this talk, I describe an inferentialist semantics for modal and quantificational vocabulary, not as a rival to possible worlds models, but as an explanation of how the concepts we do employ can be modelled using possible worlds. I then use this inferentialist semantics to clarify the contingentist’s commitments, and offer answers to necessitist objections.

- - - - Tuesday, Mar 18, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 18, 10:30am (NY time), CUNY Graduate Center, Room: 4214.03

Scott Sets in algebraic settings
Alf Dolich CUNY

Computational Logic Seminar
Spring 2025 (in-person + zoom - for zoom link, please contact Sergei Artemov sartemov@gmail.com)

Tuesday, March 18, Time 2:00 - 4:00 PM, Graduate Center, rm. 3308
Speaker: Melvin Fitting, Graduate Center CUNY
Title: Semantic Tableaus II.

Abstract: Tableau systems are intuitively natural proof procedures, and have been formulated for quite a number of logics. Because of their inherent design, they serve well for proof discovery. The basic and most familiar tableau system is for classical logic, and I will begin with it. This will be followed by intuitionistic logic, and finally by several kinds of tableau systems for modal logics. I will also mention how the machinery can be adapted for some well-known non-classical many-valued logics. I will briefly discuss connections between tableau and sequent calculi. The presentation will be propositional. If there is time, I will sketch how quantification can be added, but that is really a topic in itself. The presentation is spread over two sessions.

- - - - Wednesday, Mar 19, 2025 - - - -

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: Sophie d'Espalungue.
Date and Time: Wednesday March 19, 2025, 2:00 - 3:00 PM. Zoom talk. NOTE SPECIAL TIME!!
Title: Building All of Mathematics Without Axioms: An n-Categorical Manifesto.

Abstract: The formalization of mathematical language traditionally relies on undefined terms - such as Set, Type, universes - whose properties are specified by axioms and inference rules. In this talk, I present an alternative approach in which mathematical language is entirely built from definitions. At its core are n-category constructors - an internal alternative to typing judgments - denoted as (X : Cat_n) for a variable X, which are inductively assigned a truth value - a meaning. Defining an n-category here consists of constructing an element (a proof) of the corresponding truth value. To give meaning to these constructors, (n-1)-categories and (n-1)-functors are inductively organised as an n-category, resulting in a graded structure of nested n-categories (Cat_{n-1} : Cat_n). By treating each mathematical object as an element of another object, this framework offers a natural and expressive language for higher category theory, set theory, and logic, all with vast generalisation potential. I will discuss key consequences of this approach, including its implications for fundamental notions such as sameness, size, and ∞-categories, as well as its connexions to homotopy type theory.

- - - - Thursday, Mar 20, 2025 - - - -

- - - - Friday, Mar 21, 2025 - - - -

Set Theory Seminar

CUNY Graduate Center
Friday, March 21, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Tristan van der Vlugt, TU Wien
Meagre and Null Ideals for Uncountable Cardinals

We will consider the space of functions from to for various choices of and . In the first part of the talk we define topologies on such spaces and discuss the -meagre ideal (i.e. sets that are unions of -many nowhere dense sets), and their associated cardinal invariants. In the second part, we will look at various ways to consider (cardinal invariants of) the null ideal on such spaces.

Model Theory Seminar

CUNY Graduate Center
Friday, March 21, 12:30pm NY time, Room: 5417

Vince Guingona Towson University
Statistical Learning and Model Theory

In this talk, I explore the connections between Statistical Learning Theory and Model Theory. This includes the connections between PAC-learning and NIP and the connections between differentially private PAC-learning and stability. Finally, I examine the work that my colleagues and I have started on improving the sample complexity of differentially private PAC-learning algorithms using techniques from stability theory. This work is joint with Alexei Kolesnikov, Miriam Parnes, and Natalie Piltoyan.

Logic Workshop

CUNY Graduate Center
Friday, March 21, 2:00pm-3:30pm, Room 5417

Sheila Miller Edwards Arizona State University

How to construct a free, two-generated left distributive algebra of elementary embeddings

The relationship between left distributivity and very large cardinal embeddings was discovered in the 1980s but remains, in many ways, mysterious. In the late 1980s Richard Laver showed that the closure of a single elementary embedding under the application operation generates a free left distributive algebra and demonstrated the linearity of a particular ordering on terms of the free left distributive algebra (given the existence of such embeddings). Patrick Dehornoy later used the braid group on infinitely many generators to show the linearity of that ordering relation within ZFC. (The consistency strength of other related theorems is still unknown). David Larue subsequently extended that work to demonstrate braid group representations of the free left distributive algebra on generators, for any natural number . Still elusive was an algebra of embeddings isomorphic to a free left distributive algebra on more than one generator. We present an inverse limit construction of such a free, two-generated left distributive algebra of embeddings from a slightly stronger large cardinal assumption than the one used by Laver. (Joint work with Andrew Brooke-Taylor and Scott Cramer.)

Next Week in Logic at CUNY:

- - - - Monday, Mar 24, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 24, 2-4pm (NY time)
Room: Graduate Center Room 7395

Davide Sutto (Oslo).
Title: The iterative conception of pluralities

Abstract: Georg Cantor informally distinguished between “consistent” and “inconsistent” multiplicities as those many things that, respectively, can and cannot be thought of as one, i.e., as a set. In this talk I propose a framework that clarifies the distinction through a contemporary development of the iterative conception of set. Reshaping Tim Button’s Level Theory by means of plural logic, I define and axiomatize the notion of a plural level. This provides an explanation of Cantor’s consistent multiplicities as level-bound pluralities, namely as those pluralities that appear at some level of the plural cumulative hierarchy of sets. Furthermore, it also yields a development of set theory from plural logic that retains the full power of the comprehension axiom schema. This feature is especially relevant as it enables a parallel understanding of inconsistent multiplicities as those pluralities that are not level-bound, that is, as proper classes.

Rutgers Logic Seminar
Monday March 24, 3:30pm, Rutgers University, Hill Center, Hill 705

Matthew Harrison-Trainor, UIC
Gaps in Scott spectra of theories

- - - - Tuesday, Mar 25, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 25, 1pm (NY time) Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Ermek Nurkhaidarov Penn State Mont Alto

- - - - Wednesday, Mar 26, 2025 - - - -

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: Hannah Aizenman, The Graduate Center, CUNY.

Date and Time: Wednesday March 26, 2025, 7:00 - 8:30 PM. IN-PERSON TALK!

Title: Topologically Equivalent Artist Model.

Abstract: The contract data visualization tools make with their users is that a chart is a faithful and accurate visual representation of the numbers it is made from. Motivated by wanting to make better tools, we propose a methodology for fully specifying arbitrary data to visualization mappings in a manner that easily translates to code. We propose that fiber bundles provide a uniform interface for describing a variety of underlying data - tables, images, networks, etc. - in a manner that independently encodes the mathematical structure of the topology and the fields of the dataset. Modeling the data structures that store the datasets as sheaves provides a method for specifying visualization methods that are designed to work regardless of how the dataset is stored - whether the data is on disk, distributed, or on demand. Specifying the visualization library components as natural transforms of sheaves means that the constraints that the component must satisfy to be structure preserving can be specified as the set of morphisms on the data and graphic sheaves, including the structure on the topology and fields of the data. Using category theory to formally express how visual elements are constructed means we can translate those expectations into code, which can then be used to enforce the expectation that a visualization tool is faithfully translating between numbers and charts.

- - - - Thursday, Mar 27, 2025 - - - -

- - - - Friday, Mar 28, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 28, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Stefan Hoffelner TU Wien
The global -Uniformization Property and

We show that, given a reflecting cardinal, one can generically produce a universe of in which additionally the -uniformization property holds for every simultaneously.

Logic Workshop

CUNY Graduate Center
Friday, March 28, 2:00pm-3:30pm, Room 5417
Aaron Anderson University of Pennsylvania

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

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

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71st Nankai Logic Colloquium

Nankai Logic Colloquium

3/17/2025 5:11:36

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Jenna Zomback from the University of Maryland, College Park. This talk will take place this Friday, March 21st, from 9am to 10am (UTC+8, Beijing time).

Title: Ergodic theorems, weak mixing, and chaining

Abstract: Several recent methods for proving pointwise ergodic theorems for pmp actions of free groups critically use weak mixing properties of Markov measures on the boundary of a free group of finite rank. However, it was not known exactly which Markov measures are weak mixing. In joint work with Anush Tserunyan, we give a complete characterization of such measures. It turns out that, under mild non-degeneracy assumptions, they are exactly the Markov measures arising from strictly irreducible transition matrices, a condition introduced by Bufetov in 2000 for a different purpose. The proof of this characterization goes through proving equivalences with a new combinatorial condition on the action that we call chaining.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 71st Nankai Logic Colloquium-- Jenna Zomback

Time: 9:00am, Mar. 21, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=99666015030

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Wednesday seminar

Prague Set Theory Seminar

3/17/2025 8:59:07

Dear all, There will be no seminar this week Wednesday March 19th. (Lack of speakers and absence of some regular participants.) The seminar will meet again next week, Wednesday March 26th for a talk of Shujie Yang. Best, David

Logic Seminar 26 March 2025 17:00 hrs by Chong Chi Tat

NUS Logic Seminar

3/19/2025 22:51:03

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 26 March 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Chong Chi Tat Title: Definable solutions of combinatorial principles. Abstract: Combinatorial principles is a prominent area of investigation in reverse mathematics. The computational complexity of a solution of an instance of a principle began with Jockusch work (1972) on Ramsey's theorem over the standard model of Peano arithmetic. In general, every instance of a combinatorial principle has a definable solution over the standard model. For an arbitrary model of RCA_0, however, the situation is not clear. There exist weak models and instances of combinatorial principles (such as Ramsey's theorem for pairs) for which no definable solution is known. In this talk we present an analysis of the problem of definable solutions and some nonexistence results. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar

3/20/2025 5:43:40

Dear all, The seminar meets on Wednesday March 26th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Shujie Yang -- Projective Fraïssé Limits of Rooted Tree We will discuss the application of projective Fraïssé theory to finite rooted trees. By focusing on specific classes of epimorphisms between these structures, we construct projective Fraïssé limits that give rise to interesting continua, including the Mohler-Nikiel universal dendroid, the Ważewski dendrite, and others. We will also present our current partial results on the Ramsey property of certain classes. The Kechris-Pestov-Todorcevic (KPT) correspondence allows us to determine the universal minimal flow of automorphism groups of continua. This talk is based on joint work with W. Charatonik, A. Kwiatkowska, and R. Roe. Best, David

KGRC Set Theory talk March 27

Kurt Godel Research Center

3/21/2025 7:34:23

KGRC/Institute of Mathematics invites you to the following talk: (updates at https://kgrc.univie.ac.at/eventsnews/) * * * * * * * * * Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, March 27, 11:30am--1:00pm, hybrid mode "Amalgamation, Axiom of Choice and Euclidean geometry I" A. Fatalini (U Münster, DE) We will show that there is a model of ${\rm ZF}$ with no well-order on the reals in which there is a partition of $\mathbb{R}^3$ in unit circles. The major obstacle is satisfying some amalgamation, for which geometrical and algebraic considerations are needed. If time allows, we will see how these techniques can generalize to other applications. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recording available so far from the Set Theory Seminar: Mar 20: J. Schilhan (U Wien): "The theory of symmetric systems and extensions III". https://ucloud.univie.ac.at/index.php/s/Y674oxd4qDEjXTa Video recording available so far from the Logic Colloquium: Mar 20: T. van der Vlugt (TU Wien): "Meagre and Null Ideals for Uncountable Cardinals". https://ucloud.univie.ac.at/index.php/s/sYbfGoS3XTdKx5t -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

3/23/2025 22:36:00

This Week in Logic at CUNY:

- - - - Monday, Mar 24, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 24, 2-4pm (NY time)
Room: Graduate Center Room 7395

Davide Sutto (Oslo).
Title: The iterative conception of pluralities

Abstract: Georg Cantor informally distinguished between “consistent” and “inconsistent” multiplicities as those many things that, respectively, can and cannot be thought of as one, i.e., as a set. In this talk I propose a framework that clarifies the distinction through a contemporary development of the iterative conception of set. Reshaping Tim Button’s Level Theory by means of plural logic, I define and axiomatize the notion of a plural level. This provides an explanation of Cantor’s consistent multiplicities as level-bound pluralities, namely as those pluralities that appear at some level of the plural cumulative hierarchy of sets. Furthermore, it also yields a development of set theory from plural logic that retains the full power of the comprehension axiom schema. This feature is especially relevant as it enables a parallel understanding of inconsistent multiplicities as those pluralities that are not level-bound, that is, as proper classes.

Rutgers Logic Seminar
Monday March 24, 3:30pm, Rutgers University, Hill Center, Hill 705

Matthew Harrison-Trainor, UIC
Gaps in Scott spectra of theories

- - - - Tuesday, Mar 25, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, March 25, 1pm (NY time) Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Ermek Nurkhaidarov Penn State Mont Alto

Automorphisms of countable short recursively saturated models of PA

In this talk we discuss automorphisms of countable short recursively saturated models of PA.

Kossak-Schmerl 95 shows that: if M is a countable, arithmetically saturated model of PA, then the automorphism group of M codes its standard system. We discuss how to prove a similar result for countable short arithmetically saturated models of PA.

This is joint work with Erez Shochat.

Computational Logic Seminar
Spring 2025 (in-person + zoom - for zoom link, please contact Sergei Artemov sartemov@gmail.com)
Tuesday, March 25, Time 2:00 - 4:00 PM, Graduate Center, rm. 3308
Speaker: Igor Sedlár, Institute of Computer Science, Czech Academy of Sciences
Title: Probability and Modality: A Many-valued Approach

Abstract: Probabilistic logics have been studied and applied in various fields for decades. On the many-valued approach to probabilistic logic, due to Petr Hájek and collaborators, a statement of the form "A is probable" is seen as an imprecise statement whose truth degree is identified with the probability of A. In turn, formulas of a many-valued probabilistic logic express imprecise statements about probabilities, such as "A is much less probable than B" etc. This contrasts with the classical approach, centred on the work of Ronald Fagin and Joseph Halpern, where statements about probability are precise statements - always true or false - expressed by linear inequalities comparing probabilities of events with certain thresholds.

In computer science, artificial intelligence and economics, modal probabilistic logics are of particular importance. These logics formalise reasoning about probability in the presence of modal notions such as knowledge, belief, time and action. In this talk, I outline a many-valued approach to modal probabilistic logic. This approach provides a unique model that combines probability with qualitative uncertainty. For example, modal operators in the many-valued setting can express upper and lower probability envelopes of sets of probabilities. The main technical results I will report on are reductions of modal many-valued probabilistic logics to many-valued modal logics, and complexity results for various modal many-valued probabilistic logics. The talk is based on joint work with Ondrej Majer (Czech Academy of Sciences) and Daniil Kozhemiachenko (Aix-Marseille Université).

- - - - Wednesday, Mar 26, 2025 - - - -

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: Hannah Aizenman, The Graduate Center, CUNY.

Date and Time: Wednesday March 26, 2025, 7:00 - 8:30 PM. IN-PERSON TALK!

Title: Topologically Equivalent Artist Model.

Abstract: The contract data visualization tools make with their users is that a chart is a faithful and accurate visual representation of the numbers it is made from. Motivated by wanting to make better tools, we propose a methodology for fully specifying arbitrary data to visualization mappings in a manner that easily translates to code. We propose that fiber bundles provide a uniform interface for describing a variety of underlying data - tables, images, networks, etc. - in a manner that independently encodes the mathematical structure of the topology and the fields of the dataset. Modeling the data structures that store the datasets as sheaves provides a method for specifying visualization methods that are designed to work regardless of how the dataset is stored - whether the data is on disk, distributed, or on demand. Specifying the visualization library components as natural transforms of sheaves means that the constraints that the component must satisfy to be structure preserving can be specified as the set of morphisms on the data and graphic sheaves, including the structure on the topology and fields of the data. Using category theory to formally express how visual elements are constructed means we can translate those expectations into code, which can then be used to enforce the expectation that a visualization tool is faithfully translating between numbers and charts.

- - - - Thursday, Mar 27, 2025 - - - -

- - - - Friday, Mar 28, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, March 28, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Stefan Hoffelner TU Wien
The global -Uniformization Property and

We show that, given a reflecting cardinal, one can generically produce a universe of in which additionally the -uniformization property holds for every simultaneously.

Logic Workshop

CUNY Graduate Center
Friday, March 28, 2:00pm-3:30pm, Room 5417

Aaron Anderson, University of Pennsylvania

Examples of Distal Metric Structures

We identify several examples of distal metric structures and examine several consequences of distality, such as the existence of distal cell decompositions, in each. These results include joint work with Itaï Ben Yaacov and with Diego Bejarano. One class of examples starts with finding a metric structure whose automorphism group is the group of increasing homeomorphisms of the unit interval. We will discuss some properties of this structure and extrapolate to other models of its theory, which we call 'dual linear continua.' Another source of examples includes real closed metric valued fields. These give rise to a notion of ordered metric structure, providing a viewpoint to study o-minimality in continuous logic.

Next Week in Logic at CUNY:

- - - - Monday, Mar 31, 2025 - - - -

Rutgers Logic Seminar
Monday March 31, 3:30pm, Rutgers University, Hill Center, Hill 705

Aaron Anderson, U Penn
Examples of Distal Metric Structures

- - - - Tuesday, Apr 1, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, April 1, 1pm (NY time) Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Erez Shochat St. Francis College

- - - - Wednesday, Apr 2, 2025 - - - -

- - - - Thursday, Apr 3, 2025 - - - -

- - - - Friday, Apr 4, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 4, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Siiri Kivimäki University of Helsinki

Logic Workshop

CUNY Graduate Center
Friday, April 4, 2:00pm-3:30pm, Room 5417

Valentina Harizanov George Washington University

- - - - Other Logic News - - - -

There are a number of upcoming meetings of the Mid-Atlantic Mathematical Logic Seminar (MAMLS), listed below.

Overview/MAMLS home page: https://nylogic.github.io/MAMLS.html

NERDS 26.0 (New England Recursion and Definability Seminar)

Date: April 5–6, 2025
Place: University of Connecticut, Hartford

Meeting details: The meeting will be co-located with the AMS Special Session on Computability Theory at the Spring 2025 AMS Eastern Sectional Meeting, which will be held in Hartford, CT, April 5-6, 2025 (Saturday-Sunday). For full details, including full schedule, directions, parking, etc., please consult the official AMS page.

Northeast Model Theory Day
Saturday, April 5, 2025, 9am-6pm
Towson University, Towson, Maryland

Details can be found on our website: https://nemtd.wescreates.wesleyan.edu/

All are welcome to attend. For planning purposes, we would appreciate it if you would register.

GlaD (Groups, Logic, and Dynamics) meeting

Saturday, April 12

Rutgers University, New Brunswick.

This is the third installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.

Limited funding for junior and local participants are available. Please contact the organizers to apply and check availability.
https://sites.math.rutgers.edu/~fc327/GLaDS2025/index.html

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

72nd Nankai Logic Colloquium

Nankai Logic Colloquium

3/24/2025 7:31:32

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon at an unusual time. Our speaker this week will be Shichang Song from Beijing Jiaotong Univerisity. This talk will take place this Friday, March 28th, from 2pm to 3pm (UTC+8, Beijing time).

Title: Borel completeness of the class of countable Steiner triple systems

Abstract: In this talk, we show that the isomorphism relation for the class of countable Steiner triple systems is Borel complete, that is, the isomorphism relation for arbitrary countable structures is Borel reducible to that for countable Steiner triple systems. To prove it, we construct a faithful Borel reduction from countable graphs to countable Steiner triple systems. Moreover, we prove that such reduction also preserves automorphisms. This is joint work with Guangyin Ma.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 72nd Nankai Logic Colloquium-- Shichang Song Time: 14:00pm, Mar. 28, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=97121839851

_____________________________________________________________________________________________________________________________________________________

There is no Nankai Logic Colloquium next week (April 4th) in observance of the Memorial Day holidays.

Best regards,

Wei

KGRC Set Theory talks April 3

Kurt Godel Research Center

3/28/2025 5:35:00

KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, April 3, 11:30am--1:00pm, hybrid mode "Amalgamation, Axiom of Choice and Euclidean geometry II" A. Lihuen Fatalini (U Münster, DE) This is part 2 of a 2 talk series (part 1: https://kgrc.univie.ac.at/eventsnews/event-details/news/amalgamation-axiom-of-choice-and-euclidean-geometry-i/). We will show that there is a model of ${\rm ZF}$ with no well-order on the reals in which there is a partition of $\mathbb{R}^3$ in unit circles. The major obstacle is satisfying some amalgamation, for which geometrical and algebraic considerations are needed. If time allows, we will see how these techniques can generalize to other applications. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, April 3, 3:00pm--3:50pm, hybrid mode "Paradoxical sets and the Axiom of Choice" A. Lihuen Fatalini (U Münster, DE) There are many “paradoxical sets” of reals that can be obtained using a well-ordering of the reals, which is a consequence of the Axiom of Choice. In ${\rm ZF}$, can we recover the well-ordering of the reals from the existence of a given paradoxical set? Under certain conditions of Extendability and Amalgamation, we give a negative answer to this question. In particular, we solve it for the paradoxical set given by a partition of $\mathbb{R}^3$ in unit circles. For this, some geometrical and algebraic considerations are needed. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recording available so far from the Set Theory Seminar: Mar 27: A. Lihuen Fatalini (U Münster, DE): "Amalgamation, Axiom of Choice and Euclidean geometry I" https://ucloud.univie.ac.at/index.php/s/PTsWGxtdDdmD8o5 . -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

Wednesday seminar

Prague Set Theory Seminar

3/30/2025 4:33:42

Dear all, The seminar meets on Wednesday April 2nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Rob Sullivan -- Ultrahomogeneous oriented graphs, canonical amalgamation and universal automorphism groups There is a full classification of all countable ultrahomogeneous oriented graphs, published by Cherlin in the late nineties. We will take a (mildly personalised, and hopefully relaxed) tour of this classification, discussing whether each oriented graph therein has a notion of canonical amalgamation, and whether it has a universal automorphism group. This is joint work with A. Kwiatkowska and J. Winkel. Best, David

This Week in Logic at CUNY

3/30/2025 22:31:00

This Week in Logic at CUNY:

- - - - Monday, Mar 31, 2025 - - - -

Rutgers Logic Seminar
Monday March 31, 3:30pm, Rutgers University, Hill Center, Hill 705

Aaron Anderson, U Penn
Examples of Distal Metric Structures

- - - - Tuesday, Apr 1, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, April 1, 1pm (NY time) Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Erez Shochat, St. Francis College

Invariant Cuts of Countable Short Recursively Saturated Models of PA

In this talk we continue the discussion on the automorphism groups of countable short recursively saturated models of PA. In particular, we discuss the cuts of the model which are fixed setwise by all automorphisms (invariant cuts). We show that such cuts occur in different places of the model, depending on the types realized in the last gap. We then show that this implies, in some of these cases, that the automorphism groups of such models are non-isomorphic as topological groups. This is a joint work with Ermek Nurkhaidarov.

- - - - Wednesday, Apr 2, 2025 - - - -

- - - - Thursday, Apr 3, 2025 - - - -

- - - - Friday, Apr 4, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 4, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Siiri Kivimäki University of Helsinki

Logic Workshop

CUNY Graduate Center
Friday, April 4, 2:00pm-3:30pm, Room 5417

Valentina Harizanov, George Washington University
Computable structures and their effective products

We consider a computability-theoretic version of the ultraproduct construction for an infinite uniformly computable sequence of structures, where the role of an ultrafilter is played by an infinite set of natural numbers that cannot be split into two infinite subsets by any computably enumerable set. For computable structures, effective powers preserve only the first-order sentences of lower levels of quantifier complexity. Additional decidability of the structure increases preservation of the fragments of its theory in an effective power, so that a structure with a computable elementary diagram is elementarily equivalent to its effective power. We will present a number of recent collaborative results.

Next Week in Logic at CUNY:

- - - - Monday, Apr 7, 2025 - - - -

Rutgers Logic Seminar
Monday April 7, 3:30pm, Rutgers University, Hill Center, Hill 705

Tan Ozalp, Notre Dame

Logic and Metaphysics Workshop
Date: Monday, April 4/7, 2-4pm (NY time)
Room: Graduate Center Room 7395

Allison Aitken (Columbia).
Title: Vasubandhu on intentional action: From mind-body to mind-only

Abstract: Jonathan Schaffer argues that mereological nihilism “culminates in monism.” In other words, the same sorts of parsimony considerations that motivate the rejection of real composites ultimately lead to a monist ontology. In this talk, I show how the 4th-5th century Buddhist philosopher Vasubandhu makes a similar argument, but instead of proposing an existence monism, as Schaffer does, Vasubandhu advances a type-monism–specifically, a form of metaphysical idealism on which all that exist are mental representations. I show how he exploits challenges confronting mereological nihilists when it comes to accommodating intentional action in their ontologies in order to call into question the explanatory utility of matter itself. He first uses puzzles concerning the metaphysics and causal mechanics of action to eliminatively reduce bodily action to mental action, and then leverages the same principle of parsimony that motivates his external world realist interlocutors to exclude real composites from their ontology to jettison matter from the picture altogether. I consider reasons why Vasubandhu resists existence monism and instead takes his type-monism to be the simplest sufficient ontology capable of explaining the sorts of things that matter most to him and his fellow-Buddhists, like intentional actions that are both morally significant and causally efficacious.

- - - - Tuesday, Apr 8, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, April 8, 1pm (NY time) Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Daniel Isaacson, Oxford University
Consideration of Dummett's claim that the meaning of 'natural number' is inherently vague

I shall expound Michael Dummett's claim in his paper, 'The philosophical significance of Gödel's theorem' (1963), and in later writings, that a consequence of the indefinite extensibility of Gödel incompleteness is that 'the meaning of 'natural number' is inherently vague'. Though of course Gödel incompleteness establishes that every formal system containing basic arithmetic has a proper extension, I claim, against Dummett's view, that there is a notion of arithmetical truth intrinsic to the meaning of 'natural number' which is stable, not indefinitely extensible, and that first-order Peano Arithmetic is sound and complete with respect to that notion of arithmetical truth. Thereby the meaning of 'natural number' is not vague but clear and precise.

- - - - Wednesday, Apr 9, 2025 - - - -

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: Emilio Minichiello, CUNY CityTech.

Date and Time: Wednesday April 9, 2025, 7:00 - 8:30 PM. IN PERSON TALK.

Title: Structured Decomposition Categories.

Abstract: In this talk I’ll report on some new work, joint with Ben Bumpus, Zoltan Kocsis and Jade Master. The idea here is to come up with a categorical framework to talk about decompositions. In graph theory, there are all kinds of ways of decomposing graphs, the most important being tree decompositions. This is a way to decompose a graph into pieces in such a way that if you squint at it, it looks like a tree. By looking at the biggest piece and minimizing over all tree decompositions, one obtains treewidth, the most important graph invariant in algorithmics. In this paper, we abstract this notion, coming up with the definition of structured decomposition categories. To each such category, we can assign to each of its objects a width number. We prove that this number is monotone under monomorphisms, and come up with an appropriate definition of structured decomposition functor such that we get a relationship between widths. We construct several examples of structured decomposition categories, whose widths coincide with several important examples from the literature.

- - - - Thursday, Apr 10, 2025 - - - -

- - - - Friday, Apr 11, 2025 - - - -

*** CUNY Graduate Center Spring Recess 4/12-4/20 ***

- - - - Other Logic News - - - -

There are a number of upcoming meetings of the Mid-Atlantic Mathematical Logic Seminar (MAMLS), listed below.

Overview/MAMLS home page: https://nylogic.github.io/MAMLS.html

NERDS 26.0 (New England Recursion and Definability Seminar)

Date: April 5–6, 2025
Place: University of Connecticut, Hartford

Meeting details: The meeting will be co-located with the AMS Special Session on Computability Theory at the Spring 2025 AMS Eastern Sectional Meeting, which will be held in Hartford, CT, April 5-6, 2025 (Saturday-Sunday). For full details, including full schedule, directions, parking, etc., please consult the official AMS page.

Northeast Model Theory Day
Saturday, April 5, 2025, 9am-6pm
Towson University, Towson, Maryland

Details can be found on our website: https://nemtd.wescreates.wesleyan.edu/

All are welcome to attend. For planning purposes, we would appreciate it if you would register.

GlaD (Groups, Logic, and Dynamics) meeting

Saturday, April 12

Rutgers University, New Brunswick.

This is the third installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.

Limited funding for junior and local participants are available. Please contact the organizers to apply and check availability.
https://sites.math.rutgers.edu/~fc327/GLaDS2025/index.html

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY

3/31/2025 22:05:22

Hi everyone,

Note the addition of tomorrow's talk by Stipe Pandzic (LUCI Lab, University of Milan) in the Computational Logic Seminar.

Best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Mar 31, 2025 - - - -

Rutgers Logic Seminar
Monday March 31, 3:30pm, Rutgers University, Hill Center, Hill 705

Aaron Anderson, U Penn
Examples of Distal Metric Structures

- - - - Tuesday, Apr 1, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, April 1, 1pm (NY time) Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Erez Shochat, St. Francis College

Invariant Cuts of Countable Short Recursively Saturated Models of PA

In this talk we continue the discussion on the automorphism groups of countable short recursively saturated models of PA. In particular, we discuss the cuts of the model which are fixed setwise by all automorphisms (invariant cuts). We show that such cuts occur in different places of the model, depending on the types realized in the last gap. We then show that this implies, in some of these cases, that the automorphism groups of such models are non-isomorphic as topological groups. This is a joint work with Ermek Nurkhaidarov.

Computational Logic Seminar
Spring 2025 (in-person + zoom - for zoom link, please contact Sergei Artemov sartemov@gmail.com)
Tuesday, April 1, Time 2:00 - 4:00 PM, Graduate Center, rm. 3308
Speaker: Stipe Pandzic (LUCI Lab, University of Milan)
Title: Toward default justification logic for neuro-symbolic integration

Abstract: In this talk, I overview a justification logic-based (JL-based) framework unifying numerical learning and symbolic reasoning. I begin by introducing default JL as an explicit non-monotonic reasoning system that resolves challenges in defeasible argumentation. Its expressive syntax captures argumentative attacks—rebuttal, undercut, and undermining—directly in its object language, outperforming traditional 'argumentation frameworks' and other non-monotonic logics. Examples will illustrate how default JL excels in scenarios where defeasibility is central.

The second part starts from a long-standing challenge: integrating gradual valuations into non-monotonic systems for neuro-symbolic architectures. I present a method to embed numerical reasoning into JL, enabling us to weigh argument strength (reasons pro and contra). JL’s core operations—application and sum—gain a natural numerical, non-monotonic interpretation, refining the logical consequence of default JL. Finally, I argue that a non-monotonic variant of first-order justification logic is needed to fully connect default JL with inductive learning, echoing motivations behind Reiter’s default logic based on first-order logic.

- - - - Wednesday, Apr 2, 2025 - - - -

- - - - Thursday, Apr 3, 2025 - - - -

- - - - Friday, Apr 4, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 4, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Siiri Kivimäki University of Helsinki

Logic Workshop

CUNY Graduate Center
Friday, April 4, 2:00pm-3:30pm, Room 5417

Valentina Harizanov, George Washington University
Computable structures and their effective products

We consider a computability-theoretic version of the ultraproduct construction for an infinite uniformly computable sequence of structures, where the role of an ultrafilter is played by an infinite set of natural numbers that cannot be split into two infinite subsets by any computably enumerable set. For computable structures, effective powers preserve only the first-order sentences of lower levels of quantifier complexity. Additional decidability of the structure increases preservation of the fragments of its theory in an effective power, so that a structure with a computable elementary diagram is elementarily equivalent to its effective power. We will present a number of recent collaborative results.

Next Week in Logic at CUNY:

- - - - Monday, Apr 7, 2025 - - - -

Rutgers Logic Seminar
Monday April 7, 3:30pm, Rutgers University, Hill Center, Hill 705

Tan Ozalp, Notre Dame

Logic and Metaphysics Workshop
Date: Monday, April 4/7, 2-4pm (NY time)
Room: Graduate Center Room 7395

Allison Aitken (Columbia).
Title: Vasubandhu on intentional action: From mind-body to mind-only

Abstract: Jonathan Schaffer argues that mereological nihilism “culminates in monism.” In other words, the same sorts of parsimony considerations that motivate the rejection of real composites ultimately lead to a monist ontology. In this talk, I show how the 4th-5th century Buddhist philosopher Vasubandhu makes a similar argument, but instead of proposing an existence monism, as Schaffer does, Vasubandhu advances a type-monism–specifically, a form of metaphysical idealism on which all that exist are mental representations. I show how he exploits challenges confronting mereological nihilists when it comes to accommodating intentional action in their ontologies in order to call into question the explanatory utility of matter itself. He first uses puzzles concerning the metaphysics and causal mechanics of action to eliminatively reduce bodily action to mental action, and then leverages the same principle of parsimony that motivates his external world realist interlocutors to exclude real composites from their ontology to jettison matter from the picture altogether. I consider reasons why Vasubandhu resists existence monism and instead takes his type-monism to be the simplest sufficient ontology capable of explaining the sorts of things that matter most to him and his fellow-Buddhists, like intentional actions that are both morally significant and causally efficacious.

- - - - Tuesday, Apr 8, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, April 8, 1pm (NY time) Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Daniel Isaacson, Oxford University
Consideration of Dummett's claim that the meaning of 'natural number' is inherently vague

I shall expound Michael Dummett's claim in his paper, 'The philosophical significance of Gödel's theorem' (1963), and in later writings, that a consequence of the indefinite extensibility of Gödel incompleteness is that 'the meaning of 'natural number' is inherently vague'. Though of course Gödel incompleteness establishes that every formal system containing basic arithmetic has a proper extension, I claim, against Dummett's view, that there is a notion of arithmetical truth intrinsic to the meaning of 'natural number' which is stable, not indefinitely extensible, and that first-order Peano Arithmetic is sound and complete with respect to that notion of arithmetical truth. Thereby the meaning of 'natural number' is not vague but clear and precise.

- - - - Wednesday, Apr 9, 2025 - - - -

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: Emilio Minichiello, CUNY CityTech.

Date and Time: Wednesday April 9, 2025, 7:00 - 8:30 PM. IN PERSON TALK.

Title: Structured Decomposition Categories.

Abstract: In this talk I’ll report on some new work, joint with Ben Bumpus, Zoltan Kocsis and Jade Master. The idea here is to come up with a categorical framework to talk about decompositions. In graph theory, there are all kinds of ways of decomposing graphs, the most important being tree decompositions. This is a way to decompose a graph into pieces in such a way that if you squint at it, it looks like a tree. By looking at the biggest piece and minimizing over all tree decompositions, one obtains treewidth, the most important graph invariant in algorithmics. In this paper, we abstract this notion, coming up with the definition of structured decomposition categories. To each such category, we can assign to each of its objects a width number. We prove that this number is monotone under monomorphisms, and come up with an appropriate definition of structured decomposition functor such that we get a relationship between widths. We construct several examples of structured decomposition categories, whose widths coincide with several important examples from the literature.

- - - - Thursday, Apr 10, 2025 - - - -

- - - - Friday, Apr 11, 2025 - - - -

*** CUNY Graduate Center Spring Recess 4/12-4/20 ***

- - - - Other Logic News - - - -

There are a number of upcoming meetings of the Mid-Atlantic Mathematical Logic Seminar (MAMLS), listed below.

Overview/MAMLS home page: https://nylogic.github.io/MAMLS.html

NERDS 26.0 (New England Recursion and Definability Seminar)

Date: April 5–6, 2025
Place: University of Connecticut, Hartford

Meeting details: The meeting will be co-located with the AMS Special Session on Computability Theory at the Spring 2025 AMS Eastern Sectional Meeting, which will be held in Hartford, CT, April 5-6, 2025 (Saturday-Sunday). For full details, including full schedule, directions, parking, etc., please consult the official AMS page.

Northeast Model Theory Day
Saturday, April 5, 2025, 9am-6pm
Towson University, Towson, Maryland

Details can be found on our website: https://nemtd.wescreates.wesleyan.edu/

All are welcome to attend. For planning purposes, we would appreciate it if you would register.

GlaD (Groups, Logic, and Dynamics) meeting

Saturday, April 12

Rutgers University, New Brunswick.

This is the third installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.

Limited funding for junior and local participants are available. Please contact the organizers to apply and check availability.
https://sites.math.rutgers.edu/~fc327/GLaDS2025/index.html

- - - - Web Site - - - -

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

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Logic Seminar 2 April 2025 17:00 hrs at NUS by Jia Zekun

NUS Logic Seminar

4/1/2025 8:21:41

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 2 April 2025, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Jia Zekun Title: The Reverse Strength of the Existence of Eta-Maximal Sets Abstract: Post's problem is one of the most fundamental questions in the early development of recursion theory. In 1944, Post proved the existence of a non-recursive m-incomplete r.e. set and generalized his result to tt-reducibility and Q-reducibility. However, it seemed hopeless to further extend Post's technique to T-reducibility, and this problem remained open for a decade until it was solved in the affirmative by Friedberg and Muchnik independently. Surprisingly, Post's method was revived from a series of works by Malcev, Ershov, Marchenkov and Degtev in the 1970s. By introducing an underlying r.e. equivalence relation eta over the natural numbers, they showed that Post's problem could indeed be solved in Post's way. A key concept in the proof is the so-called eta-maximal set, resembling Post's idea of a maximal set. Although Chong and Yang proved that the existence of a maximal set is equivalent to ISigma_2 over PA- + BSigma_2, Downey conjectured that the existence of an eta-maximal set may be simpler despite their similarities in definition. In this talk, we will improve Degtev's construction of an eta-maximal set and show that Downey is right: PA- + ISigma_1 is enough to carry out and verify the construction. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

No Nankai Logic Colloquium this week

Nankai Logic Colloquium

4/2/2025 21:26:37

Hello everyone,

Due to holidays in China, there is no Nankai Logic Colloquium talk this week. We will resume our regular schedule next week on April 11.

Thank you for your understanding!

Best regards,

Wei

Wednesday seminar

Prague Set Theory Seminar

4/3/2025 4:38:13

Dear all, The seminar meets on Wednesday April 9th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Monroe Eskew -- Blob forcing We present a general framework for amalgamating many forcings that somehow generically stacks them rather than explicitly iterating in a sequence. This leads to a consistency proof of MM that avoids the theory of RCS iterations. There should be more applications, but this work is still in the early stages. It is joint with Curial Rodriguez. Best, David

KGRC Set Theory talk April 10

Kurt Godel Research Center

4/4/2025 5:29:52

KGRC/Institute of Mathematics invites you to the following talk: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, April 10, 11:30am--1:00pm, hybrid mode "Hyperfiniteness on topological Ramsey spaces" B. Bursics (Eötvös Loránd U, Budapest, HU) A central goal in the area of countable Borel equivalence relations (CBERs) is understanding hyperfinite CBERs. So far, roughly speaking, all known proofs for non-hyperfiniteness use measures, while the tool of Baire category is not useful in this context, as all CBERs are hyperfinite on a co-meager invariant set. Regarding topological Ramsey spaces (in the sense of Todorčević, a classical result of Mathias and Soare states that every CBER on the Ellentuck space $[{\mathbb N}]^{\mathbb N}$ is hyperfinite on a Ramsey positive set. There are similar results for certain other topological Ramsey spaces: Kanovei, Sabok and Zapletal proved the analogous canonization result for the Milliken space, and recently, Panagiotopulos and Wang showed that CBERs are hyperfinite (in fact, even smooth) on positive sets in the Carlson-Simpson space. We generalize these statements to all topological Ramsey spaces. This is joint work with Zoltán Vidnyánszky. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recording available so far from the Set Theory Seminar: Apr 3: A. Lihuen Fatalini (U Münster, DE): "Amalgamation, Axiom of Choice and Euclidean geometry II" https://ucloud.univie.ac.at/index.php/s/dbQtxqnYo6mtQs4 Video recording available so far from the Logic Colloquium: Apr 3: A. Lihuen Fatalini (U Münster, DE): "Paradoxical sets and the Axiom of Choice" https://ucloud.univie.ac.at/index.php/s/ESe4A4SirW892Y9 -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

4/6/2025 22:30:00

Hi everyone,

Heads up, I won't be sending out an email next Sunday 4/13 as CUNY is on Spring Break. We'll return the following Sunday 4/20.

Enjoy the break,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Apr 7, 2025 - - - -

Rutgers Logic Seminar
Monday April 7, 3:30pm, Rutgers University, Hill Center, Hill 705

Tan Ozalp, Notre Dame

Logic and Metaphysics Workshop
Date: Monday, April 4/7, 2-4pm (NY time)
Room: Graduate Center Room 7395

Allison Aitken (Columbia).
Title: Vasubandhu on intentional action: From mind-body to mind-only

Abstract: Jonathan Schaffer argues that mereological nihilism “culminates in monism.” In other words, the same sorts of parsimony considerations that motivate the rejection of real composites ultimately lead to a monist ontology. In this talk, I show how the 4th-5th century Buddhist philosopher Vasubandhu makes a similar argument, but instead of proposing an existence monism, as Schaffer does, Vasubandhu advances a type-monism–specifically, a form of metaphysical idealism on which all that exist are mental representations. I show how he exploits challenges confronting mereological nihilists when it comes to accommodating intentional action in their ontologies in order to call into question the explanatory utility of matter itself. He first uses puzzles concerning the metaphysics and causal mechanics of action to eliminatively reduce bodily action to mental action, and then leverages the same principle of parsimony that motivates his external world realist interlocutors to exclude real composites from their ontology to jettison matter from the picture altogether. I consider reasons why Vasubandhu resists existence monism and instead takes his type-monism to be the simplest sufficient ontology capable of explaining the sorts of things that matter most to him and his fellow-Buddhists, like intentional actions that are both morally significant and causally efficacious.

- - - - Tuesday, Apr 8, 2025 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, April 8, 1pm (NY time) Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Daniel Isaacson, Oxford University
Consideration of Dummett's claim that the meaning of 'natural number' is inherently vague

I shall expound Michael Dummett's claim in his paper, 'The philosophical significance of Gödel's theorem' (1963), and in later writings, that a consequence of the indefinite extensibility of Gödel incompleteness is that 'the meaning of 'natural number' is inherently vague'. Though of course Gödel incompleteness establishes that every formal system containing basic arithmetic has a proper extension, I claim, against Dummett's view, that there is a notion of arithmetical truth intrinsic to the meaning of 'natural number' which is stable, not indefinitely extensible, and that first-order Peano Arithmetic is sound and complete with respect to that notion of arithmetical truth. Thereby the meaning of 'natural number' is not vague but clear and precise.

Computational Logic Seminar

Spring 2025 (in-person + zoom - for zoom link, please contact Sergei Artemov sartemov@gmail.com)

Tuesday, April 8, Time 2:00 - 4:00 PM , Graduate Center, rm. 3308

Speaker: Thomas Ferguson, Rensselaer Polytechnic Institute

Title: A Family of Epistemic Logics of Zero Knowledge Proof

Abstract. In this talk, we will discuss some work in progress concerning giving a formal analysis of the cryptographic concept of a zero knowledge proof as an epistemic logic. We will introduce a family of multimodal, non-normal modal logics induced by adding to EK4 a "zero knowledge axiom" indicating the non-transferability of zero knowledge proofs between agents and show how to characterize the logics with neighborhood models with regular frames. We will then consider a hierarchy of non-normal extensions to EK4 characterized by their "contranormality" i.e. that they have no normal extensions. We will conclude by investigating how to provide explicit justification logic versions of these logics. (Joint work with Eke Gertler and Jitka Kadlecikova)

- - - - Wednesday, Apr 9, 2025 - - - -

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: Emilio Minichiello, CUNY CityTech.

Date and Time: Wednesday April 9, 2025, 7:00 - 8:30 PM. IN PERSON TALK.

Title: Structured Decomposition Categories.

Abstract: In this talk I’ll report on some new work, joint with Ben Bumpus, Zoltan Kocsis and Jade Master. The idea here is to come up with a categorical framework to talk about decompositions. In graph theory, there are all kinds of ways of decomposing graphs, the most important being tree decompositions. This is a way to decompose a graph into pieces in such a way that if you squint at it, it looks like a tree. By looking at the biggest piece and minimizing over all tree decompositions, one obtains treewidth, the most important graph invariant in algorithmics. In this paper, we abstract this notion, coming up with the definition of structured decomposition categories. To each such category, we can assign to each of its objects a width number. We prove that this number is monotone under monomorphisms, and come up with an appropriate definition of structured decomposition functor such that we get a relationship between widths. We construct several examples of structured decomposition categories, whose widths coincide with several important examples from the literature.

- - - - Thursday, Apr 10, 2025 - - - -

- - - - Friday, Apr 11, 2025 - - - -

*** CUNY Graduate Center Spring Recess 4/12-4/20 ***

Next Week in Logic at CUNY:

- - - - Monday, Apr 14, 2025 - - - -

*** CUNY Graduate Center Spring Recess 4/12-4/20 ***

- - - - Tuesday, Apr 15, 2025 - - - -

*** CUNY Graduate Center Spring Recess 4/12-4/20 ***

- - - - Wednesday, Apr 16, 2025 - - - -

*** CUNY Graduate Center Spring Recess 4/12-4/20 ***

- - - - Thursday, Apr 17, 2025 - - - -

*** CUNY Graduate Center Spring Recess 4/12-4/20 ***

- - - - Friday, Apr 18, 2025 - - - -

*** CUNY Graduate Center Spring Recess 4/12-4/20 ***

- - - - Other Logic News - - - -

Conference Announcement: Special Session to Honor Jim Schmerl on His 85th Birthday
VIrtual

Tuesday, April 22nd, 11am-5:30pm

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Session 1 (11:00 AM - 1:30 PM):
11:00 - 11:05 Welcome
11:05 - 11:35 Angus Macintyre
11:40 - 12:10 Ali Enayat
12:10 - 12:25 Coffee break
12:25 - 12:55 Ermek Nurkhaidarov
1:00 - 1:30 Stephen Simpson

Session 2 (3:00 - 5:30 PM)
3:00 - 3:30 David Marker
3:35 - 4:05 Manuel Lerman
4:05 - 4:20 Coffee break
4:20 - 4:50 Matt Kaufmann
4:55 - 5:30 There is still work to be done.

GlaD (Groups, Logic, and Dynamics) meeting

Saturday, April 12

Rutgers University, New Brunswick.

This is the third installment of the meeting in Groups, Logic and Dynamics. We will be meeting in New Brunswick at the beginning of the spring season.

Limited funding for junior and local participants are available. Please contact the organizers to apply and check availability.
https://sites.math.rutgers.edu/~fc327/GLaDS2025/index.html

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

Logic Seminar Wed 9 Apr 2025 17:00 hrs at NUS by Frank Stephan

NUS Logic Seminar

4/7/2025 4:04:34

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 9 April 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Frank Stephan Title: The Computational Complexity of Unfriendly Graph Partitions URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: For an unfriendly partition, one colours the nodes of a graph using k colours (mostly, k in {2,3}) such that for each two distinct colours a,b and each node of colour a, this node has more neighbours of colour b than of colour a. If one requires ``strictly more'' then the colouring is called ``strictly unfriendly'' and if one requires ``more or at least as many'' then the colouring is just called ``unfriendly''. The sets of the the nodes of each colour form then a partition of the graph. For two colours, one knows that every finite graph has an unfriendly partition while for countable graphs this is an open problem and for uncountable graphs, this is false, as shown by Shelah and Milner [1990]. Joint work with Belanger, Cipriani, Goh, Richter and Tang shows that for certain recursive graphs, constructing an unfriendly colouring with two colours cannot be solved by any hyperarithmetic oracle, though a more complicated colouring still exists. Thus one cannot expect to find an easy algorithm solving the task and this might be one of the reasons that the problem is still open. Haynes, Hedetniemi and Vasylieva [2015] showed that for two colours, even finite graphs might fail to have a strictly unfriendly colouring. Indeed, it is shown that constructing strictly unfriendly colourings for two or three colours on finite graphs requires, under the Exponential Time Hypothesis, exponential time. Furthermore, one can reduce the problem 3occur3SAT with n variables to the problem of finding an unfriendly colouring of a finite graph with n' nodes such that the lower bound c^n for 3occur3SAT translates into the lower bound (c^2/11)^n'. These constant c is not explicitly known, but under the assumption ETH it is strictly between 1 and 2. If one only considers graphs of bounded degree, also nontrivial bounds on the runtime can be obtained. Similar results are obtained for three colours. This is joint work with Sanjay Jain and Haoyun Tang. Furthermore, the three authors joint with Ong Weng Qi investigated the complexity of finding unfriendly colourings for two or three colours when for some nodes some colours are preassigned. This was known to be NP-hard, but the finegrained complexity was not studied before.

73rd Nankai Logic Colloquium

Nankai Logic Colloquium

4/7/2025 6:30:54

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Patrick Lutz from the University of California, Berkeley. This talk will take place this Friday, April 11th, from 9am to 10am (UTC+8, Beijing time).

Title: Measure hyperfiniteness and lossless expansion

Abstract: The structure of the class of countable Borel equivalence relations under Borel reducibility has been a major focus of descriptive set theory over the past few decades. However, many open questions remain, a number of which involve the class of hyperfinite equivalence relations (essentially the simplest nontrivial countable Borel equivalence relations). In order to better understand these questions, Conley and Miller introduced a weakening of Borel reducibility, known as measure reducibility. They then answered the analogues for measure reducibility of several open questions involving hyperfinite equivalence relations. However, they left open at least one such question. Namely, is there a minimal non-hyperfinite equivalence relation under the relation of measure reducibility? Such an object is called a "measure successor of $E_0$." In ongoing work, Jan Greb\'ik and I have isolated a combinatorial property of group actions on Polish spaces which implies that the associated orbit equivalence relation is a measure successor of $E_0$. We have also identified several examples of group actions which are plausible candidates for satisfying this condition. The combinatorial property we have identified is a strong form of graph expansion which we call "lossless expansion" after a similar property studied in computer science and combinatorics. I will explain the context for Conley and Miller's question and the combinatorial condition that Greb\'ik and I have isolated and then sketch the main ideas which relate this combinatorial condition to hyperfiniteness.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 73rd Nankai Logic Colloquium-- Patrick Lutz Time: 9:00am, Apr. 11, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=91835496156

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Wednesday seminar

Prague Set Theory Seminar

4/11/2025 10:44:15

Dear all, The seminar meets on Wednesday April 16th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Julia Ścisłowska -- When your arc-like space looks like an arc (and when not)? The talk will be based on the results from my master’s thesis, prepared under supervision of prof. Witold Marciszewski. During my talk I will introduce the notion of an ultrafilter order on any arc-like continuum $X$, which depends on a fixed sequence of chains, covering $X$ and on fixed nonprincipal ultrafilter on $\N$. It may be also defined using representation of $X$ as an inverse limit of a sequence of arcs and a fixed nonprincipal ultrafilter on $\N$. I will present some results concerning ultrafilter orders on arc-like continua. In particular, I will discuss what does it mean to look like an arc from the ultrafilter orders' point of view. I will give some examples of spaces that have properties such as an arc (for example, there are some arc-like spaces, which are not an arc, but have an ordertype of the arc when equipped with an ultrafilter order) and I will also give an example of a space which doesn't have properties such as an arc (it will be the Knaster continuum equipped with an order topology generated by a certain ultrafilter order). I will also show that an arc is the only arc-like continuum on which there exists a closed ultrafilter order. Best, David

No Nankai Logic Colloquium this week

Nankai Logic Colloquium

4/14/2025 8:56:27

Hello everyone,

Due to the 2025 CACML (Chinese Annual Conference on Mathematical Logic), there is no Nankai Logic Colloquium talk this week. We will resume our colloquium next week on April 22(Tuesday).

Thank you for your understanding!

Best regards,

Wei

Logic Seminar 16 April 2025 17:00 hrs at NUS by Isabella Scott, Wellington

NUS Logic Seminar

4/14/2025 4:02:51

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 April 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Isabella Scott Title: The structure of the Ziegler degrees and connections to model theory Abstract: Ziegler-reducibility (written ≤*) was introduced by Martin Ziegler in his investigations into finitely generated subgroups of existentially closed (e.c.) groups. It is a refinement of both enumeration- and Turing-reducibility and agrees with Q-reducibility on the c.e. sets. Remarkably, Ziegler showed that it can be characterised purely algebraically: for finitely generated G and H, W(H) ≤* W(G) if and only if H embeds in every e.c. group containing G. In this talk, I shall discuss the connections between computability theory and existentially closed groups, and recent work on the structure of the Ziegler degrees. In particular, we show that there is a minimal Ziegler degree, and, generalising this construction, that the 3-quantifier theory of the Ziegler degrees is undecidable. This is joint work with Steffen Lempp and Josiah Jacobsen-Grocott. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar

4/17/2025 8:24:42

Dear all, The seminar meets on Wednesday April 23rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Luis David Reyes Saenz -- Q-points, Q-measures and other special measures I will talk about some recent developments regarding Q-points and Q-measures and their relation to problems in other areas of mathematics. In particular, I will present two characterizations of Q-points: one similar to the classical Mathias' theorem for selective ultrafilters, the other one uses the language of L-orthogonal sequences and L-orthogonal elements in Banach Spaces. I will also talk about some generalizations of Q-points in the realm of finitely-additive measures over P(omega), and some new results about them. The results are consequence of joint work with Antonio Aviles, Michael Hrusak, Gonzalo Martinez-Cervantes, and Alejandro Poveda. Best, David

This Week in Logic at CUNY

4/20/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Apr 21, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 21, 2-4pm (NY time)
Room: Graduate Center Room 7395

Speaker: Jacob McNulty (Yale)
Title: A hole within being: Consciousness as nothingness in the early Sartre

Abstract: Among Sartre’s best-known theses in Being and Nothingness is his claim that the world of experience contains what he calls “négatités,” little pools or pockets of nothingness. The most famous example of a négatité is Pierre, the friend who is absent from the café. Sartre’s conviction that there are négatités all around us has another side, often obscured from view: I mean his (apparent) conviction that we ourselves are a kind of non-being or nothingness. In this paper I try to shed some light on this Sartrean thesis by connecting it to perennial problem in metaphysics concerning the status of holes, shadows or absences — in short, non-beings. However I see more than mere analogy here. Sartre’s view, as I understand it, is that we literally are a type of hole. We are holes in the sense that we are the kinds of nonbeings that require beings as our hosts. More accurately, it is being and not beings that host the holes that we are. Ordinary holes have some particular material thing as their hosts: cheese or fabric. Yet our “host” is not any particular being (cheese or fabric) but being itself: the in-itself [en soi].

Rutgers Logic Seminar
Monday April 21, 3:30pm, Rutgers University, Hill Center, Hill 705

Omer Ben-Neria, Hebrew University
Careful Iterations

- - - - Tuesday, Apr 22, 2025 - - - -

Special Session to Honor Jim Schmerl on His 85th Birthday
Virtual

Tuesday, April 22nd, 11am-5:30pm

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Session 1 (11:00 AM - 1:30 PM):
11:00 - 11:05 Welcome
11:05 - 11:35 Angus Macintyre
11:40 - 12:10 Ali Enayat
12:10 - 12:25 Coffee break
12:25 - 12:55 Ermek Nurkhaidarov
1:00 - 1:30 Stephen Simpson

Session 2 (3:00 - 5:30 PM)
3:00 - 3:30 David Marker
3:35 - 4:05 Manuel Lerman
4:05 - 4:20 Coffee break
4:20 - 4:50 Matt Kaufmann
4:55 - 5:30 There is still work to be done.

Computational Logic Seminar

Spring 2025 (in-person + zoom - for zoom link, please contact Sergei Artemov sartemov@gmail.com)

Tuesday, April 22, Time 2:00 - 4:00 PM, Graduate Center, rm. 3308
Speaker: Sreehari Kalloormana, Graduate Center CUNY
Title: Defeasible Logics and Argumentation.

Abstract. Defeasible logics are those in which conclusions can be defeated or blocked when additional information is revealed. The study of defeasible logics took off in the 1980s following seminal works by Pollock, Nute, and others. It has since found important applications in AI, computational law, and philosophy. We examine Pollock-style defeasible logics, various semantics developed for them, and their use in the formal study of argumentation. Time-permitting we will also sketch recent work on defeasible logics by introducing ordering over reasons in justification logic.

- - - - Wednesday, Apr 23, 2025 - - - -

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: Andrei Rodin, University of Lorraine.
Date and Time: Wednesday April 23, 2025, 7:00 - 8:30 PM. IN PERSON TALK!!!
Title: The concept of mathematical structure according to Voevodsky.

Abstract: In our email exchange dating back to 2016 Vladimir Voevodsky suggested an original conception of mathematical structure, which was motivated, on the one hand, by his work in the Homotopy Type theory and, on the other hand, by his reading of Proclus’ commentary on Euclid’s definition of plane angle (Def. 1.8. of the Elements). In my talk I present Vladimir’s conception of mathematical structure, compare it with standard conceptions, and discuss some questions asked by Vladimir during the same exchange. The talk is based on this paper: arXiv:2409.02935

- - - - Thursday, Apr 24, 2025 - - - -

- - - - Friday, Apr 25, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, April 25, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Catalina Torres Pachon, University of Barcelona
A Topological Approach to Characterising Hyperstationary Sets on

Given a topological space , the derived set operator maps a set to its set of limit points with respect to . Fixing an initial topology on , we can define a sequence of derived topologies , where for . This is achieved by declaring to be open in and taking unions at limit stages.

In Derived Topologies on Ordinals and Stationary Reflection, Bagaria characterised the non-isolated points in the -th derived topology on ordinals as those satisfying a strong iterated form of stationary reflection, termed -simultaneous reflection.

Generalisations of combinatorial properties of ordinals to , where is an uncountable regular cardinal and , have been widely studied. In this context, we extend the notion of higher stationarity and construct a sequence of topologies on , characterising the simultaneous reflection of high-stationary subsets of in terms of elements in the base of a derived topology on .

Logic Workshop

CUNY Graduate Center
Friday, April 25, 2:00pm-3:30pm, Room 5417

Johanna Franklin, Hofstra University
Failure modes for highness notions

We say that a Turing degree is high in some context if it can always compute a correct answer given an input for which this is possible. When no correct answer is possible, however, what might such a degree do? We explore the possibilities in the context of computable structure theory. This is joint work with Wesley Calvert and Dan Turetsky.

Next Week in Logic at CUNY:

- - - - Monday, Apr 28, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 28, 2-4pm (NY time)
Room: Graduate Center Room 7395

Graham Priest, CUNY
The Moebius World (Abstract)

As many philosophers have noted, we have two takes on the world: the view from nowhere and the view from here. In the latter the cognitive agent occupies a privileged position; in the former they do not. But the two views are contradictory. Reality has two sides, as it were, like a ring made of paper, each side contradicting the other. In fact the two views are more intimately related to each other that this, since each presupposes the other. Reality is, then, more like what happens when you put a twist in the ring, producing a Moebius strip. There is just one side which is self-contradictory. The talk explores these matters.

Rutgers Logic Seminar
Monday April 28, 3:30pm, Rutgers University, Hill Center, Hill 705

James Cummings, CMU

- - - - Tuesday, Apr 29, 2025 - - - -

- - - - Wednesday, Apr 30, 2025 - - - -

- - - - Thursday, May 1, 2025 - - - -

- - - - Friday, May 2, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, May 2, 12:30pm NY time, Room: 5417

Nigel Pynn-Coates, University of Vienna

Logic Workshop

CUNY Graduate Center
Friday, May 2, 2:00pm-3:30pm, Room 5417

Nigel Pynn-Coates, 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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74th Nankai Logic Colloquium

Nankai Logic Colloquium

4/21/2025 3:21:22

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon at an unusual time (April 22, Tuesday). Our speaker this week will be Theodore Slaman from the University of California, Berkeley. This talk will take place this Tuesday, April 22rd, from 4pm to 5pm (UTC+8, Beijing time).

Title: Hausdorff Dimension, Capacitability and Mathematical Logic

Abstract: We pose the question "To what extent can the size/dimension of a set A ⊆ Rn be duplicated by a closed C ⊆ A?" For analytic sets, classical theorems establish a pattern of size-filling closed subsets. Consistently with ZFC, this pattern can fail for co-analytic sets for Hausdorff dimension. Further, for the more finely-calibrated criterion of gauge dimension, the reverse pattern appears: there are low-level Borel subsets of the real line with strictly greater gauge dimension than can be realized by any of their closed subsets.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 74th Nankai Logic Colloquium-- Theodore Slaman Time: 16:00pm, Apr. 22, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=99495471895

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

This Week in Logic at CUNY

4/27/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Apr 28, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 28, 2-4pm (NY time)
Room: Graduate Center Room 7395

Graham Priest, CUNY
The Moebius World (Abstract)

As many philosophers have noted, we have two takes on the world: the view from nowhere and the view from here. In the latter the cognitive agent occupies a privileged position; in the former they do not. But the two views are contradictory. Reality has two sides, as it were, like a ring made of paper, each side contradicting the other. In fact the two views are more intimately related to each other that this, since each presupposes the other. Reality is, then, more like what happens when you put a twist in the ring, producing a Moebius strip. There is just one side which is self-contradictory. The talk explores these matters.

Rutgers Logic Seminar
Monday April 28, 3:30pm, Rutgers University, Hill Center, Hill 705

James Cummings, CMU

The tree property at predecessors of singular cardinals

- - - - Tuesday, Apr 29, 2025 - - - -

Computational Logic Seminar
Spring 2025 (in-person + zoom - for zoom link, please contact Sergei Artemov sartemov@gmail.com)
Tuesday, April 29, Time 2:00 - 4:00 PM, Graduate Center, rm. 3308
Speaker: Roman Kuznets, Institute of Computer Science of the Czech Academy of Sciences
Title: Impure Simplicial Complexes: From Global to Local and Back Again

Abstract. Formally, (pure) simplicial complexes provide a semantics that is alternative, yet categorically equivalent to Kripke models for multiagent epistemic logic S5. There is supposed to be no difference whether one looks at things objectively (Kripke semantics) or subjectively (simplicial semantics). Things get murkier when some of the subjects may disappear, as is the case for distributed systems with crashes. This presents a number of choices for the so-called impure simplicial complexes, for propositional connectives (e.g., boolean two-valued, or Weak Kleene three-valued, or Strong Kleene three-valued logic), for the knowledge modalities (e.g., is knowledge of crashed agents factive?), and even for the propositional variables (local vs. global variables). In the talk, we will discuss these choices, point out the unreasonable ones, and try to establish a minimally expressive language faithful to the impure simplicial semantics, based on the logical property desiderata, such as the Hennessy–Milner property.

Based on joint work with (various subsets of) Marta Bílková, Hans van Ditmarsch, and Rojo Randrianomentsoa.

- - - - Wednesday, Apr 30, 2025 - - - -

- - - - Thursday, May 1, 2025 - - - -

- - - - Friday, May 2, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, May 2, 12:30pm NY time, Room: 5417

Nigel Pynn-Coates, University of Vienna

D-minimality and more for the asymptotic couple of the field of logarithmic transseries

Associated to certain valued differential fields like transseries and Hardy fields are so-called asymptotic couples, which were introduced by M. Rosenlicht. These are ordered abelian groups equipped with a map induced by the derivation of the valued differential field. I will describe ongoing work with A. Gehret and E. Kaplan on the asymptotic couple of the field of logarithmic transseries, in which we show various notions of smallness coincide. For example, the structure is d-minimal in the sense that every unary definable set with empty interior is a finite union of discrete sets. This enables us to classify all dimension functions on the structure.

Logic Workshop

CUNY Graduate Center
Friday, May 2, 2:00pm-3:30pm, Room 5417

Nigel Pynn-Coates, University of Vienna
Transserial tame pairs

Interest in transseries and Hardy fields comes from several fields, including asymptotic analysis, dynamical systems, and model theory of the real numbers. The first-order theory of (logarithmic-exponential) transseries and maximal Hardy fields is completely axiomatized by the theory of closed H-fields, which is model complete, as Aschenbrenner, Van den Dries, and Van der Hoeven have shown in a long series of works. I will describe my extension of this model completeness to tame pairs of closed H-fields, in order to better understand large closed H-fields, such as maximal Hardy fields, hyperseries, or surreal numbers. Time permitting, I may mention ongoing work on differential-algebraic dimension in transserial tame pairs.

Next Week in Logic at CUNY:

- - - - Monday, May 5, 2025 - - - -

Rutgers Logic Seminar
Monday May 5, 3:30pm, Rutgers University, Hill Center, Hill 705

Alejandro Poveda, Harvard
Recent progress on the study of HOD

Logic and Metaphysics Workshop
Date: Monday, May 5, 2-4pm (NY time)
Room: Graduate Center Room 7395
Luca Incurvati (ILLC).
Title: On class hierarchies

Abstract: In her seminal article ‘Proper Classes’, Penelope Maddy introduced a theory of classes validating the naïve comprehension rules. The theory is based on a step-by-step construction of the extension and anti-extension of the membership predicate, which mirrors Kripke’s construction of the extension and anti-extension of the truth predicate. Maddy’s theory has been criticized by Øystein Linnebo for its ‘rampant indeterminacy’ and for making identity among classes too fine-grained. In this paper, I present a theory of classes that builds on Maddy’s theory but avoids its rampant indeterminacy and allows for identity among classes to be suitably coarse-grained. For all the systems I discuss, I provide model theories and proof theories (formulated in bilateral natural deduction systems), along with suitable soundness and completeness results.

- - - - Tuesday, May 6, 2025 - - - -

- - - - Wednesday, May 7, 2025 - - - -

- - - - Thursday, May 8, 2025 - - - -

- - - - Friday, May 9, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, May 9, 12:30pm NY time, Room: 5417

Michele Bailetti Wesleyan University

Logic Workshop

CUNY Graduate Center
Friday, May 9, 2:00pm-3:30pm, Room 5417

Charles Steinhorn Vassar College

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

No Nankai Logic Colloquium this week

Nankai Logic Colloquium

4/28/2025 1:43:10

Hello everyone,

Due to holidays in China, there is no Nankai Logic Colloquium talk this week. We will resume our regular schedule next week on May 9.

Thank you for your understanding!

Best regards,

Wei

Wednesday seminar

Prague Set Theory Seminar

4/28/2025 4:38:56

Dear all, The seminar meets on Wednesday April 30th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet fixed. Best, David

This Week in Logic at CUNY

5/4/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, May 5, 2025 - - - -

Rutgers Logic Seminar
Monday May 5, 3:30pm, Rutgers University, Hill Center, Hill 705

Alejandro Poveda, Harvard
Recent progress on the study of HOD

Logic and Metaphysics Workshop
Date: Monday, May 5, 2-4pm (NY time)
Room: Graduate Center Room 7395
Luca Incurvati (ILLC).
Title: On class hierarchies

Abstract: In her seminal article ‘Proper Classes’, Penelope Maddy introduced a theory of classes validating the naïve comprehension rules. The theory is based on a step-by-step construction of the extension and anti-extension of the membership predicate, which mirrors Kripke’s construction of the extension and anti-extension of the truth predicate. Maddy’s theory has been criticized by Øystein Linnebo for its ‘rampant indeterminacy’ and for making identity among classes too fine-grained. In this paper, I present a theory of classes that builds on Maddy’s theory but avoids its rampant indeterminacy and allows for identity among classes to be suitably coarse-grained. For all the systems I discuss, I provide model theories and proof theories (formulated in bilateral natural deduction systems), along with suitable soundness and completeness results.

- - - - Tuesday, May 6, 2025 - - - -

Computational Logic Seminar
Spring 2025 (in-person + zoom - for zoom link, please contact Sergei Artemov sartemov@gmail.com)
Tuesday, May 6, Time 2:00 - 4:00 PM, CUNY Graduate Center, rm. 3308
Speaker: Giorgi Japaridze, Villanova University
Title: Do not throw the baby (Peano axioms) out

Abstract: I shall briefly survey arithmetical theories based on the game-semantically conceived Computability Logic. Such theories, dubbed “clarithmetics”, allow us to naturally and systematically capture various computational complexity classes, and do this in a stronger sense than weak arithmetics (e.g. bounded arithmetics) do. Specifically, due to being extensions rather than restrictions of PA, clarithmetics achieve not only extensional but also intensional completeness with respect to their target complexity classes. The underlying concept of computability in clarithmetics is also more general than the traditional one, in that it is about interactive problems rather than merely about functions, with the latter seen as just degenerate special cases of interactive problems.

In this world of interactive computability, some unusual phenomena occur. E.g., space complexity is not necessarily upper-bounded by time complexity; not all computable problems have computable time complexities; interactive P can be provably separated from interactive PSPACE; and more. An online survey of the subject can be found at http://www.csc.villanova.edu/~japaridz/CL/

- - - - Wednesday, May 7, 2025 - - - -

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: Sergei Artemov, Graduate Center CUNY.
Date and Time: Wednesday May 7, 2025, 7:00 - 8:30 PM. IN PERSON TALK!!!
Title: Consistency of PA is a serial property, and it is provable in PA.

Abstract: We show that PA consistency is mathematically equivalent to the serial property, which we call the consistency scheme ConS(PA):
"n is not a proof of 0=1", for n=0,1,2,... .

The proof of this equivalence is formalizable in PA. Since the standard consistency formula Con(PA)
"for all x, x is not a code of a proof of 0=1"

is strictly stronger than the scheme ConS(PA) in PA, Goedel's Second Incompleteness theorem, stating that PA |-\- Con(PA) does not yield the unprovability of PA consistency. Hence, the widespread belief that a consistent theory cannot establish its consistency has never been justified.

Moreover, we show that this belief is false. The question of proving PA consistency in PA reduces to proving the scheme ConS(PA) in PA. We build on Hilbert's ideas and prove ConS(PA) in PA.

This talk is a "dress rehearsal" for the speaker's plenary talk at the ASL meeting on May 13, 2025.

Reference:
S.Artemov "Serial Properties, Selector Proofs, and the Provability of Consistency," Journal of Logic and Computation, Volume 35, Issue 3, April 2025. https://doi.org/10.1093/logcom/exae034, Published: 26 July 2024.

- - - - Thursday, May 8, 2025 - - - -

- - - - Friday, May 9, 2025 - - - -

Model Theory Seminar

CUNY Graduate Center
Friday, May 9, 12:30pm NY time, Room: 5417

Michele Bailetti, Wesleyan University
Notions of maximality in first-order theories

In the classification of complete first-order theories, many dividing lines have been defined in order to understand the complexity and the behavior of some classes of theories. In this talk, using the concept of patterns of consistency and inconsistency, we describe a general framework to study combinatorially defined dividing lines and we introduce a notion of maximal complexity by requesting the presence of all the exhibitable patterns of definable sets. Weakening this notion, we define new properties (Positive Maximality and the hierarchy) and prove some results about them.

Logic Workshop

CUNY Graduate Center
Friday, May 9, 2:00pm-3:30pm, Room 5417

Charles Steinhorn Vassar College

Next Week in Logic at CUNY:

- - - - Monday, May 12, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 12, 2-4pm (NY time)
Room: Graduate Center Room 7395
Mircea Dumitru (Bucharest)
Title: Does a Tarskian theory of truth offer a theory of meaning? A Sellarsian-type evaluation and critique of Donald Davidson’s truth-conditional semantics

Abstract: The paper examines how problems with Davidson’s truth-conditional semantics can be fixed through Sellars’ brand of inferentialism. I begin by presenting Davidson’s truth-conditional semantics for a natural language, viz. the program according to which the meaning of a language is to be given by a Tarskian truth-theory for that language. Against this background, I build a scenario in which a competent logician can give a truth-theory for sentences of a language that he/she cannot speak/read/understand without thereby giving/knowing/understanding the meaning of the sentences that he/she cannot comprehend. The logician knows that the sentences in the unknown (for him/her) language are true but, nevertheless, he/she does not know what they mean. In order to fix this drawback of the Davidsonian truth-conditional based theory of meaning, I present the main elements of Sellars’ subtle views on meaning and truth, pointing at how the latter can circumvent the problems with the extensional Tarskian truth-conditional approach put forward by Davidson.

- - - - Tuesday, May 13, 2025 - - - -

- - - - Wednesday, May 14, 2025 - - - -

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: Raymond Puzio.
Date and Time: Wednesday May 14, 2025, 7:00 - 8:30 PM. IN PERSON TALK
Title: Gentle Introduction to Synthetic Differential Geometry --- Part two.

Abstract: This is part II of "Gentle introduction to synthetic differential geometry". This talk will be self contained and not assume familiarity with part one. Moreover, the approach and topics covered this time will be sufficiently different that it will be of interest to people who attended part one.

In part one, we introduce the topic in a "bottom-up" manner starting with the simplest instance and building up in complexity. In part two, we will introduce the subject in a "top-down" manner where we begin by postulating a category with certain properties and proceeding from these postulates.

After introducing the topic, we will turn to Lie groups as an illustrative application. Intuitively, to make a presentation of a Lie group by generators and relations, we would want to pick infinitessimal transformations for generators. This is not possible in classical differential geometry so one must instead employ various work-arounds. However, in synthetic differential geometry, infinitessimal generators are well defined and we can build up Lie theory in a way which accords with naive intuition. In this talk, we shall go through the first few steps of this development. Then we shall note how the synthetic approach is not only more intuitive but more powerful because it allows us to extend the notion of Lie group beyond finite-dimensional manifolds to which the classical approach is limited. We will also say a few words about how the some of these infinite-dimensional generalizations are of use in in practical applications.

- - - - Thursday, May 15, 2025 - - - -

- - - - Friday, May 16, 2025 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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75th Nankai Logic Colloquium

Nankai Logic Colloquium

5/5/2025 10:59:49

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Bo Peng from McGill University. This talk will take place this Friday, May 9th, from 9am to 10am (UTC+8, Beijing time).

Title: Anti-classification results for minimal and smooth dynamics

Abstract: Classification problems play an important role in dynamical systems. In 1907, Poincaré proved that any minimal homeomorphism on the circle can be classified by its rotation number. A natural question is: Can we generalize this theorem to the 2-Torus? In 1967, Smale suggested a program to classify diffeomorphisms of a manifold by topological conjugacy. Is this program possible? In this talk, I will discuss the following results:

1. The conjugacy relation of rotations on the 2-Torus is not smooth which answers a question of Foreman.

2. Let M be a manifold with dim(M ) ≥ 2, the topological conjugacy of diffeomorphisms on M is not classifiable by countable structures. This answers a question of Foreman and Gorodetski.

3. The conjugacy relation of minimal homeomorphisms on the 2-Torus is not classifiable by countable structures.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 75th Nankai Logic Colloquium-- Bo Peng Time: 9:00am, May. 9, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=94699475999

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Wednesday seminar

Prague Set Theory Seminar

5/5/2025 11:39:32

Dear all, The seminar meets on Wednesday May 7th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie Hanson -- Automorphisms of reduced products and nontrivial coherent families In a recent paper, de Bondt, Farah, and Vignati studied isomorphisms between reduced products of countable models. They showed that, for models of certain theories, OCA+MA implies that all such isomorphisms are "trivial". Their proof involved two applications of OCA; one to show that all such isomorphisms "preserve coordinates", and another to show that all coordinate-preserving isomorphisms are trivial. This raises natural questions about the extent to which OCA is necessary for both of these steps. We will discuss some easy, preliminary observations motivated by these questions. In particular, we will discuss the use of nontrivial coherent families of functions to induce nontrivial coordinate-preserving isomorphisms. We will also show that CH implies the existence of nontrivial coordinate-preserving automorphisms of \prod_omega Z/fin. This is joint and ongoing work with Alessandro Vignati. Best, David

Wednesday seminar

Prague Set Theory Seminar

5/7/2025 8:26:08

Dear all, The seminar meets on Wednesday May 14th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jindřich Zapletal -- Cohomology of amalgamation diagrams I define amalgamation diagram problems for models of set theory. I show how answers to such problems can lead to independence results in set theory. For some amalgamation diagram problems, their resolution amounts to calculating cohomology groups of certain natural cochain complexes. Best, David

KGRC Set Theory talk May 15

Kurt Godel Research Center

5/9/2025 6:56:12

KGRC/Institute of Mathematics invites you to the following talk: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, May 15, 11:30am--1:00pm, hybrid mode "Infinite Cardinal Exponentiation II" W. Chan (TU Wien) In this 3 talk series (part 1: https://kgrc.univie.ac.at/research/seminars-at-the-kgrc/set-theory/full-news-display/news/infinite-cardinal-exponentiation-i/; this is part2) we will discuss about the cardinality of familiar sets in choiceless universes possessing strong regularity properties. In particular, we will address the cardinality comparison between infinite cardinal exponentiation. As time permits, a deeper analysis of the cardinality for exponent omega which is the smallest nonwellorderable cardinal exponentiation will be considered. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recording available so far from the Set Theory Seminar: May 8: W. Chan (TU Wien). "Infinite Cardinal Exponentiation I" https://ucloud.univie.ac.at/index.php/s/cR7RfYpg3PBrFfj Video recording available so far from the Logic Colloquium: May 8: H. Ben-Yami (Central European U, Vienna): "The Quantified Argument Calculus: Introduction and Research Directions" https://ucloud.univie.ac.at/index.php/s/LJDxxxr5SZmmZd7 -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

5/11/2025 22:42:00

This Week in Logic at CUNY:

- - - - Monday, May 12, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 12, 2-4pm (NY time)
Room: Graduate Center Room 7395
Mircea Dumitru (Bucharest)
Title: Does a Tarskian theory of truth offer a theory of meaning? A Sellarsian-type evaluation and critique of Donald Davidson’s truth-conditional semantics

Abstract: The paper examines how problems with Davidson’s truth-conditional semantics can be fixed through Sellars’ brand of inferentialism. I begin by presenting Davidson’s truth-conditional semantics for a natural language, viz. the program according to which the meaning of a language is to be given by a Tarskian truth-theory for that language. Against this background, I build a scenario in which a competent logician can give a truth-theory for sentences of a language that he/she cannot speak/read/understand without thereby giving/knowing/understanding the meaning of the sentences that he/she cannot comprehend. The logician knows that the sentences in the unknown (for him/her) language are true but, nevertheless, he/she does not know what they mean. In order to fix this drawback of the Davidsonian truth-conditional based theory of meaning, I present the main elements of Sellars’ subtle views on meaning and truth, pointing at how the latter can circumvent the problems with the extensional Tarskian truth-conditional approach put forward by Davidson.

- - - - Tuesday, May 13, 2025 - - - -

- - - - Wednesday, May 14, 2025 - - - -

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: Raymond Puzio.
Date and Time: Wednesday May 14, 2025, 7:00 - 8:30 PM. IN PERSON TALK

CUNY Graduate Center Room 6496
Title: Gentle Introduction to Synthetic Differential Geometry --- Part two.

Abstract: This is part II of "Gentle introduction to synthetic differential geometry". This talk will be self contained and not assume familiarity with part one. Moreover, the approach and topics covered this time will be sufficiently different that it will be of interest to people who attended part one.

In part one, we introduce the topic in a "bottom-up" manner starting with the simplest instance and building up in complexity. In part two, we will introduce the subject in a "top-down" manner where we begin by postulating a category with certain properties and proceeding from these postulates.

After introducing the topic, we will turn to Lie groups as an illustrative application. Intuitively, to make a presentation of a Lie group by generators and relations, we would want to pick infinitessimal transformations for generators. This is not possible in classical differential geometry so one must instead employ various work-arounds. However, in synthetic differential geometry, infinitessimal generators are well defined and we can build up Lie theory in a way which accords with naive intuition. In this talk, we shall go through the first few steps of this development. Then we shall note how the synthetic approach is not only more intuitive but more powerful because it allows us to extend the notion of Lie group beyond finite-dimensional manifolds to which the classical approach is limited. We will also say a few words about how the some of these infinite-dimensional generalizations are of use in in practical applications.

- - - - Thursday, May 15, 2025 - - - -

- - - - Friday, May 16, 2025 - - - -

Next Week in Logic at CUNY:

- - - - Monday, May 19, 2025 - - - -

- - - - Tuesday, May 20, 2025 - - - -

- - - - Wednesday, May 21, 2025 - - - -

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: Raymond Puzio.
Date and Time: Wednesday May 21, 2025, 7:00 - 8:30 PM. IN PERSON TALK

CUNY Graduate Center Room 6496
Title: Gentle Introduction to Synthetic Differential Geometry --- Part two.

- - - - Thursday, May 22, 2025 - - - -

- - - - Friday, May 23, 2025 - - - -

- - - - Other Logic News - - - -

The Saul Kripke Center

Summer Logic Double Feature

June 11, 2025, 2-4pm, CUNY Graduate Center (Room 9207)

Title (1): A Theory of Definite Descriptions for Modal Logic
Time (1): 2:00 to 3:00 pm
Speaker (1): Nils Kürbis (Bochum)

Abstract (1): I’ll present a theory of definite descriptions in positive free logic, where definite descriptions ‘the F’ are formalised as in the context of complete sentences ‘The F is G’ by a binary quantifier as Ix(F, G). Formalised in natural deduction or sequent calculus, the theory satisfies certain proof-theoretic requirements demanded by proof theoretic semantics. Thus the meaning of I can be taken to be defined by its rules of inference. Positive free logic has been fruitfully applied in quantified modal logic. So I’ll consider what happens when modal operators are added. It turns out that the semantic clauses for Ix(F, G) are exactly those of Fitting and Mendelsohn (First Order Modal Logic, 2nd edition, Springer 2023), except that they formalise ‘The F is G’ by the iota operator for ‘the’ and the lambda for predicate abstraction to mark scope. I’ll end the talk with a brief comparison between the two systems.

Title (2): Solving a New Paradox of Deontic Logic (and a dozen other paradoxes) with RNmatrices for MC-based Modal Logics
Time (2): 3:00 to 4:00 pm
Speaker (2): Heinrich Wansing (Bochum) [joint work with Daniel Skurt (Bochum)]

Abstract (2): In this paper, we present RNmatrices (restricted non-deterministc matrices) for normal and non-normal modal expansions of the material connexive logic MC. We introduce and solve a paradox of deontic logic that to the best of our knowledge has not yet been been discussed in the literature and that justifies the use of a connexive, and actually hyperconnexive, non-modal base logic.

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

76th Nankai Logic Colloquium

Nankai Logic Colloquium

5/12/2025 2:59:56

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon. Our speaker this week will be Gabor Kun from the Alfred Renyi Institute of Mathematics and the Eotvos Lorand University. This talk will take place this Friday, May 16th, from 4pm to 5pm (UTC+8, Beijing time).

Title: On the measurable Hall condition

Abstract: Measurable perfect matchings have been intensively studied in the last decade. Most of the theorems use either the expansion of the corresponding measurable graph (Lyons-Nazarov theorem, Banach-Ruziewicz problem) or its hyperfiniteness (measurable and Borel solution to Tarski’s circle squaring problem). However, not many examples are known when there is no measurable perfect matching though the measurable Hall condition holds. Most examples admit two-ended components (i.e., of linear growth): in the hyperfinite case we characterized with Bowen and Sabok graphings without measurable perfect matchings via such obstructions. I explain this characterization and give applications from the measurable circle squaring to the amenable Lyons-Nazarov theorem.

In the second half of the talk I construct for every d ≥ 3 a d-regular acyclic measurably bipartite graphing that admits no measurable perfect matching. This answers a question of Kechris and Marks. A variant of this construction gives a free pmp action of the free product (Z/2Z)^∗d that admits no measurable non-trivial circulation. A denser version disproves a conjecture of Peled and Gurel-Gurevich on more dense measurable graphs (called permutons or Markov spaces). I give a probability measure on [0, 1]^2 whose marginals are equal to the Lebesgue measure on [0, 1], all of its sections are atomless but its support does not contain the graph of a measurable perfect matching.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 76th Nankai Logic Colloquium-- Gabor Kun Time: 16:00pm, May. 16, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=99065626126

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

KGRC Set Theory talk May 22

Kurt Godel Research Center

5/16/2025 6:50:01

KGRC/Institute of Mathematics invites you to the following talk: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, May 22, 11:30am--1:00pm, hybrid mode "Infinite Cardinal Exponentiation III" W. Chan (TU Wien) In this 3 talk series (part 1: https://kgrc.univie.ac.at/research/seminars-at-the-kgrc/set-theory/full-news-display/news/infinite-cardinal-exponentiation-i/; part2: https://kgrc.univie.ac.at/research/seminars-at-the-kgrc/set-theory/full-news-display/news/infinite-cardinal-exponentiation-ii/; this is part 3) we will discuss about the cardinality of familiar sets in choiceless universes possessing strong regularity properties. In particular, we will address the cardinality comparison between infinite cardinal exponentiation. As time permits, a deeper analysis of the cardinality for exponent omega which is the smallest nonwellorderable cardinal exponentiation will be considered. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, May 22, 3:00pm--3:50pm, hybrid mode "Semigroups Of Generalised Symmetries" Y. Peresse (U of Hertfordshire, UK) The symmetries of a geometric shape $X$ are the distance preserving functions $f:X \rightarrow X$. Of course, the concept of symmetry extends well beyond Geometry and into virtually every area of Mathematics. For example, if $X$ is a model-theoretic structure or a topological space, then its symmetries are the automorphisms and homeomorphisms of $X$, respectively. In each case, the symmetries of $X$ form a subgroup of the symmetric group $\Sym(X)$ of all permutations of $X$. There are two widely-studied and natural generalisations of the group $\Sym(X)$ to the world of semigroups. The \emph{Full Transformation Monoid} $X^X$ consists of all functions $f:X\rightarrow X$ and the \emph{Symmetric Inverse Monoid} consists of all bijections between subsets of $X$. These two semigroups correspond to two generalisations of the concept of symmetry as described above. For example, the group of automorphisms of a structure $X$ is a subgroup of the semigroup of homomorphisms $f:X\rightarrow X$ (which is a subsemigroup of $X^X$) and of the inverse semigroup of all isomorphisms between substructures of $X$ (which is an inverse subsemigroup of $I_X$). In this talk, we will consider Sym$(X)$, $X^X$, and $I_X$ on an infinite set $X$. I will present a variety of results which highlight the connections between Semigroups on the one hand and Set Theory, Model Theory, and Topology on the other. No previous knowledge of Semigroup Theory will be assumed. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. Video recording available so far from the Set Theory Seminar: May 15: W. Chan (TU Wien). "Infinite Cardinal Exponentiation II" https://ucloud.univie.ac.at/index.php/s/f8Q2jjYjZjFGr82 Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

Wednesday seminar

Prague Set Theory Seminar

5/18/2025 15:59:12

Dear all, The seminar meets on Wednesday May 21st at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There will be a couple of other things which might be of interest: Sean Cox will speak on Monday May 19th at the Algebra seminar, see here https://www.mff.cuni.cz/cs/math/ka/akce/seminare/algebraicky-seminar The Fifth European Set Theory Colloquium (online) will take place on Thursday May 22nd on Thursday, 22 May at 17:00 CETS, details here: https://ests.wordpress.com/panel-discussions/ Program (Wednesday): Adam Morawski -- The Rudin-Blass Ordering of Measures Finitely additive measures on omega can be viewed as a generalisation of ultrafilters. The talk will focus on combinatorics of measures based on methods used for ultrafilters -- in particular surrounding the Rudin-Blass and Rudin-Keisler orderings. It is well known that Q-points are exactly those ultrafilters that are Rudin-Blass minimal. It turns out that this is not exactly the case for measures. I will introduce the notion of Q-measures together with basic properties and provide a construction of a Rudin-Blass minimal measure which is not Q (and is far from it). Results mentioned in the talk are fruits of joint work with P. Borodulin-Nadzieja, A. Martinez-Celis and J. Świerczyńska. Best, David

This Week in Logic at CUNY

5/18/2025 22:43:00

Hi everyone,

This will be our last regular mailing until the start of the Fall semester. Have a good summer!

Best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, May 19, 2025 - - - -

- - - - Tuesday, May 20, 2025 - - - -

- - - - Wednesday, May 21, 2025 - - - -

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: Raymond Puzio.
Date and Time: Wednesday May 21, 2025, 7:00 - 8:30 PM. IN PERSON TALK

CUNY Graduate Center Room 6496
Title: Gentle Introduction to Synthetic Differential Geometry --- Part two.

- - - - Thursday, May 22, 2025 - - - -

- - - - Friday, May 23, 2025 - - - -

Next Week in Logic at CUNY:

- - - - Monday, May 26, 2025 - - - -

- - - - Tuesday, May 27, 2025 - - - -

- - - - Wednesday, May 28, 2025 - - - -

- - - - Thursday, May 29, 2025 - - - -

- - - - Friday, May 30, 2025 - - - -

- - - - Other Logic News - - - -

The Saul Kripke Center

Summer Logic Double Feature

June 11, 2025, 2-4pm, CUNY Graduate Center (Room 9207)

Title (1): A Theory of Definite Descriptions for Modal Logic
Time (1): 2:00 to 3:00 pm
Speaker (1): Nils Kürbis (Bochum)

Abstract (1): I’ll present a theory of definite descriptions in positive free logic, where definite descriptions ‘the F’ are formalised as in the context of complete sentences ‘The F is G’ by a binary quantifier as Ix(F, G). Formalised in natural deduction or sequent calculus, the theory satisfies certain proof-theoretic requirements demanded by proof theoretic semantics. Thus the meaning of I can be taken to be defined by its rules of inference. Positive free logic has been fruitfully applied in quantified modal logic. So I’ll consider what happens when modal operators are added. It turns out that the semantic clauses for Ix(F, G) are exactly those of Fitting and Mendelsohn (First Order Modal Logic, 2nd edition, Springer 2023), except that they formalise ‘The F is G’ by the iota operator for ‘the’ and the lambda for predicate abstraction to mark scope. I’ll end the talk with a brief comparison between the two systems.

Title (2): Solving a New Paradox of Deontic Logic (and a dozen other paradoxes) with RNmatrices for MC-based Modal Logics
Time (2): 3:00 to 4:00 pm
Speaker (2): Heinrich Wansing (Bochum) [joint work with Daniel Skurt (Bochum)]

Abstract (2): In this paper, we present RNmatrices (restricted non-deterministc matrices) for normal and non-normal modal expansions of the material connexive logic MC. We introduce and solve a paradox of deontic logic that to the best of our knowledge has not yet been been discussed in the literature and that justifies the use of a connexive, and actually hyperconnexive, non-modal base logic.

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

77th Nankai Logic Colloquium

Nankai Logic Colloquium

5/19/2025 4:55:10

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon. Our speaker this week will be Michal Doucha from the Institute of Mathematics, Czech Academy of Sciences. This talk will take place this Friday, May 23rd, from 4pm to 5pm (UTC+8, Beijing time).

Title: Generic actions of free groups on the Cantor space

Abstract: M. Hochman proved that the universal odometer is a generic minimal homeomorphism on the Cantor space. The aim of my talk is to generalize these results for actions of free groups. I will show how the generalization naturally splits into two directions:

(1) There is a notion of a universal odometer for free groups. Such odometers are not generic minimal actions for non-abelian free groups, however they are generic among those minimal actions that admit an invariant measure.

(2) The universal odometers can be also realized as inverse Fraisse limits of finite transitive actions. It turns out that if one takes instead the inverse Fraisse limit of sofic minimal shifts over a fixed free group, the result is then a generic minimal action on the Cantor space.

I will also mention why analogous results do not hold for Z^d. This is a part of joint work in progress with Julien Melleray and Todor Tsankov.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 77th Nankai Logic Colloquium-- Michal Doucha Time: 16:00pm, May. 23, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=92372646370

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

ESTS Colloquium today

Prague Set Theory Seminar

5/22/2025 5:09:06

Dear all, Forwarding the link for the online colloquium of the European Set Theory Society which will take place today at 17:00 CEST. Best, David -------- Forwarded Message -------- Subject: Link for ESTS Colloquium at 17:00 CEST this Thursday Date: Wed, 21 May 2025 14:07:40 +0200 From: European Set Theory Society Dear members, The zoom information for tomorrow's ESTS colloquium is https://tuwien.zoom.us/j/66562462164?pwd=xy3MJCp8uWjeoASXZOb0tYLq65hJDa.1 Meeting-ID: 665 6246 2164; Passwort: 18NGuaU0 Tishe date and time is Thursday, 22 May, at 17:00 central European summer time with the participants – Andrew Marks , University of California, Los Angeles – Grigor Sargsyan , Institute of Mathematics of the Polish Academy of Sciences – Dima Sinapova , Rutgers University Best wishes, Chris Lambie-Hanson, Sandra Müller, Philipp Schlicht and Zoltan Vidnyánszky (for the board of the ESTS) On 18/05/2025 21:59, David Chodounsky wrote: > Dear all, > > The seminar meets on Wednesday May 21st at 11:00 in the Institute of > Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. > > There will be a couple of other things which might be of interest: > Sean Cox will speak on Monday May 19th at the Algebra seminar, see here > https://www.mff.cuni.cz/cs/math/ka/akce/seminare/algebraicky-seminar > > The Fifth European Set Theory Colloquium (online) will take place on > Thursday May 22nd on Thursday, 22 May at 17:00 CETS, details here: > https://ests.wordpress.com/panel-discussions/ > > > Program (Wednesday): Adam Morawski -- The Rudin-Blass Ordering of Measures > > Finitely additive measures on omega can be viewed as a generalisation of > ultrafilters. The talk will focus on combinatorics of measures based on > methods used for ultrafilters -- in particular surrounding the Rudin- > Blass and Rudin-Keisler orderings. It is well known that Q-points are > exactly those ultrafilters that are Rudin-Blass minimal. It turns out > that this is not exactly the case for measures. I will introduce the > notion of Q-measures together with basic properties and provide a > construction of a Rudin-Blass minimal measure which is not Q (and is far > from it). > Results mentioned in the talk are fruits of joint work with P. > Borodulin-Nadzieja, A. Martinez-Celis and J. Świerczyńska. > > > Best, > David

Wednesday seminar

Prague Set Theory Seminar

5/26/2025 5:13:23

Dear all, The seminar meets on Wednesday May 28th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jindřich Zapletal -- Balanced forcing in geometric view Five years ago, with Paul Larson we developed the theory of balanced forcing as a flexible tool for independence results in choiceless set theory. I will present an axiomatization of the method which erases the methodological difficulties of this work and stresses its relationship with geometric model theory. Best, David

78th Nankai Logic Colloquium

Nankai Logic Colloquium

5/26/2025 9:43:15

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon. Our speaker this week will be Aleksandra Kwiatkowska from the University of Münster and the University of Wrocław. This talk will take place this Friday, May 30th, from 4pm to 5pm (UTC+8, Beijing time).

Title: Two-sorted ultrametric spaces via the Fraïssé construction

Abstract: I start with an overview of the Fraïssé theory, and next I introduce a particular two-sorted ultrametric space obtained via such a construction. This space will be universal for all countable two-sorted ultrametric spaces, and unlike with classical ultrametric spaces, we do not have to restrict to a countable set of real-valued distances. Furthermore, I discuss its automorphism group, in particular the existence of a comeager conjugacy class and non-existence of a generic pair. The talk will be based on an ongoing joint work with Bartoš, Kubiś, and Malicki.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 78th Nankai Logic Colloquium-- Aleksandra Kwiatkowska Time: 16:00pm, May. 30, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=91363113658

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

UPDATE - This Week in Logic at CUNY

This Week in Logic at CUNY

5/26/2025 9:50:25

Hi everyone,

Please note that last week's talk in the New York Category Theory Seminar was rescheduled to this Wednesday - details below.

All the best,

Jonas

- - - - Wednesday, May 28, 2025 - - - -

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: Thiago Alexandre.
Date and Time: Wednesday May 28, 2025, 4:00 - 5:30 PM. SPECIAL TIME! ZOOM TALK! (contact Noson Yanofsky for zoom link)
Title: Topological Derivators --- Part two.

Abstract: In this second part, I begin by recalling the axioms of topological derivators and presenting some elementary consequences of these axioms. Following this, I explain how topological derivators can be constructed by sheafifying homotopy theories. I conclude with the deepest theorem I have obtained in the theory of topological derivators, which provides strong evidence for Grothendieck’s conjecture: if a derivator can be extended to a topological derivator, then this extension is essentially unique.

MLTCS colloquium and Wednesday seminar

Prague Set Theory Seminar

5/30/2025 5:48:10

Dear all, Due to illness, The MLTCS Colloquium is postponed by a week, for Monday June 9th (same time and place). The Wednesday seminar should meet next week as scheduled. Best, David On 29/05/2025 10:58, David Chodounsky wrote: > Dear all, > > There will be two events next week. > On Monday June 2nd, 16:00 we will meet for the Colloquium of the MLTCS > department, Institute of Mathematics CAS, Zitna 25, blue lecture hall, > ground floor, rear building. > After the colloquium we will go for a drink. > > The seminar meets on Wednesday June 4th at 11:00 in the Institute of > Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. > > > Program Monday: > Chris Lambie-Hanson -- Inner model theory, from Gödel to Ultimate L > > We will present an overview of the mathematical and philosophical > underpinnings of the field of inner model theory and some of the > highlights of its almost 100-year history, beginning with Gödel's > constructible universe, passing through the remarkable results from the > 1980s connecting large cardinals with determinacy axioms, and ending > with an extended discussion of Woodin's Ultimate L program and its > vision for the future of set theory. > > > Program Wednesday: > Raúl Momblona -- Undecidability of the Whitehead Problem > > Is every Whitehead group free? This famous question by Whitehead was > showed to be independent of ZFC by Saharon Shelah in 1974. This talk > will review Shelah's solution using some arguments by Paul Eklof. > The talk is based on my master's thesis work. > > > Best, > David

MLTCS colloquium and Wednesday seminar

Prague Set Theory Seminar

5/29/2025 4:58:05

Dear all, There will be two events next week. On Monday June 2nd, 16:00 we will meet for the Colloquium of the MLTCS department, Institute of Mathematics CAS, Zitna 25, blue lecture hall, ground floor, rear building. After the colloquium we will go for a drink. The seminar meets on Wednesday June 4th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program Monday: Chris Lambie-Hanson -- Inner model theory, from Gödel to Ultimate L We will present an overview of the mathematical and philosophical underpinnings of the field of inner model theory and some of the highlights of its almost 100-year history, beginning with Gödel's constructible universe, passing through the remarkable results from the 1980s connecting large cardinals with determinacy axioms, and ending with an extended discussion of Woodin's Ultimate L program and its vision for the future of set theory. Program Wednesday: Raúl Momblona -- Undecidability of the Whitehead Problem Is every Whitehead group free? This famous question by Whitehead was showed to be independent of ZFC by Saharon Shelah in 1974. This talk will review Shelah's solution using some arguments by Paul Eklof. The talk is based on my master's thesis work. Best, David

KGRC Set Theory talk June 5

Kurt Godel Research Center

5/30/2025 11:33:29

KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, June 5, 11:30am--1:00pm, hybrid mode "Axiomatizing balanced forcing" J. Zapletal (U of Florida, Gainesville, US) Almost 10 years ago, with Paul Larson we developed the method of balanced forcing for consistency results in $\mathsf{ZF}$+$\mathsf{DC}$ In this talk, I will provide a novel axiomatization of the method, which is much less technical and more general. The parallels with geometric model theory become readily apparent. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to Vera Fischer vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, June 5, 3:00pm--3:50pm, hybrid mode "Cohomology of amalgamation diagrams" J. Zapletal (U of Florida, Gainesville, US) I define amalgamation diagram problems for models of set theory. I show how answers to such problems can lead to independence results in set theory. For some amalgamation diagram problems, their resolution amounts to calculating cohomology groups of certain natural cochain complexes. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to Matthias Aschenbrenner matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recording available so far from the Logic Colloquium: May 22: Y. Paresse (U of Hertfordshire, UK), "Semigroups Of Generalised Symmetries" https://ucloud.univie.ac.at/index.php/s/i7NgGeMGyACCEwq Video recording available so far from the Set Theory Seminar: May 22: W. Chan (TU Wien), "Infinite Cardinal Exponentiation III" https://ucloud.univie.ac.at/index.php/s/6mCrkfnebNkJMbz -- Kurt Gödel Research Center - Logic Group Faculty of Mathematics University of Vienna Kolingasse 14-16 1090 Vienna, Austria +43 (0) 1 / 4277-50501 https://kgrc.univie.ac.at

79th Nankai Logic Colloquium

Nankai Logic Colloquium

6/2/2025 10:41:39

Hello everyone,

This week will be the last Nankai Logic Colloquium of this semester. Our speaker this week will be Tomás Ibarlucía from the Université Paris Diderot. This talk will take place this Friday, June 6th, from 4pm to 5pm (UTC+8, Beijing time).

Title: Extremal decomposition and the Bauer–Poulsen dichotomy for simplicial affine theories

Abstract: I will present two results concerning simplicial theories in affine logic, i.e., the fragment of continuous logic in which the connectives are restricted to linear combinations and the constants.

As I will explain, type spaces in affine logic form compact convex sets, and a theory is called simplicial if all of its type spaces are Choquet simplices. It turns out that many important examples of affine theories are simplicial, including the theory of measure-preserving systems of a countable group, the theory of tracial von Neumann algebras, and the affine parts of many classical and continuous first-order theories.

After introducing the necessary preliminaries, I will discuss two major facts about simplicial theories:

Extremal decomposition: Every model of a simplicial theory can be written as a direct integral of extremal models.

Dichotomy theorem: every complete simplicial theory is either a Bauer theory or a Poulsen theory.

Based on joint work with Itaï Ben Yaacov and Todor Tsankov.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 79th Nankai Logic Colloquium-- Tomás Ibarlucía Time: 16:00pm, Jun. 6, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 477893 Link: https://zoom.us/j/3474053484?pwd=PZbb2KbpjHihE8QiaaBsTCMd2xsCca.1&omn=93294942532

Set Theory Seminar

Kolingasse 14--16, 1090, 1st floor, SR 10,

Thursday, June 16, 11:30am--1:00pm, hybrid mode

"Forcing with symmetric side conditions of models of two types"

C. Gallart Rodriguez (U Wien)

In this talk, I will give an introduction to the technique of forcing with side conditions and present some of the results obtained using the recently introduced symmetric matrices of models of two types.

The idea of adding systems of countable models as side conditions has been exploited extensively by Todorčević to build forcing notions that preserve cardinals and obtain consequences of forcing axioms at the level of the first uncountable cardinal.

The addition of models of a second type in recent work of Neeman, Asperó-Mota, Veličković, and others has proven to be very effective in pushing these results one cardinal higher, but most importantly, it has opened the door to obtaining consistent high analogs of classical strong forcing axioms.

Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at.

Please direct any questions about this talk to Vera Fischer vera.fischer@univie.ac.at.

* * * * * * * * *

Logic Colloquium

Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11,

Thursday, June 26, 3:00pm--3:50pm, hybrid mode

"Two complexity results"

Z. Vidnyánszky (Eötvös Loránd U, Budapest, HU)

The characterization of hyperfinite equivalence relations is a major open problem of descriptive set theory. A similarly notorious open problem is whether every hyper-hyperfinite equivalence relation is hyperfinite.

In this talk, I will show that, perhaps surprisingly, a negative answer to the latter implies a negative answer to the former. I will also discuss a recent development connecting Borel amenability to complexity.

Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at.

Please direct any questions about this talk to Matthias Aschenbrenner matthias.aschenbrenner@univie.ac.at.

* * * * * * * * *

Video recording available so far from the Logic Colloquium:

June 12 : V. Disarlo (IST, Klosterneuburg): "The model theory of the curve graph".

https://ucloud.univie.ac.at/index.php/s/2QanH7Eia9eYqzB

Video recording available so far from the Set Theory Seminar:

10/12/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Oct 13, 2025 - - - -

Rutgers Logic Seminar
Monday October 13, 3:30pm, Rutgers University, Hill 705
Riley Thornton, CMU

- - - - Tuesday, Oct 14, 2025 - - - -

- - - - Wednesday, Oct 15, 2025 - - - -

- - - - Thursday, Oct 16, 2025 - - - -

- - - - Friday, Oct 17, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 17, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)

Calliope Ryan-Smith, University of Leeds
The Axiom of Extendable Choice

The Partition Principle (PP) states that if there is a surjection A to B then there is an injection B to A. While this is an immediate consequence of the Axiom of Choice (AC), the question of if PP implies AC is one of the longest-standing open questions in set theory. Partial results regarding this come to us from many sources, including a theorem of Pincus that tells us that if 'for all ordinals A and all sets B, if there is a surjection B to A then there is an injection A to B' implies AC for well-orderable families of sets. We shall dissect this and related results, looking into the history of the structure of the cardinals in choiceless models and following the throughline to modern research on eccentric sets and the structure of cardinals as a partial order.

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

Hans Schoutens, CUNY
Can categories categorize the theories of model-theory?

I want to argue that when knowing the model-theory of categories, you kind of know the model-theory of any structure. As the ? at the end of the title suggests, some of this is still speculative.

It is easy to see a category as a first-order structure in the two-sorted language (for objects and morphisms) of categories; a little less to do this foundationally correct (I have given a talk a way back in which I ignored these issues, but I will correct this in the talk, although not mentioning them in this abstract). Now, to any theory T in some first-order language L, we can associate a theory in the language of categories, cat(T), which reflects this theory: the models of cat(T) are isomorphic (as categories) with subcategories of the category Mod(T) of models of T. In fact, any category that is elementary equivalent with Mod(T) is a sub-model of the latter.

This translation from T into cat(T)---from an arbitrary signature to a fixed one---is still mysterious, and as of now, I only know a very few concrete cases. A key role seems to be played by the theory FO, consisting of all sentences in the language of categories which hold in each category of L-structures, for all possible languages L. But I do not even know yet a full axiomatization of FO.

Next Week in Logic at CUNY:

- - - - Monday, Oct 20, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 20, 2-4pm (NY time)
Room: Graduate Center Room 8203

Eno Agolli (CUNY).
Title: All counterpossibles are false

Abstract: Counterpossibles are conditionals with impossible antecedents. All analyses of conditionals today agree that some counterpossibles are true. In this paper, I advance — to my knowledge for the first time — absurdism, the view that all counterpossibles are false. I do that in two steps. First, I show that there exists indeed an alternative analysis of conditionals which entails absurdism and which is well-motivated. The alternative analysis construes conditionals as plural definite descriptions of possible worlds and it is motivated by an impressively thoroughgoing parallelism between conditionals and definite plurals. Second, I show that absurdism itself is independently motivated, as it provides desirable logical results, a better rationale for positing pragmatic repair for counterpossibles, and ties in with a contemporary current of general skepticism toward counterfactuals.

Rutgers Logic Seminar
Monday October 20, 3:30pm, Rutgers University, Hill 705

Patrick Lutz, UC Berkeley

- - - - Tuesday, Oct 21, 2025 - - - -

- - - - Wednesday, Oct 22, 2025 - - - -

New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: Amartya Shekhar Dubey, National Institute of Science Education and Research.

Date and Time: Wednesday October 22, 2025, 2:00 - 3:00 PM. New York time. ZOOM TALK (Contact N. Yanofsky for link)

Title: Unital k-restricted Infinity Operads.

Abstract: The goal is to understand unital \infty-operads by their arity restrictions. Given k \geq 1, we develop a model for unital k-restricted \infinty-operads, which are variants of \infinity-operads with (\leq k)-arity morphisms, as complete Segal presheaves on closed k-dendroidal trees built from corollas with valence \leq k. Furthermore, we prove that the restriction functors from unital \infty-operads to unital k-restricted \infty-operads admit fully faithful left and right adjoints by showing that the left and right Kan extensions preserve complete Segal objects. Varying k, the left and right adjoints give a filtration and a co-filtration for any unital \infty-operads by k-restricted \infty-operads. This is joint work with Yu Leon Liu.

- - - - Thursday, Oct 23, 2025 - - - -

- - - - Friday, Oct 24, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 24, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)

Bartosz Wcisło University of Gdańsk

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

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KGRC talks on October 15, 16, and 17

Kurt Godel Research Center

10/10/2025 4:15:30

KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14 – 16, 1090, 1st floor, SR 10 Thursday, October 16, 11:30 am – 1:00 pm “Ladders and Squares” L. Notaro (U Wien) Given a positive integer $k$, a $k$-ladder is a lower-finite lattice whose elements have at most $k$ lower covers. In 1984, Ditor asked whether for every $k$ there is a $k$-ladder of cardinality $\aleph_{k-1}$. We show that this question has a positive answer under the axiom of constructibility. Please direct any questions about this talk to Vera Fischer (vera.fischer@univie.ac.at). If you would like to attend online, please send an email to info@logic.univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11 Thursday, October 16, 3:00 pm – 3:50 pm “Local Hanf-Tarski numbers” J. Aguilera (TU Wien) We say that a cardinal $k$ is a local Hanf-Tarski number of a logic $L$ if every model $\mathcal{M}$ of an $L$-sentence $\phi$ of size $k$ can be extended to models of $\phi$ of arbitrarily large size. In this talk, we present various results concerning local Hanf-Tarski numbers and how they differ from global Hanf-Tarski numbers (for which $\mathcal{M}$ is allowed to have size greater than or equal to $k$) and from classical Hanf numbers. Please direct any questions about this talk to Matthias Aschenbrenner (matthias.aschenbrenner@univie.ac.at). If you would like to attend online, please send an email to info@logic.univie.ac.at. * * * * * * * * * Online PhD defense The defense takes place online; it will also be streamed in Kolingasse 14 – 16, 1090, 2nd floor, SR 18 Friday, October 17, 4:00 pm – 5:00 pm “Definable Witnesses” J. M. Millhouse (U Vienna) The abstract of this PhD thesis is available at https://ucloud.univie.ac.at/index.php/s/cG9HLX6eiGNXgT6 If you would like to attend online, please send an email to info@logic.univie.ac.at. * * * * * * * * New video recording available from the Logic Colloquium: October 9: R. Honzik (Charles U, Prague, DZ) “Compactness in mathematics” https://ucloud.univie.ac.at/index.php/s/8S8nqS8HX2gAMWb --- Kurt Gödel Research Center Logic Group University of Vienna - Faculty of Mathematics Kolingasse 14-16 1090 Vienna Austria +43 (0) 1 / 4277-50501 https://kgrc.univie.ac.at

Wednesday seminar (location change) and MLTCS Colloquium

Prague Set Theory Seminar

10/8/2025 8:58:48

Dear all, The Colloquium of the MLTCS Department meets on Monday October 13th in the Institute of Mathematics CAS, Zitna 25, blue lecture hall, ground floor, rear building. We meet at 16:00 for coffee and cookies; the lecture will start 16:15. We will go to for a drink afterwards. The seminar meets on Wednesday October 15th at 11:00 in the Institute of Mathematics CAS, Zitna 25, blue lecture hall, ground floor, rear building. NOTE THE LOCATION CHANGE The conference Horizons: Conference in Honour of Petr Vopěnka will take place during October 24--25 in Akademicke konferencni centrum, Husova 4a, Prague, Czech Republic. There is no conference fee but registration is required. https://www.cts.cuni.cz/index.php?m=43&akce=1861&lang=en Program (Monday): Pavel Hubacek -- Polynomial Commitments: Foundations, Frontiers, and Open Problems Polynomial commitments, introduced by Kate, Zaverucha, and Goldberg (ASIACRYPT 2010), are a core primitive in practical cryptographic proof systems. This talk presents the main schemes, clarifies security formulations and modeling pitfalls, and surveys efficiency trade-offs in state-of-the-art designs. I conclude with concrete open problems and directions. Program (Wednesday): Rosemary A. Bailey and Peter J. Cameron -- Permutation groups, lattices and orthogonal block structures The story began when our coauthor Marina was doing an undergraduate research internship under Peter's supervision. We were studying transitive but imprimitive permutation groups through their invariant equivalence relations, and were looking at the case where the equivalence relations commute; in our shared office, Rosemary overheard our conversation, and said, "Statisticians know about those things; we call them orthogonal block structures." An orthogonal block structure (OBS) is a lattice of commuting uniform equivalence relations. These are combinatorial objects which may have trivialautomorphism group. Latin squares provide many examples of OBSs. We will discuss the history of how OBSs arose in experimental design. A better behaved special case occurs when the lattice is distributive; these are called poset block structures. They always have a large automorphism group, a generalised wreath product of symmetric groups, described by a poset with a set attached at each of its points. Our main results are a proof that a group preserving a poset block structure is contained in a generalised wreath product of permutation groups defined from the action (an extension of the Krasner-Kaloujnine theorem), and that a generalised wreath product over a poset is the intersection of the iterated wreath products of the same groups over all linear extensions of the poset. In terms of the group operation, so that the graph is invariant under all automorphisms of the group. The classical example is the commuting graph of a group, defined by Brauer and Fowler in a seminal paper in 1955. There has been a lot of work on this topic recently. My interests are mainly in how the theories of groups and graphs can help one another. Some of the questions I will address are - finding new results about groups; - characterising important classes of groups using graphs; - recognising graphs obtained from groups and, if possible, reconstructing the groups; - finding some beautiful graphs. Recently I have widened the investigation to simplicial complexes defined on groups; I will present a small amount of new material and some open problems on this also. Best, David

This Week in Logic at CUNY

10/5/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Oct 6, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 6, 2-4pm (NY time)
Room: Graduate Center Room 8203
Juliette Kennedy (Helsinki).
Title: How first order is first order logic?

Abstract: Fundamental to the practice of logic is the dogma regarding the first order/second order logic distinction, namely that it is ironclad. Was it always so? The emergence of the set theoretic paradigm is an interesting test case. Early workers in foundations generally used higher order systems in the form of type theory; but then higher order systems were gradually abandoned in favour of first order set theory—a transition that was completed, more or less, by the 1930s. In this talk I will look at first order logic from various points of view, arguing that the distinction between first order and higher order logics, such as second order logic, is somewhat context dependent. From the philosophical or foundational point of view this complicates the picture of first order logic as a canonical logic.

- - - - Tuesday, Oct 7, 2025 - - - -

- - - - Wednesday, Oct 8, 2025 - - - -

- - - - Thursday, Oct 9, 2025 - - - -

- - - - Friday, Oct 10, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 10, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)

Dan Hathaway, University of Vermont
On Absoluteness Between V and HOD

We put together Woodin's $Σ 21$ basis theorem of $A D +$ and Vopěnka's theorem to conclude the following: If there is a proper class of Woodin cardinals, then every $(Σ 21) u B$ statement that is true in V is true in HOD. Moreover, this is true even if we allow a certain parameter. We then show that stronger absoluteness cannot be implied by any large cardinal axiom consistent with the axiom V = Ultimate L.

Logic Workshop
CUNY Graduate Center
Friday, October 10, 2:00pm-3:30pm, Room 6417
Philip Scowcroft, Wesleyan University
Injective simple dimension groups

A dimension group is a partially ordered Abelian group whose partial order is isolated and directed and has the Riesz interpolation property. A dimension group is simple just in case it has no nontrivial ideals, ideals being directed convex subgroups. By concentrating on the behavior of positive formulas in simple dimension groups, this talk will reveal a well-behaved part of their model theory.

Next Week in Logic at CUNY:

- - - - Monday, Oct 13, 2025 - - - -

Rutgers Logic Seminar
Monday October 13, 3:30pm, Rutgers University, Hill 705
Riley Thornton, CMU

- - - - Tuesday, Oct 14, 2025 - - - -

- - - - Wednesday, Oct 15, 2025 - - - -

- - - - Thursday, Oct 16, 2025 - - - -

- - - - Friday, Oct 17, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 17, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)

Calliope Ryan-Smith, University of Leeds

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

Hans Schoutens, CUNY
Can categories categorize the theories of model-theory?

I want to argue that when knowing the model-theory of categories, you kind of know the model-theory of any structure. As the ? at the end of the title suggests, some of this is still speculative.

It is easy to see a category as a first-order structure in the two-sorted language (for objects and morphisms) of categories; a little less to do this foundationally correct (I have given a talk a way back in which I ignored these issues, but I will correct this in the talk, although not mentioning them in this abstract). Now, to any theory T in some first-order language L, we can associate a theory in the language of categories, cat(T), which reflects this theory: the models of cat(T) are isomorphic (as categories) with subcategories of the category Mod(T) of models of T. In fact, any category that is elementary equivalent with Mod(T) is a sub-model of the latter.

This translation from T into cat(T)---from an arbitrary signature to a fixed one---is still mysterious, and as of now, I only know a very few concrete cases. A key role seems to be played by the theory FO, consisting of all sentences in the language of categories which hold in each category of L-structures, for all possible languages L. But I do not even know yet a full axiomatization of FO.

- - - - Other Logic News - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Wednesday seminar and MLTCS Colloquium

Prague Set Theory Seminar

10/4/2025 14:35:16

Dear all, The seminar meets on Wednesday October 8th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. On Monday October 13th we will have a Colloquium of the MLTCS department with Pavel Hubacek as the speaker, talk title TBA. The colloquium will meet in the Institute of Mathematics CAS, Zitna 25, blue lecture hall, ground floor, rear building at 16:00 for coffee and cookies; the lecture will start 16:15. We will go to for a drink afterwards. Program (seminar October 8): Mariaclara Ragosta -- An introduction of nonstandard methods in Arithmetic Ramsey Theory Arithmetic Ramsey Theory studies which properties of subsets of the naturals are ``indestructible'' under finite partitions. For instance, Schur's Theorem (1916) states that for every finite coloring of N there exists a monochromatic triple a, b, a+b. Several decades later, in 1974, Hindman showed, in the same setting, the existence of a unique infinite sequence such that all finite sums are monochromatic. Hindman's original proof was completely combinatorial and extremely complicated. A year later, Galvin and Glazer proved, by using ultrafilters, that the same result holds for every associative operation. Furthermore, their proof was particularly short and elegant, so that Hindman himself was very impressed with it and began to use ultrafilters in his research. During my studies, at some point, I also met ultrafilters and fell in love with them. As well as Hindman, I realised their usefulness in Ramsey Theory and proved my first theorems in this field of research exploiting their strong properties. Later, I had the opportunity to learn about nonstandard methods. Ultrafilters are complicated objects, since they are subsets of the set of all subsets of the naturals. Who works with them is aware that the only ultrafilters that are easy to deal with are the principal ones, because they are precisely those that can be represented, and in some sense identified, with natural numbers. The problem is that principal ultrafilters are trivial and, basically, useless. Nonstandard methods allow to treat all ultrafilters as they were ``principal'', but generated by hypernatural numbers, a set of numbers that includes N and somehow behaves similarly, but is much richer than it. Each ultrafilter is generated by some hypernatural number, and properties of generators precisely correspond to sets belonging to that ultrafilter. For instance, the ultrafilter contains even numbers if and only if all generators are even. The aim of this talk is to introduce nonstandard methods and let people appreciate, with some examples, this very promising approach in Arithmetic Ramsey Theory. Best, David

KGRC talks October 9

Kurt Godel Research Center

10/3/2025 17:27:16

KGRC/Institute of Mathematics invites you to the following 2 talks:
(updates at https://kgrc.univie.ac.at/eventsnews/)

Set Theory Seminar
Kolingasse 14 – 16, 1090, 1st floor, SR 10
Thursday, October 9, 11:30 am – 1:00 pm, hybrid mode

“Ranked Forcing and the Structure of Borel Hierarchies”
N. Chapman (TU Wien)

The structural study of the Borel hierarchy on topological spaces is a foundational goal of descriptive set theory. By an early result of the field, we know that there exist universal sets at each level $\alpha < \omega_1$ of the Borel hierarchy on the Baire space $\omega^\omega$, hence the order of this hierarchy, i.e. the first ordinal $\alpha$ at which every Borel set has been generated, attains the maximal possible value of $\omega_1$. However, there are other subspaces of $\omega^\omega$ where this hierarchy is shorter; take for example any countable space, on which every Borel subset must be $\Sigma^0_2$.

The topic of this talk is a framework for the surgical alteration of the complexity of the Borel hierarchy on subspaces of $\omega^\omega$, pioneered by A. Miller. We will discuss Miller's notion of $\alpha$-forcing, which allows for either collapsing or increasing the length of the Borel hierarchy, as well as the proof ideas behind some preservation theorems necessary to do so. In the second part of the talk, we will delve into recent developments in this area, such as an extension of the framework to the field of generalized descriptive set theory of an uncountable cardinal $\kappa = \kappa^{<\kappa}$ or the study of the $\lambda$-Borel subsets of $\kappa^\kappa$ for $\lambda > \kappa$, with a particular emphasis on the case $\lambda = \omega_1$ and $\kappa = \omega$. We will give several examples of models constructed using this method in both the classical case of $\omega$ and the generalized case of an uncountable $\kappa$. Lastly, we will discuss some limitations of the technique and directions for future work.

Please direct any questions about this talk to Vera Fischer (vera.fischer@univie.ac.at).

If you would like to attend online, please send an email to info@logic.univie.ac.at.

* * * * * * * * *

Logic Colloquium
Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11,
Thursday, October 9, 3:00 pm – 3:50 pm, hybrid mode

“Compactness in mathematics”
R. Honzík (Charles U, Prague, CZ)

We discuss some well-known compactness principles for uncountable structures of small regular sizes ($\omega_n$ for $2 \le n<\omega$, $\aleph_{\omega+1}$, $\aleph_{\omega^2+1}$, etc.), consistent from weakly compact (the size-restricted versions) or strongly compact or supercompact cardinals (the unrestricted versions). For the exposition, we divide the principles into logical principles, which are related to cofinal branches in trees and more general structures (various tree properties), and mathematical principles, which directly postulate compactness for structures like groups, graphs, or topological spaces (for instance, countable chromatic and color compactness of graphs, compactness of abelian groups, $\Delta$-reflection, Fodor--type reflection principle, and Rado's Conjecture).

We also focus on \emph{indestructibility}, or \emph{preservation}, of these principles in forcing extensions. While preservation adds a degree of robustness to such principles, it also limits their provable consequences. For example, some well-known mathematical problems such as Suslin Hypothesis, Whitehead's Conjecture, Kaplansky's Conjecture, and the categoricity of $\omega_1$-dense subsets of the reals (Baumgartner's Axiom), are independent from some of the strongest forms of compactness at $\omega_2$. This is a refined version of Solovay's theorem that large cardinals are preserved by small forcings and hence cannot decide many natural problems in mathematics. Additionally, we observe that Rado's Conjecture plus $2^\omega = \omega_2$ is consistent with the negative solutions, i.e. as they hold in $V =L$, of some of these conjectures (Suslin's, Whitehead's, and Baumgartner's axiom), verifying that they hold in suitable Mitchell models.

Finally, we comment on whether the compactness principles under discussion are good candidates for axioms. We consider their consequences and the existence or non-existence of convincing unifications (such as Martin's Maximum or Rado's Conjecture). This part is a modest follow-up to the articles by Foreman "Generic large cardinals: new axioms for mathematics?'' and Feferman et al. "Does mathematics need new axioms?''.

Please direct any questions about this talk to Matthias Aschenbrenner (matthias.aschenbrenner@univie.ac.at).

If you would like to attend online, please send an email to info@logic.univie.ac.at.

No Nankai Logic Colloquium until late October

Nankai Logic Colloquium

9/29/2025 11:56:23

Hello everyone,

Due to national holidays in China, there is no Nankai Logic Colloquium talk this week. And since there are two conferences for the following two weeks after national holidays, we will resume our regular schedule on October 24th.

Thank you for your understanding!

Best regards,

Wei

This Week in Logic at CUNY

9/28/2025 22:30:00

- - - - Monday, Sep 29, 2025 - - - -

Rutgers Logic Seminar
Monday September 29, 3:30pm, Rutgers University, Hill 705
Tom Benhamou, Rutgers
On the cofinality of ultrafilters

Logic and Metaphysics Workshop
Date: Monday, September 29, 2-4pm (NY time)
Room: Graduate Center Room 8203
Will Nava (NYU)
Title: Horizontal Fregeanism

Abstract: Fregeanism is the view that primitive expressive roles correspond to metaphysically distinct kinds. For example: singular terms refer to objects whereas predicates ascribe properties, and properties are not objects. Fregeanism is typically paired with the assumption that properties cannot apply to properties of the same ‘rank’, thereby generating a hierarchical space of metaphysical kinds (and corresponding expressive roles). I propose an alternative horizontal Fregeanism, on which properties can self-apply, so no hierarchy is introduced. The metaphysical kinds are just objects, n-place properties (for each n), and propositions. In this talk, I’ll defend horizontal Fregeanism over the hierarchical alternative. I’ll also argue that the view calls for a novel syntax; one that allows direct self-application (i.e. sentences of the form FF), while still respecting the distinction between objects, properties, and propositions. I will present this syntax, along with an attractive logic formulated in it.

- - - - Tuesday, Sep 30, 2025 - - - -

- - - - Wednesday, Oct 1, 2025 - - - -

- - - - Thursday, Oct 2, 2025 - - - -

- - - - Friday, Oct 3, 2025 - - - -

SPECIAL EVENT: Some problems of entailment – A workshop on relevance logic

The Logic and Metaphysics Workshop

Date: Friday, October 3, 9:30am-5:30pm (NY time)
Room: Graduate Center Room 8203

Program is available on the website.

Speakers:
Thomas Macaulay Ferguson (Rensselaer)
Kit Fine (NYU)
Shay Allen Logan (Kansas State)
Alexander Macswan (CUNY)
Shawn Standefer (NC State)
Yale Weiss (CUNY)
Daniel West (CUNY)

Set Theory Seminar
CUNY Graduate Center
Friday, October 3, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)
Eyal Kaplan, University of California, Berkeley
The number of normal measures, revisited

A central question in the theory of large cardinals was whether the existence of a model of ZFC with exactly two normal measures follows from the consistency of ZFC with a measurable cardinal. This was answered positively by a landmark theorem of Friedman and Magidor, whose proof masterfully combined advanced techniques in the theory of large cardinals, including generalized Sacks forcing, forcing over canonical inner models, coding posets, and nonstationary support iterations.

In this talk, we present a new and simpler proof of the Friedman-Magidor theorem. A notable feature of our approach is that it avoids any use of inner model theory, making it applicable in the presence of very large cardinals that are beyond the current reach of the inner model program. If time permits, we will also discuss additional applications of the technique: the construction of ZFC models with several normal measures but a single normal ultrapower; a nontrivial model of the weak Ultrapower Axiom from the optimal large cardinal assumption; and a generalization of the Friedman–Magidor theorem to extenders.

Next Week in Logic at CUNY:

- - - - Monday, Oct 6, 2025 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 6, 2-4pm (NY time)
Room: Graduate Center Room 8203
Juliette Kennedy (Helsinki).
Title: How first order is first order logic?

Abstract: Fundamental to the practice of logic is the dogma regarding the first order/second order logic distinction, namely that it is ironclad. Was it always so? The emergence of the set theoretic paradigm is an interesting test case. Early workers in foundations generally used higher order systems in the form of type theory; but then higher order systems were gradually abandoned in favour of first order set theory—a transition that was completed, more or less, by the 1930s. In this talk I will look at first order logic from various points of view, arguing that the distinction between first order and higher order logics, such as second order logic, is somewhat context dependent. From the philosophical or foundational point of view this complicates the picture of first order logic as a canonical logic.

- - - - Tuesday, Oct 7, 2025 - - - -

- - - - Wednesday, Oct 8, 2025 - - - -

- - - - Thursday, Oct 9, 2025 - - - -

- - - - Friday, Oct 10, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 10, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)

Dan Hathaway University of Vermont

Logic Workshop
CUNY Graduate Center
Friday, October 10, 2:00pm-3:30pm, Room 6417
Philip Scowcroft, Wesleyan University
Injective simple dimension groups

A dimension group is a partially ordered Abelian group whose partial order is isolated and directed and has the Riesz interpolation property. A dimension group is simple just in case it has no nontrivial ideals, ideals being directed convex subgroups. By concentrating on the behavior of positive formulas in simple dimension groups, this talk will reveal a well-behaved part of their model theory.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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KGRC talk September 30

Kurt Godel Research Center

9/26/2025 8:59:22

KGRC/Institute of Mathematics of the University of Vienna invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/) Set Theory Seminar Kolingasse 14–16, 1090, 1st floor, SR 10 Tuesday, September 30, 3:00 pm – 3:50 pm, hybrid mode “Ramsey property and madness” Y. Li (U Amsterdam, NL) We give an expository introduction of Schrittesser and Törnquist's result that under some weak choice principle, all sets having the Ramsey property implies that there is no infinite maximal almost disjoint family (MAD) family. In particular, this gives a proof that there is no MAD family in the Solovay Model. We also discuss how their result localizes in the projective hierarchy. Please direct any questions about this talk to Vera Fischer (vera.fischer@univie.ac.at). If you would like to attend online, please send an email to info@logic.univie.ac.at. ***** New video recording available from the Set Theory Seminar: September 25: L. Gardiner (U of Cambridge, UK) “Colouring copies of the rationals” https://ucloud.univie.ac.at/index.php/s/K2886zMZYwQ2Q6Y --- Kurt Gödel Research Center - Logic Group University of Vienna - Faculty of Mathematics Kolingasse 14-16 1090 Vienna Austria +43 (0) 1 / 4277-50501 https://kgrc.univie.ac.at -- Dr. Matteo Tommasini Kurt Gödel Research Center - Logic Group Faculty of Mathematics University of Vienna Tel. +43 - 1 - 4277 50719

81st Nankai Logic Colloquium

Nankai Logic Colloquium

9/22/2025 3:20:53

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the morning. Our speaker this week will be Joshua Frisch from the University of California San Diego. This talk will take place this Friday, September 26th, from 9am to 10am (UTC+8, Beijing time).

Title: Minimal Subdynamics: Descriptive ideas about Dynamical Questions

Abstract: Let be a countably infinite discrete group. A -flow (i.e., a nonempty compact Hausdorff space equipped with a continuous action of ) is called -minimal for a subset if the partial orbit is dense for every point . (When , we recover the usual notion of minimality.) Despite the simplicity of the definition, given a group , finding an -minimal dynamical system is typically quite difficult (in particular even when Γ is the free group and is a subgroup it was not previously known).

In this talk, I will discuss a very recent result on how to construct -minimal systems for any countable collection of infinite subsets simultaneously. Although the problem is purely dynamical, the techniques make heavy use of recent ideas from descriptive set theory. Indeed, once the main result is established, we can return to derive some non-obvious, purely Borel, corollaries. This is joint work with Anton Bernshteyn.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 81st Nankai Logic Colloquium--Joshua Frisch Time: 9:00am, September.26, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 796087 Link: https://zoom.us/j/3474053484?pwd=bCM3G3C479kilUmP0RuWimJ47XxaLG.1&omn=92934699209

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

This Week in Logic at CUNY

9/21/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Sep 22, 2025 - - - -

Rutgers Logic Seminar

Monday 3:30pm, Rutgers University, Hill 705

Cecelia Higgins, Rutgers
Measurable Brooks's Theorem for Directed Graphs

Logic and Metaphysics Workshop
Date: Monday, September 22, 2-4pm (NY time)
Room: Graduate Center Room 8203
Fernando Cano-Jorge (Otago).
Title: The heresies project

Abstract: In the late 90’s, Richard Sylvan and Jack Copeland advanced the idea that computability is logic relative and that the Church-Turing thesis is false. Sylvan called this The Heresies Project and at its core is the idea that couching computability theory on a paraconsistent logic can take us beyond the classically computable. In the first part of this talk, I provide a brief introduction to paraconsistent computability theory, distinguishing non-revisionary approaches vs. Sylvan and Copeland’s more radical proposal. In the second part of this talk, I discuss what is required to pursue The Heresies Project. I will focus on Robinson arithmetic based on Sylvan’s preferred logic, DK, and its ability to both represent all recursive functions and prove Gödel’s first incompleteness theorem. I conclude that one of the keys to The Heresies Project, i.e. using an inconsistent metatheory, seems to clash with the arithmetic’s capacity to capture all recursive functions.

- - - - Tuesday, Sep 23, 2025 - - - -

- - - - Wednesday, Sep 24, 2025 - - - -

- - - - Thursday, Sep 25, 2025 - - - -

- - - - Friday, Sep 26, 2025 - - - -

MAMLS Fall Fest 2025

The 2025 Rutgers MAMLS meeting will take place on Sept. 26-28 at Rutgers University, in New Brunswick, NJ. Talks begin at 3:30 pm on Friday, 10:00 am on Saturday, and 9:30 am on Sunday, ending Sunday at 12:30. For details and to register, please visit the website. Some travel support is available: enquire with Prof. Filippo Calderoni.

Paraconsistent computing workshop (Special Event)

The Logic & Metaphysics Workshop

CUNY G.C., Room 7113.08 (7th floor)

Friday, September 26, 2025, 11:00 am – 5:00 pm
Organizers: Eno Agolli & Yale Weiss (CUNY Graduate Center)
Speakers/Participants:

Fernando Cano-Jorge (University of Otago)
Thomas Macaulay Ferguson (Rensselaer Polytechnic Institute)
Graham Priest (CUNY Graduate Center)

The Logic and Metaphysics Workshop will meet on Friday, September 26th, from 11:00-5:00 in-person at the Graduate Center (Room 7113.08) for a workshop on Paraconsistent Computing. The program is available here.

Next Week in Logic at CUNY:

- - - - Monday, Sep 29, 2025 - - - -

Rutgers Logic Seminar

Monday September 29, 3:30pm, Rutgers University, Hill 705

Tom Benhamou, Rutgers
On the cofinality of ultrafilters

Logic and Metaphysics Workshop
Date: Monday, September 29, 2-4pm (NY time)
Room: Graduate Center Room 8203

Will Nava (NYU)
Title: Horizontal Fregeanism

Abstract: Fregeanism is the view that primitive expressive roles correspond to metaphysically distinct kinds. For example: singular terms refer to objects whereas predicates ascribe properties, and properties are not objects. Fregeanism is typically paired with the assumption that properties cannot apply to properties of the same ‘rank’, thereby generating a hierarchical space of metaphysical kinds (and corresponding expressive roles). I propose an alternative horizontal Fregeanism, on which properties can self-apply, so no hierarchy is introduced. The metaphysical kinds are just objects, n-place properties (for each n), and propositions. In this talk, I’ll defend horizontal Fregeanism over the hierarchical alternative. I’ll also argue that the view calls for a novel syntax; one that allows direct self-application (i.e. sentences of the form FF), while still respecting the distinction between objects, properties, and propositions. I will present this syntax, along with an attractive logic formulated in it.

- - - - Tuesday, Sep 30, 2025 - - - -

- - - - Wednesday, Oct 1, 2025 - - - -

- - - - Thursday, Oct 2, 2025 - - - -

- - - - Friday, Oct 3, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 3, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)

Eyal Kaplan, University of California, Berkeley
The number of normal measures, revisited

A central question in the theory of large cardinals was whether the existence of a model of ZFC with exactly two normal measures follows from the consistency of ZFC with a measurable cardinal. This was answered positively by a landmark theorem of Friedman and Magidor, whose proof masterfully combined advanced techniques in the theory of large cardinals, including generalized Sacks forcing, forcing over canonical inner models, coding posets, and nonstationary support iterations.

In this talk, we present a new and simpler proof of the Friedman-Magidor theorem. A notable feature of our approach is that it avoids any use of inner model theory, making it applicable in the presence of very large cardinals that are beyond the current reach of the inner model program. If time permits, we will also discuss additional applications of the technique: the construction of ZFC models with several normal measures but a single normal ultrapower; a nontrivial model of the weak Ultrapower Axiom from the optimal large cardinal assumption; and a generalization of the Friedman–Magidor theorem to extenders.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Wednesday seminar

Prague Set Theory Seminar

9/21/2025 13:52:33

Dear all, The seminar meets on Wednesday September 24th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There will be no seminar on Wednesday October 1st due to the offsite meeting of the Institute. Program: Jesús Alberto Soria Rojas -- Selective ultrafilters and idempotents with an application to choiceless set theory Continuing the study of ultrafilters from the perspective of the algebra in the Čech-Stone compactification of the natural numbers, and idempotent elements therein. We will present that, if p is a selective ultrafilter and G^p is the smallest family containing p and closed under Blass-Frolík sums and Rudin-Keisler images, then G^p contains no idempotent elements. These has the following interesting consequence: assuming a conjecture of Blass, in models of the form L(R)[p] where L(R) is a Solovay model (of ZF without choice) and p is a selective ultrafilter, there are no idempotent elements. In particular, the theory ZF plus the existence of a nonprincipal ultrafilter on the naturals does not imply the existence of idempotent ultrafilters, which answers a question of Di Nasso and Tachtsis (Proc. Amer. Math. Soc. 146, 397--411) that was also asked by Tachtsis (J. Symb. Log. 83, 557--571). This is joint work with David Fernández-Bretón and Jareb Navarro-Castillo. Best, David

KGRC talk September 25

Kurt Godel Research Center

9/19/2025 5:08:52

KGRC/Institute of Mathematics invites you to the following talk: (updates at https://kgrc.univie.ac.at /) Set Theory Seminar Kolingasse 14-16, 1090, 1st floor, SR10 Wednesday, September 25, 11:30am – 1:00pm, hybrid mode ”Colouring copies of the rationals” Lyra Gardiner (U Cambridge, UK) We demonstrate some results in the theory of infinite-exponent partition relations on linear orders and show that a certain relation of this type implies the failure of the choice principle KWP1. We then answer a question of Fatalini about an analogous result in the setting of graphs. This is a joint work with Thilo Weinert and Jonathan Schilhan. Please direct any questions about this talk to Vera Fischer (vera.fischer@univie.ac.at). -- Kurt Gödel Research Center - Logic Group University of Vienna - Faculty of Mathematics Kolingasse 14-16 1090 Vienna Austria +43 (0) 1 / 4277-50501 https://kgrc.univie.ac.at

UPDATE - This Week in Logic at CUNY

This Week in Logic at CUNY

9/17/2025 9:10:04

Hi everyone,

This evening's talk in the New York City Category Theory Seminar has been cancelled.

Best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Sep 15, 2025 - - - -

Rutgers Logic Seminar

Monday 4:30pm, Rutgers University, Hill 705 (NOTE SPECIAL TIME)

Moti Gitik, Tel-Aviv University
On some PCF configurations

- - - - Tuesday, Sep 16, 2025 - - - -

- - - - Wednesday, Sep 17, 2025 - - - -

New York City Category Theory Seminar

Department of Computer Science
Department of Mathematics

The Graduate Center of The City University of New York

Room 6496
Speaker: Sam McCrosson, Montana State University.
Date and Time: Wednesday September 17, 2025, 7:00 - 8:30 PM. ZOOM TALK.
Title: Using Microsupports to Detect and Describe Constructible Sheaves.

Abstract: Microlocal sheaf theory has been gaining popularity recently for its applications to symplectic geometry. In this talk, we’ll explore a more topological application of this subject: how the notion of the microsupport of a sheaf can be used to tell if a sheaf is “constructible,” i.e. locally constant on strata, and if so, what the coarsest stratification is with this property.

Versions of this result can be found as far back as Kashiwara and Schapira’s 1990 book “Sheaves on Manifolds” (which pioneered the subject of microlocal sheaf theory). Today, all sorts of generalizations are possible using schemes, \infty-categories, and other fancy machinery. This talk will focus on a particularly simple case: using 1-category theory and sheaves of sets on topological spaces to illustrate the key ideas with concrete examples.

- - - - Thursday, Sep 18, 2025 - - - -

- - - - Friday, Sep 19, 2025 - - - -

Logic Workshop
CUNY Graduate Center
Friday, September 19, 2:00pm-3:30pm, Room 6417

James Walsh, New York University

A theory satisfying a strong version of Tennenbaum's theorem

Tennenbaum's theorem states that no non-standard model of PA is computable. Hence, no unsound extension of PA has computable models. Pakhomov recently showed that this consequence of Tennenbaum's theorem is fragile; it depends on the signature in which PA is presented. In particular, there is a theory T such that (i) T is definitionally equivalent to PA (this is a strong form of bi-interpretability) and (ii) every consistent r.e. extension of T has a computable model. Pakhomov's techniques yield analogous results for ZF and other canonical systems. He asked whether there is a consistent, r.e. theory T such that no theory which is definitionally equivalent to T has a computable model. We answer this question with an ad hoc construction. This is joint work with Patrick Lutz.

Next Week in Logic at CUNY:

- - - - Monday, Sep 22, 2025 - - - -

Rutgers Logic Seminar

Monday 3:30pm, Rutgers University, Hill 705

Cecelia Higgins, Rutgers
Measurable Brooks's Theorem for Directed Graphs

Logic and Metaphysics Workshop
Date: Monday, April 4/7, 2-4pm (NY time)
Room: Graduate Center Room
Fernando Cano-Jorge (Otago).
Title: The heresies project

Abstract: In the late 90’s, Richard Sylvan and Jack Copeland advanced the idea that computability is logic relative and that the Church-Turing thesis is false. Sylvan called this The Heresies Project and at its core is the idea that couching computability theory on a paraconsistent logic can take us beyond the classically computable. In the first part of this talk, I provide a brief introduction to paraconsistent computability theory, distinguishing non-revisionary approaches vs. Sylvan and Copeland’s more radical proposal. In the second part of this talk, I discuss what is required to pursue The Heresies Project. I will focus on Robinson arithmetic based on Sylvan’s preferred logic, DK, and its ability to both represent all recursive functions and prove Gödel’s first incompleteness theorem. I conclude that one of the keys to The Heresies Project, i.e. using an inconsistent metatheory, seems to clash with the arithmetic’s capacity to capture all recursive functions.

- - - - Tuesday, Sep 23, 2025 - - - -

- - - - Wednesday, Sep 24, 2025 - - - -

- - - - Thursday, Sep 25, 2025 - - - -

- - - - Friday, Sep 26, 2025 - - - -

MAMLS Fall Fest 2025
The 2025 Rutgers MAMLS meeting will take place on Sept. 26-28 at Rutgers University, in New Brunswick, NJ. Talks begin at 3:30 pm on Friday, 10:00 am on Saturday, and 9:30 am on Sunday, ending Sunday at 12:30. For details and to register, please visit the website. Some travel support is available: enquire with Prof. Filippo Calderoni.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

80th Nankai Logic Colloquium

Nankai Logic Colloquium

9/15/2025 1:36:43

Hello everyone,

Welcome back! This week will be the first Nankai Logic Colloquium of the new semester. Our speaker this week will be Andy Zucker from the University of Waterloo. This talk will take place this Friday, September 19th, from 9am to 10am (UTC+8, Beijing time).

Title: Tameness, forcing, and the revised Newelski conjecture

Abstract: The revised Newelski conjecture asserts that for any group definable in an NIP structure, the automorphism group of its definable universal minimal flow is Hausdorff in the so-called "tau-topology." Recently, the countable case of the conjecture was proven by Chernikov, Gannon, and Krupinski using a deep result of Glasner, which provides a structure theorem for minimal metrizable tame flows. With this result, they prove that the Ellis group of a minimal metrizable tame flow (the automorphism group of a related flow) has Hausdorff tau-topology, and the conjecture for groups definable in countable NIP structures follows. We prove the revised Newelski conjecture in full by showing that the Ellis group of any minimal tame flow has Hausdorff tau-topology. To do this, we introduce new set-theoretic methods in topological dynamics which allow us to apply forcing and absoluteness arguments. As a consequence, we obtain a partial version of Glasner's structure theorem for general minimal tame flows. Joint work with Gianluca Basso.

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 80th Nankai Logic Colloquium--Andy Zucker Time: 9:00am, September 19, 2025(Beijing Time) Zoom Number: 347 405 3484 Passcode: 796087 Link: https://zoom.us/j/3474053484?pwd=bCM3G3C479kilUmP0RuWimJ47XxaLG.1&omn=95582665820

_____________________________________________________________________________________________________________________________________________________

Best regards,

Wei

This Week in Logic at CUNY

9/14/2025 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Sep 15, 2025 - - - -

Rutgers Logic Seminar

Monday 4:30pm, Rutgers University, Hill 705 (NOTE SPECIAL TIME)

Moti Gitik, Tel-Aviv University
On some PCF configurations

- - - - Tuesday, Sep 16, 2025 - - - -

- - - - Wednesday, Sep 17, 2025 - - - -

New York City Category Theory Seminar

Department of Computer Science
Department of Mathematics

The Graduate Center of The City University of New York

Room 6496
Speaker: Sam McCrosson, Montana State University.
Date and Time: Wednesday September 17, 2025, 7:00 - 8:30 PM. ZOOM TALK.
Title: Using Microsupports to Detect and Describe Constructible Sheaves.

Abstract: Microlocal sheaf theory has been gaining popularity recently for its applications to symplectic geometry. In this talk, we’ll explore a more topological application of this subject: how the notion of the microsupport of a sheaf can be used to tell if a sheaf is “constructible,” i.e. locally constant on strata, and if so, what the coarsest stratification is with this property.

Versions of this result can be found as far back as Kashiwara and Schapira’s 1990 book “Sheaves on Manifolds” (which pioneered the subject of microlocal sheaf theory). Today, all sorts of generalizations are possible using schemes, \infty-categories, and other fancy machinery. This talk will focus on a particularly simple case: using 1-category theory and sheaves of sets on topological spaces to illustrate the key ideas with concrete examples.

- - - - Thursday, Sep 18, 2025 - - - -

- - - - Friday, Sep 19, 2025 - - - -

Logic Workshop
CUNY Graduate Center
Friday, September 19, 2:00pm-3:30pm, Room 6417

James Walsh, New York University

A theory satisfying a strong version of Tennenbaum's theorem

Tennenbaum's theorem states that no non-standard model of PA is computable. Hence, no unsound extension of PA has computable models. Pakhomov recently showed that this consequence of Tennenbaum's theorem is fragile; it depends on the signature in which PA is presented. In particular, there is a theory T such that (i) T is definitionally equivalent to PA (this is a strong form of bi-interpretability) and (ii) every consistent r.e. extension of T has a computable model. Pakhomov's techniques yield analogous results for ZF and other canonical systems. He asked whether there is a consistent, r.e. theory T such that no theory which is definitionally equivalent to T has a computable model. We answer this question with an ad hoc construction. This is joint work with Patrick Lutz.

Next Week in Logic at CUNY:

- - - - Monday, Sep 22, 2025 - - - -

Rutgers Logic Seminar

Monday 3:30pm, Rutgers University, Hill 705

Cecelia Higgins, Rutgers
Measurable Brooks's Theorem for Directed Graphs

Logic and Metaphysics Workshop
Date: Monday, April 4/7, 2-4pm (NY time)
Room: Graduate Center Room
Fernando Cano-Jorge (Otago).
Title: The heresies project

Abstract: In the late 90’s, Richard Sylvan and Jack Copeland advanced the idea that computability is logic relative and that the Church-Turing thesis is false. Sylvan called this The Heresies Project and at its core is the idea that couching computability theory on a paraconsistent logic can take us beyond the classically computable. In the first part of this talk, I provide a brief introduction to paraconsistent computability theory, distinguishing non-revisionary approaches vs. Sylvan and Copeland’s more radical proposal. In the second part of this talk, I discuss what is required to pursue The Heresies Project. I will focus on Robinson arithmetic based on Sylvan’s preferred logic, DK, and its ability to both represent all recursive functions and prove Gödel’s first incompleteness theorem. I conclude that one of the keys to The Heresies Project, i.e. using an inconsistent metatheory, seems to clash with the arithmetic’s capacity to capture all recursive functions.

- - - - Tuesday, Sep 23, 2025 - - - -

- - - - Wednesday, Sep 24, 2025 - - - -

- - - - Thursday, Sep 25, 2025 - - - -

- - - - Friday, Sep 26, 2025 - - - -

MAMLS Fall Fest 2025
The 2025 Rutgers MAMLS meeting will take place on Sept. 26-28 at Rutgers University, in New Brunswick, NJ. Talks begin at 3:30 pm on Friday, 10:00 am on Saturday, and 9:30 am on Sunday, ending Sunday at 12:30. For details and to register, please visit the website. Some travel support is available: enquire with Prof. Filippo Calderoni.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

RIMS workshop on Set Theory 2025

Conference

09/09/2025

RIMS workshop on Set Theory 2025 - Recent Developments in Axiomatic Set Thoery From 16th to 19th Dec. 2025, at the Research Institute for Mathematical Sciences, Kyoto University This workshop will be held as a hybrid workshop at RIMS, Kyoto University, Japan & Online via Zoom. Invited Speakers David Chodounský (The Institute of Mathematics of the Czech Academy of Sciences) Tutorial Katsuya Eda (Waseda University) Boriša Kuzeljević (University of Novi Sad) Tadatoshi Miyamoto (Nanzan University) Registration The registration form is available at the link below. The deadline of contributed talks is on 31st Oct. 2025. Organizer Teruyuki Yorioka (Shizuoka University)

Link to more info

Tagged: David Chodounsky, Katsuya Eda, Boriša Kuzeljević, Tadatoshi Miyamoto

Wednesday seminar

Prague Set Theory Seminar

9/1/2025 1:54:14

Dear all, The seminar meets on Wednesday September 3rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. There will be no seminar next week September 10th (probably) as many people are away. The seminar should meet again on Wednesday September 17th for a talk of Luke Serafin (Cornell University). Program: Jesús Alberto Soria Rojas -- Q-points, selective ultrafilters and idempotents with an application to choiceless set theory We will study ultrafilters from the perspective of the algebra in the Čech-Stone compactification of the natural numbers, and idempotent elements therein. The first two results that we will present establish that, if p is a Q-point (resp. a selective ultrafilter) and F^p (resp. G^p) is the smallest family containing p and closed under iterated sums (resp. closed under Blass-Frolík sums and Rudin-Keisler images), then F^p (resp. G^p) contains no idempotent elements. The second of these results about a selective ultrafilter has the following interesting consequence: assuming a conjecture of Blass, in models of the form L(R)[p] where L(R) is a Solovay model (of ZF without choice) and p is a selective ultrafilter, there are no idempotent elements. In particular, the theory ZF plus the existence of a nonprincipal ultrafilter on the naturals does not imply the existence of idempotent ultrafilters, which answers a question of Di Nasso and Tachtsis (Proc. Amer. Math. Soc. 146, 397--411) that was also asked by Tachtsis (J. Symb. Log. 83, 557--571). This is joint work with David Fernández-Bretón and Jareb Navarro-Castillo. Best, David

This Week in Logic at CUNY

9/1/2025 22:00:00

Welcome back, everyone!

Jonas

This Week in Logic at CUNY:

- - - - Monday, Sep 1, 2025 - - - -

CUNY CLOSED

- - - - Tuesday, Sep 2, 2025 - - - -

- - - - Wednesday, Sep 03, 2025 - - - -

- - - - Thursday, Sep 04, 2025 - - - -

- - - - Friday, Sep 05, 2025 - - - -

Next Week in Logic at CUNY:

- - - - Monday, Sep 8, 2025 - - - -

Rutgers Logic Seminar
Monday 3:30pm, Rutgers University, Hill 705

Tom Benhamou, Rutgers
Cardinal Characteristics at Large Cardinals

- - - - Tuesday, Sep 9, 2025 - - - -

- - - - Wednesday, Sep 10, 2025 - - - -

- - - - Thursday, Sep 11, 2025 - - - -

- - - - Friday, Sep 12, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, September 12, 11:00am NY time

Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)

Rahman Mohammadpour, Institute of Mathematics of Polish Academy of Sciences
Specializing Triples

I will talk about weak embeddability and the universality number of the class of Aronszajn trees, with a focus on the role of specializing triples.

The notion of a specializing triple was introduced by Džamonja and Shelah in their strong negative solution to an old problem on the existence of a universal (with respect to weak embeddability) wide Aronszajn tree under Martin's axiom. Their proof has two stages: first, they reprove a theorem of Todorčević showing that under $M A ω 1$ there is no universal Aronszajn tree, and then they show that every wide Aronszajn tree weakly embeds into an Aronszajn tree. The second stage involves a rather complicated ccc forcing. However, already in the first stage, they introduce a new technique: the notion of a specializing triple, and prove that for each Aronszajn tree $T$ , there is a ccc forcing adding another Aronszajn tree $T *$ together with a specializing function on $T * \otimes T$ such that $(T *, T, c)$ is a specializing triple. In particular, this shows that $T *$ does not weakly embed into $T$ .

I will explain how a slight but careful modification of this definition makes it possible to accommodate wide trees directly, yielding a more streamlined proof of Džamonja and Shelah’s result. More precisely, for every $κ$ -wide Aronszajn tree $T$ , there is a ccc forcing adding an Aronszajn tree $T *$ and a function $c$ such that $(T *, T, c)$ is what I call a left specializing triple. From this, one quickly recovers Džamonja-Shelah’s theorem: under Martin’s axiom, every class of trees of height $ω 1$ and size less than the continuum but with no cofinal branches either is not universal for Aronszajn trees, or has universality number equal to the continuum.

Finally, I will indicate how the modified definition can also be used to show that this consequence of Martin’s axiom is consistent with the existence of a nonspecial Aronszajn tree.

- - - - 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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This Week in Logic at CUNY

9/7/2025 22:25:00

This Week in Logic at CUNY:

- - - - Monday, Sep 8, 2025 - - - -

Rutgers Logic Seminar

Monday 4:30pm, Rutgers University, Hill 705 (NOTE SPECIAL TIME)

Tom Benhamou, Rutgers
Cardinal Characteristics at Large Cardinals

- - - - Tuesday, Sep 9, 2025 - - - -

- - - - Wednesday, Sep 10, 2025 - - - -

- - - - Thursday, Sep 11, 2025 - - - -

- - - - Friday, Sep 12, 2025 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, September 12, 11:00am NY time

Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)

Rahman Mohammadpour, Institute of Mathematics of Polish Academy of Sciences
Specializing Triples

I will talk about weak embeddability and the universality number of the class of Aronszajn trees, with a focus on the role of specializing triples.

The notion of a specializing triple was introduced by Džamonja and Shelah in their strong negative solution to an old problem on the existence of a universal (with respect to weak embeddability) wide Aronszajn tree under Martin's axiom. Their proof has two stages: first, they reprove a theorem of Todorčević showing that under there is no universal Aronszajn tree, and then they show that every wide Aronszajn tree weakly embeds into an Aronszajn tree. The second stage involves a rather complicated ccc forcing. However, already in the first stage, they introduce a new technique: the notion of a specializing triple, and prove that for each Aronszajn tree , there is a ccc forcing adding another Aronszajn tree together with a specializing function on such that is a specializing triple. In particular, this shows that does not weakly embed into .

I will explain how a slight but careful modification of this definition makes it possible to accommodate wide trees directly, yielding a more streamlined proof of Džamonja and Shelah’s result. More precisely, for every -wide Aronszajn tree , there is a ccc forcing adding an Aronszajn tree and a function such that is what I call a left specializing triple. From this, one quickly recovers Džamonja-Shelah’s theorem: under Martin’s axiom, every class of trees of height and size less than the continuum but with no cofinal branches either is not universal for Aronszajn trees, or has universality number equal to the continuum.

Finally, I will indicate how the modified definition can also be used to show that this consequence of Martin’s axiom is consistent with the existence of a nonspecial Aronszajn tree.

Logic Workshop
CUNY Graduate Center
Friday, September 12, 2:00pm-3:30pm, Room 6417

Gunter Fuchs, CUNY
Strong reflection, saturation and diagonal reflection. A study of a triangle relationship.

There is a natural way to formulate fragments of Todorcevic’s strong reflection principle (SRP) which are associated to forcing classes more restrictive than the class of all stationary set preserving forcing notions. The fragment associated to the subcomplete forcings (SC-SRP), while retaining many crucial consequences of SRP, is compatible with CH, and even Jensen's Diamond Principle. In particular, the saturation of the nonstationary ideal, a celebrated consequence of SRP, does not follow from its subcomplete fragment. In fact, adding CH to SC-SRP results in a principle which outright contradicts the saturation of the nonstationary ideal. A specific form of diagonal reflection of stationary sets of ordinal was used by Paul Larson to separate SRP from Martin's Maximum: that form of diagonal reflection follows from MM, but not from SRP. The surprising initial observation is that it does follow from SC-SRP + CH. The key reason for this is that SC-SRP + CH implies the nonsaturation of the nonstationary ideal. Thus, an apparent weakness of SC-SRP + CH turns out to be a strength in this context.

I will introduce the concepts involved and present some further results along these lines. The picture that emerges is that in the context of SC-SRP, saturation and diagonal reflection work against each other.

This is joint work with Hiroshi Sakai.

Next Week in Logic at CUNY:

- - - - Monday, Sep 15, 2025 - - - -

Rutgers Logic Seminar

Monday 4:30pm, Rutgers University, Hill 705 (NOTE SPECIAL TIME)

Moti Gitik, Tel-Aviv University
On some PCF configurations

- - - - Tuesday, Sep 16, 2025 - - - -

- - - - Wednesday, Sep 17, 2025 - - - -

New York City Category Theory Seminar

Department of Computer Science
Department of Mathematics

The Graduate Center of The City University of New York

Room 6496
Speaker: Sam McCrosson, Montana State University.
Date and Time: Wednesday September 17, 2025, 7:00 - 8:30 PM. ZOOM TALK.
Title: Using Microsupports to Detect and Describe Constructible Sheaves.

Abstract: Microlocal sheaf theory has been gaining popularity recently for its applications to symplectic geometry. In this talk, we’ll explore a more topological application of this subject: how the notion of the microsupport of a sheaf can be used to tell if a sheaf is “constructible,” i.e. locally constant on strata, and if so, what the coarsest stratification is with this property.

Versions of this result can be found as far back as Kashiwara and Schapira’s 1990 book “Sheaves on Manifolds” (which pioneered the subject of microlocal sheaf theory). Today, all sorts of generalizations are possible using schemes, \infty-categories, and other fancy machinery. This talk will focus on a particularly simple case: using 1-category theory and sheaves of sets on topological spaces to illustrate the key ideas with concrete examples.

- - - - Thursday, Sep 18, 2025 - - - -

- - - - Friday, Sep 19, 2025 - - - -

Logic Workshop
CUNY Graduate Center
Friday, September 19, 2:00pm-3:30pm, Room 6417

James Walsh, New York University

- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT:

Mid-Atlantic Mathematical Logic Seminar
Fall Fest 2025
September 26-28, New Brunswick

website

Confirmed speakers:

Tom Benhamou (Rutgers)
Will Boney (Texas State)
Yutong Duan (UIC)
James Freitag (UIC)
Vika Gitman (CUNY)
Ted Slaman (UC Berkeley)
Henry Towsner (U Penn)
Anush Tserunyan (McGill)
James Walsh (NYU)

- - - - 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

9/12/2025 4:19:06

Dear all, The seminar meets on Wednesday September 17th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Luke Serafin -- Tukey Types of Ultrafilters Over Omega_1 Justin Moore, Tom Benhamou, and the author undertook a study of the Tukey-types of uniform ultrafilters over omega_1, and the main results from the perspective of our original intentions were that it is consistent for all uniform ultrafilters over omega_1 to be Tukey-top, and consistent relative to large cardinals that there is a uniform ultrafilter over omega_1 which is not Tukey-top. I shall briefly review these results, but my main focus is work regarding Todorcevic's filter U(T) for T a coherent Aronszajn tree on omega_1. Remarkably, this simply-definable filter is an ultrafilter under mild forcing axioms. We shall see that ccc forcing constructions allow ultrafilters of this form to extend the filter generated in the extension by any nonprincipal filter in V. This ultrafilter is also Tukey-top and Rudin-Keisler minimal under PFA. Best, David

Conference

01/12/2025

We would like to announce: TITLE: Young Topology and Set Theory Meeting. DATES: January 29-30, 2025. WEBPAGE: https://topology2025-catania.blogspot.com/ DESCRIPTION: Our conference aims to bring together young researchers in topology and set theory in order to discuss the latest advances and main open problems involving those fields and their interaction. The conference will take place online and in person at the University of Catania, Italy and at the Universidad Autonoma Metropolitana in Mexico City. The speakers are PhD students and junior post-docs investigating a diverse range of topics within set theory and topology: from topological cardinal invariants to infinitary combinatorics, from descriptive set theory to selection principles, from topological data analysis to models without choice.

Link to more info

Jörg Brendle's 60th birthday conference, Kobe, September 1-5, 2025

Conference

01/08/2025

The conference in honor of Jörg Brendle, on the occasion of his 60th birthday, will be held entirely in person for four or five days in the week of September 1st to 5th, 2025, at Kobe University. This conference will be succeeded in the following week by the 18th Asian Logic Conference in Kyoto, Japan. More information (including registration) will be open around April in 2025. The organizers are: Hiroshi Sakai (University of Tokyo) Diego A. Mejía (Kobe University) Hiroaki Minami (Aichi Gakuin University) Teruyuki Yorioka (Shizuoka University)

Link to more info

58th Nankai Logic Colloquium

Nankai Logic Colloquium

11/4/2024 4:02:00

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon. Our speaker this week will be Haosui Duanmu from the Harbin Institute of Technology. This talk will take place this Friday, November 8th, from 4pm to 5pm (UTC+8, Beijing time).

Title: Nonstandard Decision Theory

Abstract: Nonstandard analysis, a powerful machinery derived from mathematical logic, has had many applications in probability theory as well as stochastic processes. Nonstandard analysis allows construction of a single object—a hyperfinite probability space—which satisfies all the first order logical properties of a finite probability space, but which can be simultaneously viewed as a measure-theoretical probability space via the Loeb construction. As a consequence, the hyperfinite/measure duality has proven to be particularly in porting discrete results into their continuous settings.

The connection between frequentist and Bayesian optimality in statistical decision theory is a longstanding open problem. For statistical decision problems with a finite parameter space, it is well known that a decision procedure is extended admissible (frequentist optimal) if and only if it is Bayes. Such connection becomes fragile for decision problems with an infinite parameter space and one must relax the notion of Bayes optimality to regain such equivalence between extended admissibility and Bayes optimality. Various attempts have been made in the literature but they are subject to technical conditions which often rule our semi-parametric and nonparametric problems. By using nonstandard analysis, we develop a novel notion of nonstandard Bayes optimality (Bayes with infinitesimal excess risk). We show that, without any technical condition, a decision procedure is extended admissible if and only if it is nonstandard Bayes. We conclude by showing that several existing standard results in the literature can be derived from our main result.

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 58th Nankai Logic Colloquium-- Haosui Duanmu Time: 16:00pm, Nov. 8, 2024(Beijing Time) Zoom Number: 436 658 8683 Passcode: 477893 Link: https://frontai-hk.zoom.us/j/4366588683?pwd=ob0TsLuLeIl0JT7403RaqvFKgOnuRf.1&omn=82954404806

___________________________________________________________________________________________________________________________________________________________________

Best regards,

Wei

Logic Seminar 6 Nov 2024 17:00 hrs by Michael Takaaki Leong at NUS

NUS Logic Seminar

11/4/2024 3:29:36

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 06.11.2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Michael Takaaki Leong Title: A weakening of a Suslin tree with variants of Martin's Axiom Abstract: A weakening of a Suslin tree, known as a Suslin lattice, was introduced by Dilworth, Odell, and Sari in 2007, and subsequently investigated by Raghavan and Yorioka in 2012. In this talk, we will show that the compatibility of a Suslin lattice with Martin's Axiom and its variants mirrors that of a Suslin tree by showing that a fragment of Martin's Axiom suffices to imply the non-existence of a Suslin lattice. We will also discuss the possible consistency of a Suslin lattice with the P-ideal Dichotomy. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

11/3/2024 22:36:00

This Week in Logic at CUNY:

- - - - Monday, Nov 4, 2024 - - - -

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

Elena Ficara (Paderborn)
Title: Logic and discrimination

Abstract: My talk is about the connection between logic and discrimination, with special focus on Plumwood’s ideas in her groundbreaking article ‘The Politics of Reason. Towards a Feminist Logic’ (1993). Although Plumwood’s paper is not focused on the notion of discrimination, what she writes is useful for illuminating some basic mechanisms of thought that are at the basis of discriminatory practices. After an introductory section about the concepts of logic and discrimination at the basis of my analysis, I present Plumwood’s ideas in 1993 with a special focus on their relevance for understanding the nature of discrimination. More specifically, I use examples of discriminatory practices that make the connection between logical operations and oppression envisaged by Plumwood clear. I focus especially on two questions: Can logic produce discrimination? Can logic contribute to the fight against discrimination? If so, how?

- - - - Tuesday, Nov 5, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, November 5, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Piotr Gruza, University of Warsaw

- - - - Wednesday, Nov 6, 2024 - - - -

Philosophy Colloquium
Wednesday Nov 6, 4:15 P.M. to 6:15 P.M, CUNY Graduate Center Room 9206/9207

Alan Hájek

Professor of Philosophy, Australian National University
“A Chancy Theory of Counterfactuals”

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: David Jaz Myers, NYU Abu Dhabi.

Date and Time: Wednesday November 6, 2024, SPECIAL TIME: 2:00 PM NYC TIME (contact N Yanofsky noson@sci.brooklyn.cuny.edu for zoom link)

Title: Contextads: Para and Kleisli constructions as wreath products.

Abstract: Given a comonad D on a category C, we can produce a double category whose tight maps are those of C and whose loose maps are Kleisli maps for D --- this is the Kleisli double category kl(D). Given a monoidal right action & : C x M --> C, we can produce a double category Para(&) whose tight maps are those of C and whose loose maps A -|-> B are pairs (P, f : A & P --> B) of a parameter space P in M and a parameterised map f.

In this talk, we'll see both these as special cases of a general construction: the Ctx construction which takes a *contextad* on a (double) category and produces a new double category. We'll see that this construction is "just" the wreath product of pseudo-monads in Span(Cat). We'll then exploit this observation to find 2-algebraic structure on the Ctx constructions of suitably structured contextads; vastly generalizing the old observation that a colax monoidal comonad has a monoidal Kleisli category.

This is joint work with Matteo Capucci.

- - - - Thursday, Nov 7, 2024 - - - -

Rutgers Logic Seminar
Thursday November 7, 2pm, Rutgers University, Hill Center, Hill 423

NOTE SPECIAL DAY/TIME/LOCATION

Assaf Shani, Concordia University
Generic dichotomies for Borel homomorphisms for the finite Friedman-Stanley jumps

- - - - Friday, Nov 8, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, November 8, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Geoff Galgon,
Distributivity and Base trees for

For a regular uncountable cardinal, we show that distributivity and base trees for of intermediate height in the cardinal interval exist in certain models. We also show that base trees of height can exist as well as base trees of various heights depending on the spectrum of cardinalities of towers in . These constructions answer questions of V. Fischer, M. Koelbing, and W. Wohofsky in certain models.

Logic Workshop
CUNY Graduate Center
Friday, November 8, 2:00pm-3:30pm, Room 4419

Artem Chernikov University of Maryland

Next Week in Logic at CUNY:

- - - - Monday, Nov 11, 2024 - - - -

Rutgers Logic Seminar
Monday November 11, 3:30pm, Rutgers University, Hill Center, Hill 705

Frank Wagner, Ohio State

Logic and Metaphysics Workshop
Date: Monday, November 11, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Friederike Moltmann (CNRS).
Title: On the ontology and semantics of absence

Abstract: This talk proposes a new semantic analysis of verbs of absence such as ‘lack’ and ‘be missing’. The semantics is based on the notion of a conceptual whole and its (conceptual) parts, which generates both variable embodiments (of the whole and its structural parts) and modal objects of the sort of a ‘lack’. It involves an extension of truthmaker semantics (applied to modal objects) where truthmakers (satisfiers) now include parts of wholes. The talk rehabilitates entities of the sort of ‘lacks’ often subject to ridicule, most notoriously by Chomsky.

- - - - Tuesday, Nov 12, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, November 12, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Piotr Gruza, University of Warsaw

- - - - Wednesday, Nov 13, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker:    Emilio Minichiello, CUNY CityTech.
Date and Time:     Wednesday November 13, 2024, 7:00 - 8:30 PM.IN-PERSON TALK. CUNY Graduate Center Room 6417
Title:     Decision Problems on Graphs with Sheaves.

Abstract: This semester I don’t feel like talking about my research. Instead I’ll talk about what I’ve learned from reading the paper Compositional Algorithms on Compositional Data: Deciding Sheaves on Presheaves by Althaus, Bumpus, Fairbanks and Rosiak. This paper is about how we can use sheaf theory to break apart a computational problem, solve it on small pieces, and then glue the solutions together to get a global solution to the computational problem. I’ll go through the main ideas of this paper, using the category of simple graphs with monomorphisms as a main example to showcase their results.

- - - - Thursday, Nov 14, 2024 - - - -

- - - - Friday, Nov 15, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, November 15, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Philipp Schlicht Kurt Gödel Research Center

Logic Workshop
CUNY Graduate Center
Friday, November 15, 2:00pm-3:30pm, Room 4419

Russell Miller, CUNY
Computable reductions on groups and fields

Hjorth and Thomas established that the complexity of the isomorphism problem for torsion-free abelian groups of finite rank grows dramatically higher as the rank increases: for each $r$ , there is no Borel function $F$ that maps each rank- $(r + 1)$ group $G$ to a rank- $r$ group $F (G)$ in such a way that $G 0 ≅ G 1 ⟺ F (G 0) ≅ F (G 1)$ . We say that there is no Borel reduction from isomorphism on $TFAb r + 1$ to isomorphism on $TFAb r$ . (From lower to higher rank, in contrast, such a reduction is readily seen.) Fields of transcendence degree $r$ over $Q$ have very similar computability properties to groups in $TFAb r$ . This being so, we extend their investigations to include the isomorphism relations on the classes $FD r$ of such fields. We show that there do exist reductions (not merely Borel, but actually computable, and moreover functorial) from each $TFAb r$ to the corresponding $FD r$ , and also from each $FD r$ to $FD r + 1$ (which proves more challenging than it was for the groups!). It remains open whether a theorem analogous to that of Hjorth-Thomas holds for the fields, but we use the notion of countable reductions to show that the fundamental obstacle to a reduction from $TFAb r + 1$ to $TFAb r$ is the uncountability of these spaces. This is joint work with Meng-Che 'Turbo' Ho and Julia Knight.

- - - - 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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Set Theory in the United Kingdom, Cambridge, November 18, 2024

Conference

11/2/2024 18:28:02

STUK 14 is the fourteenth installment of the series and will take place at Churchill College, Cambridge on Monday, 18 November 2024. The meeting will also be broadcast via zoom, please get in touch for joining info. Invited speakers include: Zachiri McKenzie (Chester) End extensions of models of subsystems of ZF Tristan van der Vlugt (Vienna) The horizontal direction & other differences between the classical and higher Cichoń diagram Allison Wang (Pittsburgh PA) Complexity of codes for Ramsey positive sets Talks will be in the Bevin Room: when entering the College through the main gate, go straight ahead along the Concourse to the end, turn left, and leave the building through a glass door, use the covered walkpath to the opposite building; the Bevin Room is one of the seminar rooms accessible from the foyer of the building.

Link to more info

Summer School on Topology, dynamics, and logic in interaction, in Cetraro, Italy, September 1-5, 2025

Conference

11/2/2024 17:28:02

Registrations are open for a Summer School in Cetraro, Italy, September 1-5, 2025, on "Topology, dynamics, and logic in interaction" Some funding is available to support the attendance of early-career researchers The full list of minicourses and lecturers can be found at https://sites.google.com/unifi.it/cime/c-i-m-e-courses/c-i-m-e-courses-2025/topology-dynamics-and-logic-in-interaction

Link to more info

Set theory and topology seminar 05.11.2024 Paweł Krupski

Wrocław Set Theory Seminar

11/2/2024 16:28:02

I am happy to announce that at the seminar in set theory and topology on 2024-11-05 Tuesday 17:15 in MI, 605 the lecture:

An update on hyperspaces of knots.

will be presented by

Paweł Krupski

Abstract: New properties of the hyperspaces of simple closed curves in the plane or in the 3-space will be presented. In particular, the hyperspace of polygonal knots is a sigma-compact, strongly countable-dimensional ANR which is an infinite-dimensional Cantor manifold. The hyperspace of tame knots is an absolute Borel, strongly infinite-dimensional Cantor manifold. Joint work with Krzysztof Omiljanowski.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You,
on behalf of all the organizers,
PBN

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

***

Our webpages:
https://prac.im.pwr.edu.pl/~settheory
https://settheory.pwr.edu.pl/ (legacy page)
http://www.math.uni.wroc.pl/seminarium/topologia

Wednesday seminar and other events

Prague Set Theory Seminar

10/31/2024 7:23:55

Dear all, There will be no seminar next week Wednesday November 6th due to the open house days in the Institute. However, there will be multiple events during the week of November 11.--15. Monday November 11, 16:30 -- Colloquium of the MLTCS department Wednesday November 13, 11:00 -- Seminar on reckoning Friday November 15, whole day -- Set theory workshop with University of Vienna Some more info: The colloquium/joint logic seminar of the MLTSC department will take place on Monday November 11th at 16:30, blue lecture hall, Institute of Mathematics CAS, Zitna 25. The seminar will start at 16:15 with coffee and cakes, after the talk we will go for drinks/dinner/.. Program: Pedro Marun -- TBA The seminar will take place as usual on Wednesday November 13th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Hannes Jakob (a student of Heike Mildenberger visiting Prague) -- TBA Radek Honzik (FF UK) and Vera Fisher will organize a small workshop. Forwarding information from Radek: Vera Fischer and myself will organize a small workshop which will take place on Friday 15.11.2024 at the Department of Logic of the Charles University, Celetna 20, Praha 1. We will have 5 people from Vienna (Vera, Corey, Monroe, Julia, Valentin). We would be happy if you could take part. Would you like to give a talk lasting either 30 or 50 mins (at your preference)? We have a room reserved which might not have a projector, so it would be better if you could do the traditional BB talk. Please let me know, we will prepare a schedule and Vera will also set up a website to make it official. If any of your students or colleagues at the Institute would like to attend as well, they are welcome, please let them know. Ask them to write an email to me to confirm so that I can send any updates to them directly. Best, David

This Week in Logic at CUNY

10/27/2024 22:30:00

This Week in Logic at CUNY:

- - - - Monday, Oct 28, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Monday, October 28, 2pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Sun Mengzhou, National University of Singapore
The Kaufmann–Clote question on end extensions of models of arithmetic and the weak regularity principle

We investigate the end extendibility of models of arithmetic with restricted elementarity. By utilizing the restricted ultrapower construction in the second-order context, for each and any countable model of , we construct a proper -elementary end extension satisfying , which answers a question by Clote positively. We also give a characterization of countable models of in terms of their end extendibility similar to the case of . Along the proof, we will introduce a new type of regularity principles in arithmetic called the weak regularity principle, which serves as a bridge between the model's end extendibility and the amount of induction or collection it satisfies.
The talk is based on this paper from arxiv:2409.03527.

Rutgers Logic Seminar
Monday October 28, 3:30pm, Rutgers University, Hill Center, Hill 705

Danielle Ullrich, Maryland

Logic and Metaphysics Workshop
Date: Monday, October 28, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Panelists: Hartry Field (NYU), Mel Fitting (CUNY), Noah Greenstein (Independent Scholar), Graham Priest (CUNY), and Achille Varzi (Columbia)

Topic: The present and future of logic and metaphysics

The Logic and Metaphysics Workshop will meet on October 28th from 4:15-6:15 in-person at the Graduate Center (Room 4419) to celebrate its 10th Anniversary. For this special occasion, there will be a panel discussing (inter alia) currents trends in, and the future of, Logic and Metaphysics.

- - - - Tuesday, Oct 29, 2024 - - - -

- - - - Wednesday, Oct 30, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Date and Time: Wednesday October 30, 2024, 2:00PM NYC Time. NOTE SPECIAL TIME. ZOOM TALK (contact N Yanofsky noson@sci.brooklyn.cuny.edu for zoom link)
Speaker: Bruno Gavranović, Symbolica AI.
Title: Categorical Deep Learning: An Algebraic Theory of Architectures.Date and Time:

- - - - Thursday, Oct 31, 2024 - - - -

6th Saul Kripke Lecture

The Saul Kripke Center

Date: October 31st, 2024, from 4:00 to 6:30 pm,

Room: CUNY Graduate Center Room C198

Kit Fine, Silver Professor and University Professor of Philosophy and Mathematics at NYU

Title: The Myth of the Ungiven

Abstract: The notion of a borderline case has been thought to be central to our understanding of vagueness. I shall argue that there is no intelligible notion that can play this role and that an alternative framework for understanding vagueness needs to be found.

- - - - Friday, Nov 1, 2024 - - - -

MAMLS (The Mid-Atlantic Mathematical Logic Meeting)

Rutgers University

November 1 - 3, 2004

November 1, the first day of the three-day Rutgers MAMLS Fall Fest: Talks this afternoon are to be given by Justin Moore (3:00 pm) and Valentina Harizanov (4:30 pm) in Rutgers University’s Murray Hall in downtown New Brunswick, NJ. Those planning to attend should please register in advance here, where further information is available.

Next Week in Logic at CUNY:

- - - - Monday, Nov 4, 2024 - - - -

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

Elena Ficara (Paderborn)
Title: Logic and discrimination

Abstract: My talk is about the connection between logic and discrimination, with special focus on Plumwood’s ideas in her groundbreaking article ‘The Politics of Reason. Towards a Feminist Logic’ (1993). Although Plumwood’s paper is not focused on the notion of discrimination, what she writes is useful for illuminating some basic mechanisms of thought that are at the basis of discriminatory practices. After an introductory section about the concepts of logic and discrimination at the basis of my analysis, I present Plumwood’s ideas in 1993 with a special focus on their relevance for understanding the nature of discrimination. More specifically, I use examples of discriminatory practices that make the connection between logical operations and oppression envisaged by Plumwood clear. I focus especially on two questions: Can logic produce discrimination? Can logic contribute to the fight against discrimination? If so, how?

- - - - Tuesday, Nov 5, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Tuesday, November 5, 1pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Piotr Gruza, University of Warsaw

- - - - Wednesday, Nov 6, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York

Speaker: David Jaz Myers, NYU Abu Dhabi.

Date and Time: Wednesday November 6, 2024, ZOOM TALK. TIME TBA (contact N Yanofsky noson@sci.brooklyn.cuny.edu for zoom link)

Title: Contextads: Para and Kleisli constructions as wreath products.

Abstract: Given a comonad D on a category C, we can produce a double category whose tight maps are those of C and whose loose maps are Kleisli maps for D --- this is the Kleisli double category kl(D). Given a monoidal right action & : C x M --> C, we can produce a double category Para(&) whose tight maps are those of C and whose loose maps A -|-> B are pairs (P, f : A & P --> B) of a parameter space P in M and a parameterised map f.

In this talk, we'll see both these as special cases of a general construction: the Ctx construction which takes a *contextad* on a (double) category and produces a new double category. We'll see that this construction is "just" the wreath product of pseudo-monads in Span(Cat). We'll then exploit this observation to find 2-algebraic structure on the Ctx constructions of suitably structured contextads; vastly generalizing the old observation that a colax monoidal comonad has a monoidal Kleisli category.

This is joint work with Matteo Capucci.

- - - - Thursday, Nov 7, 2024 - - - -

Rutgers Logic Seminar
Thursday November 7, 2pm, Rutgers University, Hill Center, Hill 423

NOTE SPECIAL DAY/TIME/LOCATION

Assaf Shani, Concordia University
Generic dichotomies for Borel homomorphisms for the finite Friedman-Stanley jumps

10/20/2024 22:25:00

This Week in Logic at CUNY:

- - - - Monday, Oct 21, 2024 - - - -

Rutgers Logic Seminar
Monday October 21, 3:30pm, Rutgers University, Hill Center, Hill 705

Jason Block, CUNY
Elementarity of Subgroups and Complexity of Theories for Profinite Groups

Logic and Metaphysics Workshop
Date: Monday, October 21, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Thomas M. Ferguson (Rensselaer).
Title: Qua, per se, and other topic-transformative operators

Abstract: Recent work challenging principles of topic transparency in topic-sensitive logics has relied on providing accounts of connectives that are topic-transformative, that is, which non-trivially influence the overall topic assigned to a complex. This leads naturally to the question of what operators in natural language might also act as topic-transformative functions. This talk reviews work in progress studying “qua”, “per se”, and other topic-transformative operators. After discussing ways to analyze these operators, we will emphasize how such analyses are likely to assist in a parallel project of updating Richard Sylvan’s work on relevant containment logic.

Note: This is joint work with Pietro Vigiani (Pisa) and Jitka Kadlečková (Rensselaer).

- - - - Tuesday, Oct 22, 2024 - - - -

- - - - Wednesday, Oct 23, 2024 - - - -

- - - - Thursday, Oct 24, 2024 - - - -

- - - - Friday, Oct 25, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 25, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Stefan Geschke University of Hamburg

More Borel chromatic numbers

Borel chromatic numbers of definable graphs on Polish spaces have been studied for 25 years, starting with the seminal paper by Kechris, Solecky and Todorcevic. I will talk about some recent results about the consistent separation of uncountable Borel chromatic numbers of some particular graphs and about the Borel chromatic number of graphs related to Turing reducibility.

Logic Workshop
CUNY Graduate Center
Friday October 25, 2:00pm-3:30pm, Room 4419

Hans Schoutens, CUNY
Computing away negation using ancients: from existential to Diophantine sentences

Last semester, I discussed geometric methods for decidability over a complete discrete valuation ring (DVR) in equal characteristic, suggesting that these methods could be applied effectively. In this talk, I aim to clarify the computability issues surrounding this topic while at the same time shifting focus to the case of mixed characteristic. Whereas quantifier elimination (QE) results are established for p-adic numbers, the general landscape remains less explored. I will demonstrate that for any existential sentence over a computable ring, we can effectively construct a positive existential (or Diophantine) sentence which is logically equivalent to the original in every excellent Henselian DVR containing the ring. This construction hinges on Resolution of Singularities, which is feasible in characteristic zero.

Furthermore, I will utilize ultraproducts, specifically the protoproduct variant, to show how Diophantine statements over a DVR can be reduced to those over a residue ring. Since the residue ring is Artinian—and in the case of p-adics, even finite—the associated problems become significantly more manageable. However, it is important to note that this approach does not yet yield a general QE result, as it applies only to sentences, not formulas. The challenge lies in the dependence of certain effective bounds on parameters. I will provide insights into how to derive a bound based on a refined notion of complexity within the equational system—beyond simply considering its degree—using ultraproducts. Additionally, I will address a request from the audience in my last talk by demonstrating that this bound is indeed effective.

And somehow it will also require some delving into the theory of Witt vectors and ancient elements, as I will explain.

Next Week in Logic at CUNY:

- - - - Monday, Oct 28, 2024 - - - -

MOPA (Models of Peano Arithmetic)

Date: Monday, October 28, 2pm (NY time), CUNY Graduate Center

Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Sun Mengzhou, National University of Singapore
The Kaufmann–Clote question on end extensions of models of arithmetic and the weak regularity principle

We investigate the end extendibility of models of arithmetic with restricted elementarity. By utilizing the restricted ultrapower construction in the second-order context, for each $n \in N$ and any countable model of $B Σ n + 2$ , we construct a proper $Σ n + 2$ -elementary end extension satisfying $B Σ n + 1$ , which answers a question by Clote positively. We also give a characterization of countable models of $I Σ n + 2$ in terms of their end extendibility similar to the case of $B Σ n + 2$ . Along the proof, we will introduce a new type of regularity principles in arithmetic called the weak regularity principle, which serves as a bridge between the model's end extendibility and the amount of induction or collection it satisfies.
The talk is based on this paper from arxiv:2409.03527.

Rutgers Logic Seminar
Monday October 28, 3:30pm, Rutgers University, Hill Center, Hill 705

Danielle Ullrich, Maryland

Logic and Metaphysics Workshop
Date: Monday, October 28, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Panelists: Hartry Field (NYU), Mel Fitting (CUNY), Noah Greenstein (Independent Scholar), Graham Priest (CUNY), and Achille Varzi (Columbia)

Topic: The present and future of logic and metaphysics

The Logic and Metaphysics Workshop will meet on October 28th from 4:15-6:15 in-person at the Graduate Center (Room 4419) to celebrate its 10th Anniversary. For this special occasion, there will be a panel discussing (inter alia) currents trends in, and the future of, Logic and Metaphysics.

- - - - Tuesday, Oct 29, 2024 - - - -

- - - - Wednesday, Oct 30, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Date and Time: Wednesday October 30, 2024, 2:00PM NYC Time. NOTE SPECIAL TIME. ZOOM TALK (contact N Yanofsky noson@sci.brooklyn.cuny.edu for zoom link)
Speaker: Bruno Gavranović, Symbolica AI.
Title: Categorical Deep Learning: An Algebraic Theory of Architectures.Date and Time:

- - - - Thursday, Oct 31, 2024 - - - -

- - - - Friday, Nov 1, 2024 - - - -

MAMLS (The Mid-Atlantic Mathematical Logic Meeting)

Rutgers University

November 1 - 3, 2004

November 1, the first day of the three-day Rutgers MAMLS Fall Fest: Talks this afternoon are to be given by Justin Moore (3:00 pm) and Valentina Harizanov (4:30 pm) in Rutgers University’s Murray Hall in downtown New Brunswick, NJ. Those planning to attend should please register in advance here, where further information is available.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Set theory and topology seminar 22.10.2024 Dominik Bargieła

Wrocław Set Theory Seminar

10/17/2024 15:23:49

I am happy to announce that at the seminar in set theory and topology (on Tuesday 22.10.2024 at 17:15 in room 60? (Mathematical Institute of Wrocław University) the lecture:

"Topological Stäckel Hypothesis"

will be presented by

Dominik Bargieła

Abstract:

In this talk I will try to introduce new notion of compactness called Stäckel compactness and compare it against other well-known kinds of compactness (with special emphasis on countable compactness). Moreover I will present and discuss the main problem whether Stäckel compactness coincides with countable compactness.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You

Szymon Żeberski

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

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

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

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

Logic Seminar at NUS on 23.10.2024 at 17:00 hrs by Ellen Hammatt

NUS Logic Seminar

10/17/2024 5:17:05

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 23 October 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Ellen Hammatt Title: Arriving on time: punctuality in structures, isomorphisms and 1-decidability In this talk we investigate what happens when we take concepts from computable structure theory and forbid the use of unbounded search. In other words, we discuss the primitive recursive content of structure theory. The central definition is that of punctual structures, introduced by Kalimullin, Melnikov and Ng in 2017. We investigate various concepts from computable structure theory in the primitive recursive case. A common theme is that new techniques are required in the primitive recursive case. In particular we will focus on topics such as finite punctual dimension, punctual 1-decidability and the punctual degrees. Where the punctual degrees is a degree structure within punctual presentations of a fixed structure which is induced by primitive recursive isomorphisms. I will present various results from my PhD thesis as well as pose some open questions in the area. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

57th Nankai Logic Colloquium

Nankai Logic Colloquium

10/16/2024 1:18:20

Hello everyone,

Welcome back to our weekly Nankai Logic Colloquium! The first colloquium of this semester will be held in an irregular time which is going to be in the afternoon next Wednesday (it usually holds every Friday).

Our speaker this time will be Natasha Dobrinen from the University of Notre Dame. This talk is going to take place next Wednesday, October 23rd, from 4pm to 5pm (UTC+8, Beijing time).

Title: Forcing and Ramsey theorems on trees

Abstract: The Halpern Läuchli Theorem is a Ramsey theorem for colorings of products of finitely many trees. It was found as a key step in Halpern and Lévy's proof that BPI is strictly weaker than the Axiom of Choice, over Zermelo-Fraenkel set theory. Harrington gave a proof of the Halpern Läuchli Theorem using forcing as a means for unbounded search for a finite object, rather than via a generic extension and absoluteness. This talk will focus on extensions of this theorem and Harrington's method to a genre of tree Ramsey theorems. Such theorems are at the heart of infinite structural Ramsey theory such as big Ramsey degrees, infinite-dimensional Ramsey theory on Fraïssé structures, uncountable structures, and computability-theoretic bounds.

______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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

Title: The 57th Nankai Logic Colloquium-- Natasha Dobrinen

Time: 16:00pm, Oct. 23, 2024(Beijing Time)

Zoom Number: 436 658 8683

Passcode: 477893

Link: https://frontai-hk.zoom.us/j/4366588683?pwd=ob0TsLuLeIl0JT7403RaqvFKgOnuRf.1&omn=83230616560

___________________________________________________________________________________________________________________________________________________________________

Best regards,

Wei

This Week in Logic at CUNY

10/13/2024 22:36:00

This Week in Logic at CUNY:

- - - - Monday, Oct 14, 2024 - - - -

Rutgers Logic Seminar
Monday October 13, 3:30pm, Rutgers University, Hill Center, Hill 705

Slawomir Solecki, Cornell
From set theory to combinatorics of simplicial maps

CUNY GRADUATE CENTER CLOSED TODAY

- - - - Tuesday, Oct 15, 2024 - - - -

- - - - Wednesday, Oct 16, 2024 - - - -

- - - - Thursday, Oct 17, 2024 - - - -

- - - - Friday, Oct 18, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 18, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Hanul Jeon, Cornell University
On a cofinal Reinhardt embedding without Powerset

Reinhardt embedding is an elementary embedding from $V$ to $V$ itself, whose existence was refuted under the Axiom of Choice by Kunen's famous theorem. There were attempts to get a consistent version of a Reinhardt embedding, and dropping the Axiom of Powerset is one possibility. Richard Matthews showed that $Z F C + I 1$ proves $Z F C$ without Powerset is consistent with a Reinhardt embedding, but the embedding $j : V \to V$ in the Matthews' model does not satisfy the cofinality (i.e., for every set $a$ there is $b$ such that $a \in j (b)$ ). In this talk, I will show from $Z F C + I 0$ that $Z F C$ without Powerset is consistent with a cofinal Reinhardt embedding.

Logic Workshop
CUNY Graduate Center
Friday October 18, 2:00pm-3:30pm, Room 4419

Brian Wynne, CUNY
Old and new decidability results for theories of Abelian lattice-ordered groups

An Abelian lattice-ordered group (l-group) is an Abelian group with a lattice order that is invariant under translations. Examples include $C (X)$ , the set of continuous real-valued functions on a topological space $X$ with pointwise operations and order, the $L p$ spaces, and certain spaces of measures. After surveying some of the known decidability results for various classes of l-groups, I will present new decidability results concerning existentially closed l-groups.

Next Week in Logic at CUNY:

- - - - Monday, Oct 21, 2024 - - - -

Rutgers Logic Seminar
Monday October 21, 3:30pm, Rutgers University, Hill Center, Hill 705

Jason Block, CUNY
Elementarity of Subgroups and Complexity of Theories for Profinite Groups

Logic and Metaphysics Workshop
Date: Monday, October 21, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Thomas M. Ferguson (Rensselaer).
Title: Qua, per se, and other topic-transformative operators

Abstract: Recent work challenging principles of topic transparency in topic-sensitive logics has relied on providing accounts of connectives that are topic-transformative, that is, which non-trivially influence the overall topic assigned to a complex. This leads naturally to the question of what operators in natural language might also act as topic-transformative functions. This talk reviews work in progress studying “qua”, “per se”, and other topic-transformative operators. After discussing ways to analyze these operators, we will emphasize how such analyses are likely to assist in a parallel project of updating Richard Sylvan’s work on relevant containment logic.

Note: This is joint work with Pietro Vigiani (Pisa) and Jitka Kadlečková (Rensselaer).

- - - - Tuesday, Oct 22, 2024 - - - -

- - - - Wednesday, Oct 23, 2024 - - - -

- - - - Thursday, Oct 24, 2024 - - - -

- - - - Friday, Oct 25, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, October 25, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Stefan Geschke University of Hamburg

Logic Workshop
CUNY Graduate Center
Friday October 25, 2:00pm-3:30pm, Room 4419

Hans Schoutens, CUNY
Computing away negation using ancients: from existential to Diophantine sentences

Last semester, I discussed geometric methods for decidability over a complete discrete valuation ring (DVR) in equal characteristic, suggesting that these methods could be applied effectively. In this talk, I aim to clarify the computability issues surrounding this topic while at the same time shifting focus to the case of mixed characteristic. Whereas quantifier elimination (QE) results are established for p-adic numbers, the general landscape remains less explored. I will demonstrate that for any existential sentence over a computable ring, we can effectively construct a positive existential (or Diophantine) sentence which is logically equivalent to the original in every excellent Henselian DVR containing the ring. This construction hinges on Resolution of Singularities, which is feasible in characteristic zero.

Furthermore, I will utilize ultraproducts, specifically the protoproduct variant, to show how Diophantine statements over a DVR can be reduced to those over a residue ring. Since the residue ring is Artinian—and in the case of p-adics, even finite—the associated problems become significantly more manageable. However, it is important to note that this approach does not yet yield a general QE result, as it applies only to sentences, not formulas. The challenge lies in the dependence of certain effective bounds on parameters. I will provide insights into how to derive a bound based on a refined notion of complexity within the equational system—beyond simply considering its degree—using ultraproducts. Additionally, I will address a request from the audience in my last talk by demonstrating that this bound is indeed effective.

And somehow it will also require some delving into the theory of Witt vectors and ancient elements, as I will explain.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Wednesday seminar

Prague Set Theory Seminar

10/13/2024 13:55:59

Dear all, The seminar meets on Wednesday October 16th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Francisco Santiago Nieto de la Rosa -- How to preserve multiple gaps Gaps appear through mathematics many times, in specific in set theory. They are useful, for example to prove that the boolean algebra p(\omega)/fin is not complete. Todorcevic and Aviles introduced a multidimensional generalization. In this talk we will present it, some classical results and conditions to preserve it with a forcing notion. Best, David

KGRC Set Theory talk October 17

Kurt Godel Research Center

10/11/2024 6:38:05

KGRC/Institute of Mathematics invites you to the following talk: Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, October 17, 11:30am--1:00pm, hybrid mode "The classification problem for extensions of torsion-free abelian groups " M. Casarosa (U Paris Cité, FR and U Bologna, IT) In this talk, I discuss the potential Borel complexity of the isomorphism relation for short exact sequences of countable torsion-free abelian groups. For this, we use both set-theoretic methods (in particular the theory of groups with a Polish cover and the notion of Solecki subgroups) and some categorical tools. One of the results is that for a certain class of groups $A$ we can find $C$ such that the classification problem corresponding to $\mathbf{Ext}(C,A)$ can have arbitrarily high potential Borel complexity. I will also present some results on the low-complexity cases and, time permitting, discuss the problem in the case of rigid groups. This is a work in progress with Martino Lupini. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Updates at https://kgrc.univie.ac.at/eventsnews/ -- ________________________________________________ Institute of Mathematics (Kurt Goedel Research Center) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0) 1 4277-50501

Set theory and topology seminar 15.10.2024 Piotr Borodulin-Nadzieja

Wrocław Set Theory Seminar

10/10/2024 12:10:53

I am happy to announce that at the seminar in set theory and topology (on Tuesday 15.10.2024 at 17:15 in room 60? (Mathematical Institute of Wrocław University) the lecture:

"On Banach spaces induced by graphs"

will be presented by

Piotr Borodulin-Nadzieja

Abstract:

I will present a way to define a pair of Banach spaces out of an infinite graph with some examples. I will show a combinatorial characterization of those graphs which induce pairs which are dual in a geometric sense.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You

Szymon Żeberski

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

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

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

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

Logic Seminar Wed 9 Oct 2024 17:00 hrs at NUS

NUS Logic Seminar

10/7/2024 19:17:34

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 9 Oct 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Athipat Thamrongthanyalak Title: Tame expansions of real closed fields and Banach fixed point property URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html In this talk, we study a converse of the Banach fixed point theorem and its connection to tameness in expansions of a real closed field. Let R be a definably complete expansion of a real closed field. We say that R has the BFPP (short for, Banach fixed point property) when, for every locally closed definable set E, if every contraction on E has a fixed point, then E is closed. In this talk, we prove that if R has an o-minimal open core, then R has the BFPP; and if R has the BFPP, then R has a locally o-minimal open core.

Wednesday seminar

Prague Set Theory Seminar

10/6/2024 15:57:13

Dear all, The seminar meets on Wednesday October 9th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Higher-dimensional coherence We present some recent results about higher-dimensional analogues of coherent Aronszajn trees, focusing in particular on two-dimensional objects at aleph_2. Guided by an analogy with the theory of (one-dimensional) coherent Aronszajn trees at aleph_1, we will show that there are many situations in which two-dimensional coherent Aronszajn trees provably exist at aleph_2, but we will also show that these objects are typically quite fragile under forcing, indicating a limit to the extent of this analogy. This is joint work with Jeffrey Bergfalk and Jing Zhang. Best, David

This Week in Logic at CUNY (heads up, no email next week)

This Week in Logic at CUNY

9/29/2024 22:44:00

Hi everyone,

I'll be traveling next weekend, so I won't be able to send out This Week in Logic on 10/6. Regular mailings will resume the following week, Sunday 10/13.

Apologies for any inconvenience,

Jonas

This Week in Logic at CUNY:

- - - - Monday, Sep 30, 2024 - - - -

Rutgers Logic Seminar
Monday September 30, 3:30pm, Rutgers University, Hill Center, Hill 705

Su Gao, University of North Texas
Extremely amenable automorphism groups of countable structures

Logic and Metaphysics Workshop
Date: Monday,September 30, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Daniel West (CUNY)
Title: The disjunction property for operational relevance logics

Abstract: A logic has the disjunction property just in case whenever a disjunction is valid, at least one of its disjuncts is valid. The disjunction property is important to constructivists and is a well-known feature of intuitionistic logic. In this talk I present joint work with Yale Weiss in which we use model-theoretic techniques to show that the disjunction property also holds in Urquhart’s operational relevance logics. This is a known result in the case of the positive semilattice logic, but the proof is quite different, being proof-theoretic rather than semantic. These results suggest that operational relevance logics merit further attention from a constructivist perspective. Along the way, we also provide a novel proof that the disjunction property holds in intuitionistic logic.

Note: This is joint work with Yale Weiss (CUNY).

- - - - Tuesday, Oct 1, 2024 - - - -

- - - - Wednesday, Oct 2, 2024 - - - -

NO CLASSES SCHEDULED - CUNY GRADUATE CENTER

- - - - Thursday, Oct 3, 2024 - - - -

NO CLASSES SCHEDULED - CUNY GRADUATE CENTER

- - - - Friday, Oct 4, 2024 - - - -

NO CLASSES SCHEDULED - CUNY GRADUATE CENTER

Next Week in Logic at CUNY:

- - - - Monday, Oct 7, 2024 - - - -

Rutgers Logic Seminar
Monday October 7, 3:30pm, Rutgers University, Hill Center, Hill 705

James Walsh, NYU

Logic and Metaphysics Workshop
Date: Monday, October 7, 4.15-6.15pm (NY time), GC 4419

Cian Dorr (NYU) and Matt Mandelkern (NYU)

Title: The logic of sequences

Abstract: In the course of proving a tenability result about the probabilities of conditionals, van Fraassen (1976) introduced a semantics for conditionals based on ω-sequences of worlds, which amounts to a particularly simple special case of ordering semantics for conditionals. On that semantics, ‘If p, then q’ is true at an ω-sequence just in case q is true at the first tail of the sequence where p is true (if such a tail exists). This approach has become increasingly popular in recent years. However, its logic has never been explored. We axiomatize the logic of ω-sequence semantics, showing that it is the result of adding two new axioms to Stalnaker’s logic C2: one, Flattening, which is prima facie attractive, and a second, Sequentiality, which is complex and difficult to assess. We also show that when sequence semantics is generalized to arbitrary (transfinite) ordinal sequences, the result is the logic that adds only Flattening to C2. We also explore the logics of a few other interesting restrictions of ordinal sequence semantics, and explore whether sequence semantics is motivated by probabilistic considerations, answering, pace van Fraassen, in the negative.

- - - - Tuesday, Oct 8, 2024 - - - -

- - - - Wednesday, Oct 9, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Date and Time: Wednesday October 9, 2024, 7:00 - 8:30 PM. ZOOM TALK (contact N Yanofsky for zoom link)

Speaker: Sam McCrosson, Montana State University.
Title: Exodromy.

Abstract: A favorite result of first semester algebraic topology is the “monodromy theorem,” which states that for a suitable topological space X, there is a triple equivalence between the categories of covering spaces of X, sets with an action from the fundamental group of X, and locally constant sheaves on X. This result has recently been upgraded by MacPherson and others to a stratified setting, where the underlying space may be carved into a poset of subspaces. In this talk, we’ll look at the main ingredients of the so-called “exodromy theorem,” reviewing stratified spaces and developing “constructible sheaves” and the “exit-path category” along the way.

- - - - Thursday, Oct 10, 2024 - - - -

- - - - Friday, Oct 11, 2024 - - - -

NO CLASSES SCHEDULED - CUNY GRADUATE CENTER

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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KGRC Set Theory talks September 30 - October 4

Kurt Godel Research Center

9/27/2024 3:54:27

KGRC/Institute of Mathematics invites you to the following Set Theory talks: Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Tuesday, October 1, 3pm--4:30pm, hybrid mode "Coding into the orbits of cofinitary permutations" L. Schembecker (U Hamburg, DE) In my talk I will give an introduction to (maximal) cofinitary groups (mcg's) and their corresponding cardinal characteristic $\mathfrak{a}_g$. I will present a notion of tightness for mcg's which implies the forcing indestructibility for various types of tree forcings, allowing us to prove that $\mathfrak{a}_g$ stays small in various models. Further, I will explain Zhang's forcing - the central forcing notion in context of mcg's - and show how one can adapt this forcing by some new coding techniques in order to construct co-analytic tight cofinitary groups. If time permits, we will see how these result may be combined with recent developments regarding projective well-orders and cardinal characteristics to obtain: Consistently, $\mathfrak{a}_g = \mathfrak{d} < \mathfrak{c} = \aleph_2$ alongside the existence of a $\Delta^1_3$-wellorder of the reals and a co-analytic witness for $\mathfrak{a}_g$. This is joint work with Vera Fischer and David Schrittesser. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, October 3, 11:30am--1:00pm, hybrid mode "Measures on omega" P. Borodulin-Nadzieja (U Wroclaw, PL) A (finitely additive) measure on omega is a natural generalization of an ultrafilter. In my talk I will discuss how to upgrade some classical notions studied for ultrafilters (such as P-points, Q-points, Rudin-Blass ordering) to the measure context. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, October 3, 3:00pm--3:50pm, hybrid mode "Definable hypergraphs on large spaces" P. Schlicht (U Wien) The open graph dichotomy states that the complete graph on the Cantor space is least among open graphs on analytic sets with respect to the ordering given by continuous graph homomorphisms. Ben Miller used dichotomies of this form to prove many interesting theorems in descriptive set theory. I will survey some results in this area focusing on generalised descriptive set theory, games and the Wadge hierarchy, and consider combinatorial counterparts to dichotomies such as the open graph axiom. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Updates at https://kgrc.univie.ac.at/eventsnews/. -- ________________________________________________ Institute of Mathematics (Kurt Goedel Research Center) University of Vienna Kolingasse 14-16 1090 Vienna, Austria Phone: +43/ (0) 1 4277-50501

Wednesday seminar

Prague Set Theory Seminar

9/26/2024 8:56:21

Dear all, The seminar meets on Wednesday October 2nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Pedro Marun -- MM for posets of size aleph_1 While the Proper Forcing Axiom (PFA) and its strengthening Martin’s Maximum (MM) have considerable large cardinal strength, the same is not true for posets of size aleph_1. If we write FA(aleph_1) for the restricted axiom, then Shelah showed that PFA(aleph_1) is relatively consistent with ZFC, while the consistency of MM(aleph_1) follows from an inaccessible. Mota asked whether Shelah’s inaccessible could be taken away. In joint work with Dobrinen, Krueger, Mota and Zapletal, we showed that the inaccessible is not necessary. The goal of this talk is to give (sketch?) the proof of this fact. We will also mention some open problems. Best, David

Wednesday seminar

Prague Set Theory Seminar

9/24/2024 3:49:33

Dear all, The seminar meets on Wednesday September 25th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Chodounsky -- Big Ramsey degrees of the pseudotree Yet again, I will talk about the big Ramsey degrees of the (binary) pseudotree, i.e. the countable universal homogeneous meet-tree, also the Fraisse limit of the class of finite meet trees (and its binary analogue). I plan to sketch again the proof that two element anti-chains do not have finite big Ramsey degree, and I will introduce some ideas for proving that finite chains do have finite big Ramsey degrees. This will be a 'work in progress' talk which make take unexpected turns and stops. Best, David

This Week in Logic at CUNY

9/22/2024 22:31:00

This Week in Logic at CUNY:

- - - - Monday, Sep 23, 2024 - - - -

Rutgers Logic Seminar
Monday September 23, 3:30pm, Rutgers University, Hill Center, Hill 705

Russell Miller, CUNY
Countable reductions in computable structure theory

Logic and Metaphysics Workshop
Date: Monday,September 23, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Rohit Parikh (CUNY)
Title: Value and freedom

Abstract: In order to decide how good a society is, we need some measure of goodness. And the goodness of a society is typically obtained by somehow summing up the well beings of its members. Various approaches include Utilitarianism and Rawlsianism as well as the Leximin approach suggested by Amartya Sen. But Sen and Nussbaum have suggested that the Capability of an individual, what the individual can do, should be the real measure of well being. Another issue is that of freedom. My freedom can be diminished by some restrictive laws. But it can also be diminished by some handicap, or by certain social methods not being available. How to measure the amount of freedom I have? Is it simply the number of options I have, or does the value of the options also matter? And what is the mathematics of freedom?

Note: An extended abstract is available here.

- - - - Tuesday, Sep 24, 2024 - - - -

- - - - Wednesday, Sep 25, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Date and Time: Wednesday September 25, 2024, 7:00 - 8:30 PM. IN-PERSON TALK, Room 6417

Speaker: Noah Chrein, University of Maryland

Title: A formal category theory for oo-T-multicategories.

Abstract: We will explore a framework for oo-T-multicategories. To begin, we build a schema for multicategories out of the simplex schema and the monoid schema. The multicategory schema, D_m, inherits the structure of a monad from the +1 monad on the monoid schema. Simplicial T-multicategories are monad preserving functors out of the multicategory schema, [D_m, T], into another monad T. The framework is larger than just [D_m,T]. A larger structure describes notions of yoneda lemma and fibration. Inner fibrant, simplicial T-multicategories are oo-T-multicategories. oo-T-multicategories generalize oo-categories and oo-operads: oo-operads are fm-multicategories, oo-categories are Id-multicategories.

We use this framework to study oo-fc-multicategories, or "oo - virtual double categories". In general, under various assumptions on T (which hold for fc), the collection of oo-T-multicategories [D_m, T] has other useful structure. One such structure is a join operation. This join operation points towards a synthetic definition of op/cartesian cells, which we hope will model oo-virtual equipments. If there is time, I will explain the motivation for this study as it relates to ontologies, meta-theories and type theories.

- - - - Thursday, Sep 26, 2024 - - - -

- - - - Friday, Sep 27, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, September 6, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Takashi Yamazoe, Kobe University
Cichoń's maximum with the uniformity and the covering of the $σ$ -ideal $E$ generated by closed null sets

Let $E$ denote the $σ$ -ideal generated by closed null sets on $R$ . We show that the uniformity and the covering of $E$ can be added to Cichoń's maximum with distinct values, more specifically, it is consistent that $ℵ 1 < a d d (N) < c o v (N) < b < n o n (E) < n o n (M) < c o v (M) < c o v (E) < d < n o n (N) < c o f (N) < 2 ℵ 0$ holds.

Logic Workshop
CUNY Graduate Center
Friday September 27, 2:00pm-3:30pm, Room 4419

Victoria Gitman, CUNY
Baby measurable cardinals

Measurable cardinals and other large cardinals on the larger side of things are characterized by the existence of elementary embeddings $j : V \to M$ from the universe $V$ of sets into a transitive submodel $M$ . The clear pattern the large cardinals in that region follow is that the closer the submodel $M$ is to $V$ the stronger the large cardinal notion. Smaller large cardinals, such as weakly compact or Ramsey cardinals, are known chiefly for their combinatorial properties, such as the existence of large homogeneous sets for colorings. But, it turns out that they too have elementary embeddings characterizations with embeddings on the correspondingly small models $M$ of (a fragment) of set theory (usually $Z F C -$ , the theory $Z F C$ with powerset axiom removed). Elementary embeddings of $V$ are often by-definable with the existence of certain ultrafilters or systems of ultrafilters. The classical example is that $κ$ is measurable if and only if there is a $κ$ -complete ultrafilter on $κ$ . The model $M$ is then the transitive collapse of the ultrapower of $V$ by $U$ . The connection between elementary embedding and ultrafilters also exists in the case of the small elementary embeddings. A typical elementary embedding characterization of a small large cardinal $κ$ follows the following template: for every $A \subseteq κ$ , there is a (technical condition) model $M$ , with $A \in M$ , for which there is an $M$ -ultrafilter $U$ on $κ$ with (technical properties). A subset $U \subseteq P (κ) \cap M$ is an $M$ -ultrafilter if the structure $⟨ M, \in, U ⟩$ , with a predicate for $U$ , satisfies that $U$ is a $κ$ -complete ultrafilter on $κ$ , meaning that $U$ measures all the sets in $M$ and its completeness applies to sequences that are elements of $M$ . The reason we need to add a predicate for $U$ is that in most interesting case, and in contrast to the situation with measurable cardinals, $U$ is not an element of $M$ (indeed in most cases, $P (κ)$ does not exist in $M$ ). While the structure $M$ usually satisfies some large fragment of $Z F C$ , once, we add a predicate for the $M$ -ultrafilter $U$ , the structure $⟨ M, \in, U ⟩$ can fail to satisfy even $Σ 0$ -separation. In this talk, I will discuss how smaller large cardinals follow the pattern that the more set theory the structure $⟨ M, \in, U ⟩$ satisfies the stronger the resulting large cardinal notion. I will use these observations to introduce a new hierarchy of large cardinals between Ramsey and measurable cardinals. This is joint work with Philipp Schlicht, based on earlier work by Bovykin and McKenzie.

Next Week in Logic at CUNY:

- - - - Monday, Sep 30, 2024 - - - -

Rutgers Logic Seminar
Monday September 30, 3:30pm, Rutgers University, Hill Center, Hill 705

Su Gao, University of North Texas
Extremely amenable automorphism groups of countable structures

Logic and Metaphysics Workshop
Date: Monday,September 30, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Daniel West (CUNY)
Title: The disjunction property for operational relevance logics

Abstract: A logic has the disjunction property just in case whenever a disjunction is valid, at least one of its disjuncts is valid. The disjunction property is important to constructivists and is a well-known feature of intuitionistic logic. In this talk I present joint work with Yale Weiss in which we use model-theoretic techniques to show that the disjunction property also holds in Urquhart’s operational relevance logics. This is a known result in the case of the positive semilattice logic, but the proof is quite different, being proof-theoretic rather than semantic. These results suggest that operational relevance logics merit further attention from a constructivist perspective. Along the way, we also provide a novel proof that the disjunction property holds in intuitionistic logic.

Note: This is joint work with Yale Weiss (CUNY).

- - - - Tuesday, Oct 1, 2024 - - - -

- - - - Wednesday, Oct 2, 2024 - - - -

NO CLASSES SCHEDULED - CUNY GRADUATE CENTER

- - - - Thursday, Oct 3, 2024 - - - -

NO CLASSES SCHEDULED - CUNY GRADUATE CENTER

- - - - Friday, Oct 4, 2024 - - - -

NO CLASSES SCHEDULED - CUNY GRADUATE CENTER

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

This Week in Logic at CUNY

9/15/2024 22:37:00

This Week in Logic at CUNY:

- - - - Monday, Sep 16, 2024 - - - -

Rutgers Logic Seminar
Monday September 16, 3:30pm, Rutgers University, Hill Center, Hill 705
Maxwell Levine, University of Freiburg
Namba Forcing, Minimality, and Approximations

Logic and Metaphysics Workshop
Date: Monday,September 16, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Speaker: Mel Fitting (CUNY)
Title: Simple tableaus for simple logics

Abstract: Consider those many-valued logic models in which the truth values are a lattice that supplies interpretations for the logical connectives of conjunction and disjunction, and which has a De Morgan involution supplying an interpretation for negation. Assume the set of designated truth values is a prime filter in the lattice. Each of these structures determines a simple many-valued logic. We show there is a single Smullyan style signed tableau system appropriate for all of the logics these structures determine. Differences between the logics are confined entirely to tableau branch closure rules. Completeness, soundness, and interpolation can be proved in a uniform way for all cases. Since branch closure rules have a limited number of variations, in fact all the semantic structures determine just four different logics, all well-known ones. Asymmetric logics such as strict/tolerant, ST, also share all the same tableau rules, but differ in what constitutes an initial tableau. It is also possible to capture the notion of anti-validity using the same set of tableau rules. Thus a simple set of tableau rules serves as a unifying and classifying device for a natural and simple family of many-valued logics.

- - - - Tuesday, Sep 17, 2024 - - - -

- - - - Wednesday, Sep 18, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Date and Time: Wednesday September 18, 2024, 7:00 - 8:30 PM. IN-PERSON TALK, Room 6417

Speaker: Jake Araujo-Simon, Cornell Tech.

Title: Categorifying the Volterra series: towards a compositional theory of nonlinear signal processing.

Abstract:The Volterra series is a model of nonlinear behavior that extends the convolutional representation of linear and time-invariant systems to the nonlinear regime. Though well-known and applied in electrical, mechanical, biomedical, and audio engineering, its abstract and especially compositional properties have been less studied. In this talk, we present an approach to categorifying the Volterra series, in which a Volterra series is defined as a functor on a category of signals and linear maps, a morphism between Volterra series is a lens map and natural transformation, and together, Volterra series and their morphisms assemble into a category, which we call Volt. We study three monoidal structures on Volt, and outline connections of our work to the field of time-frequency analysis. We also include an audio demo.

Paper link: https://arxiv.org/abs/2308.07229

- - - - Thursday, Sep 19, 2024 - - - -

- - - - Friday, Sep 20, 2024 - - - -

Next Week in Logic at CUNY:

- - - - Monday, Sep 23, 2024 - - - -

Rutgers Logic Seminar
Monday September 9, 3:30pm, Rutgers University, Hill Center, Hill 705

Russell Miller, CUNY
Countable reductions in computable structure theory

Logic and Metaphysics Workshop
Date: Monday,September 23, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419

Rohit Parikh (CUNY)
Title: Value and freedom

Abstract: In order to decide how good a society is, we need some measure of goodness. And the goodness of a society is typically obtained by somehow summing up the well beings of its members. Various approaches include Utilitarianism and Rawlsianism as well as the Leximin approach suggested by Amartya Sen. But Sen and Nussbaum have suggested that the Capability of an individual, what the individual can do, should be the real measure of well being. Another issue is that of freedom. My freedom can be diminished by some restrictive laws. But it can also be diminished by some handicap, or by certain social methods not being available. How to measure the amount of freedom I have? Is it simply the number of options I have, or does the value of the options also matter? And what is the mathematics of freedom?

Note: An extended abstract is available here.

- - - - Tuesday, Sep 24, 2024 - - - -

- - - - Wednesday, Sep 25, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Date and Time: Wednesday September 25, 2024, 7:00 - 8:30 PM. IN-PERSON TALK, Room 6417

Speaker: Noah Chrein, University of Maryland

Title: A formal category theory for oo-T-multicategories.

Abstract: We will explore a framework for oo-T-multicategories. To begin, we build a schema for multicategories out of the simplex schema and the monoid schema. The multicategory schema, D_m, inherits the structure of a monad from the +1 monad on the monoid schema. Simplicial T-multicategories are monad preserving functors out of the multicategory schema, [D_m, T], into another monad T. The framework is larger than just [D_m,T]. A larger structure describes notions of yoneda lemma and fibration. Inner fibrant, simplicial T-multicategories are oo-T-multicategories. oo-T-multicategories generalize oo-categories and oo-operads: oo-operads are fm-multicategories, oo-categories are Id-multicategories.

We use this framework to study oo-fc-multicategories, or "oo - virtual double categories". In general, under various assumptions on T (which hold for fc), the collection of oo-T-multicategories [D_m, T] has other useful structure. One such structure is a join operation. This join operation points towards a synthetic definition of op/cartesian cells, which we hope will model oo-virtual equipments. If there is time, I will explain the motivation for this study as it relates to ontologies, meta-theories and type theories.

- - - - Thursday, Sep 26, 2024 - - - -

- - - - Friday, Sep 27, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday September 27, 2:00pm-3:30pm, Room 4419

Victoria Gitman, CUNY

TBA

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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Logic Seminar 18 September 2024 16:45 hrs at NUS by Le Quy Thuong

NUS Logic Seminar

9/15/2024 22:49:51

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 18 September 2024, 16:45 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Le Quy Thuong Title: Motivic integration in valued fields and applications to singularity theory Abstract: Since 1995, motivic integration has been a powerful tool in algebraic geometry and other branches of mathematics. In particular, it has many important applications to singularity theory. For instance, Denef-Loeser around 2000 gave a breakthrough point of view in the study of singularities, by introducing the so-called motivic Milnor fiber, with the philosophy that this is a motivic incarnation of the classical Milnor fiber. One shows that many singularity invariants can be easily recovered from motivic zeta function and motivic Milnor fiber employing an appropriate Hodge realization. Furthermore, there are important problems concerning singularity theory such as monodromy conjecture, the integral identity conjecture, and the Thom-Sebastiani theorem that are waiting for new methods in motivic integration to have a solution. In this talk, we will describe some surprising interactions between motivic integration, model theory and singularity theory that lead to our proofs for the integral identity conjecture, and the motivic Thom-Sebastiani theorem, as well as other applications to singularities. The talk will avoid technical aspects and emphasize key ideas in motivic integration and singularity theory, which may be friendly to a general audience. Note that this week the seminar starts 15 minutes earlier than usual. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

9/8/2024 22:47:00

This Week in Logic at CUNY:

- - - - Monday, Sep 9, 2024 - - - -

Rutgers Logic Seminar
Monday September 9, 3:30pm Hill Center, Hill 705
Corey Switzer, KGRC
Weak and Strong Variants of Baumgartner's Axiom for Polish Spaces

Logic and Metaphysics Workshop
Date: Monday,September 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Speaker: Hartry Field (NYU)
Title: Well-behaved truth

Abstract: Common-sense reasoning with truth involves both the use of classical logic and the assumption of the transparency of truth (the equivalence between a sentence and the attribution of truth to it). The semantic paradoxes show that at least one of these must go, and different theorists make different choices. But whatever one’s choice, it’s valuable to carve out one or more domains where both classical logic and transparency can be assumed; domains where everything is *well-behaved*. In this talk I’ll explore a method of adding a predicate of well-behavedness to various truth theories, which works for both classical and nonclassical theories (including non-classical theories with special conditionals). With such a predicate, one can reason more easily, and formulate and prove generalizations that are unavailable without such a predicate. Besides their intrinsic interest, these generalizations greatly increase the proof-theoretic strength of axiomatic theories. (There are some previous proposals for adding a well-behavedness predicate to specific classical theories, and others for adding one to non-classical theories without special conditionals. The current proposal, besides being general, is also more satisfactory in the individual cases, and is the only one I know of for non-classical theories with conditionals.)

- - - - Tuesday, Sep 10, 2024 - - - -

- - - - Wednesday, Sep 11, 2024 - - - -

- - - - Thursday, Sep 12, 2024 - - - -

- - - - Friday, Sep 13, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday September 13, 2:00pm-3:30pm, Room 4419

David Marker, University of Illinois at Chicago
Rigid real closed fields

Shelah showed that it is consistent that there are uncountable rigid non-archimedean real closed fields and, later, he and Mekler proved this in . Answering a question of Enayat, Charlie Steinhorn and I show that there are countable rigid non-archimedean real closed fields by constructing one of transcendence degree two.

Next Week in Logic at CUNY:

- - - - Monday, Sep 16, 2024 - - - -

Rutgers Logic Seminar
Monday September 9, 3:30pm, Rutgers University, Hill Center, Hill 705
Maxwell Levine, University of Freiburg
Namba Forcing, Minimality, and Approximations

Logic and Metaphysics Workshop
Date: Monday,September 16, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Speaker: Mel Fitting (CUNY)
Title: Simple tableaus for simple logics

Abstract: Consider those many-valued logic models in which the truth values are a lattice that supplies interpretations for the logical connectives of conjunction and disjunction, and which has a De Morgan involution supplying an interpretation for negation. Assume the set of designated truth values is a prime filter in the lattice. Each of these structures determines a simple many-valued logic. We show there is a single Smullyan style signed tableau system appropriate for all of the logics these structures determine. Differences between the logics are confined entirely to tableau branch closure rules. Completeness, soundness, and interpolation can be proved in a uniform way for all cases. Since branch closure rules have a limited number of variations, in fact all the semantic structures determine just four different logics, all well-known ones. Asymmetric logics such as strict/tolerant, ST, also share all the same tableau rules, but differ in what constitutes an initial tableau. It is also possible to capture the notion of anti-validity using the same set of tableau rules. Thus a simple set of tableau rules serves as a unifying and classifying device for a natural and simple family of many-valued logics.

- - - - Tuesday, Sep 17, 2024 - - - -

- - - - Wednesday, Sep 18, 2024 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Date and Time: Wednesday September 18, 2024, 7:00 - 8:30 PM. IN-PERSON TALK
Room 5417 (not the usual Room 6417)

Speaker: Jake Araujo-Simon, Cornell Tech.

Title: Categorifying the Volterra series: towards a compositional theory of nonlinear signal processing.

- - - - Thursday, Sep 19, 2024 - - - -

- - - - Friday, Sep 20, 2024 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

UPDATE: This Week in Logic - today's Logic Workshop is in GC 4419

This Week in Logic at CUNY

9/6/2024 7:16:03

Please note, the room for the Logic Workshop, including today's talk at has been changed to 4419.

Best,

Jonas

This Week in Logic at CUNY:

- - - - Thursday, Sep 05, 2024 - - - -

- - - - Friday, Sep 06, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, September 6, 11:00am NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Corey Switzer, Kurt Gödel Research Center
Reflecting Ordinals and Forcing

Let and either or . An ordinal is called -reflecting if for each and each -formula if then there is a so that where here refers to full second order logic. The least -reflecting ordinal is called and the least -ordinal is called . These ordinals provably exist and are countable (for all ). They arise naturally in proof theory, particularly in calibrating consistency strength of strong arithmetics and weak set theories. Moreover, surprisingly, their relation to one another relies heavily on the background set theory. If then for all we have (due to Cutland) while under PD for all we have if and only if is even (due to Kechris).
Surprisingly nothing was known about these ordinals in any model which satisfies neither nor PD. In this talk I will sketch some recent results which aim at rectifying this. In particular we will show that in any generic extension by any number of Cohen or Random reals, a Sacks, Miller or Laver real, or any lightface, weakly homogeneous Borel ccc forcing notion agrees with about which ordinals are -reflecting (for any and ). Meanwhile, in the generic extension by collapsing many interesting things happen, not least amongst them that and are increased - yet still below for . Along the way we will discuss the plethora of open problems in this area. This is joint work with Juan Aguilera.

Logic Workshop
CUNY Graduate Center
Friday September 6, 2:00pm-3:30pm, Room 4419

Corey Switzer, Kurt Gödel Research Center
Weak and Strong Variants of Baumgartner's Axiom for Polish Spaces

(One version of) Cantor's second best theorem states that every pair of countable, dense sets of reals are isomorphic as linear orders. From the perspective of set theory it's natural to ask whether some variant of this theorem can hold consistently when 'countable' is replaced by 'uncountable'. This was shown in the affirmative by Baumgartner in 1973 who showed the consistency of 'all -dense sets of reals are order isomorphic' where a set is -dense for a cardinal if its intersection with any open interval has size . The above became known as Baumgartner's axiom, denoted BA, and is an important axiom in both combinatorial set theory and set theoretic topology. BA has natural higher dimensional analogues - i.e., statements with the same relation to that BA has to . It is a long standing open conjecture of Steprāns and Watson that BA implies its higher dimensional analogues.

In the talk I will describe some attempts to break the ice on this open problem mostly by looking at a family of weaker and stronger variants of BA and investigating their combinatorial, analytic and topological consequences. We will show that while some weak variants of BA have all the same consequences as BA, even weaker ones do not. Meanwhile a strengthening of BA for Baire and Polish space gives much more information.

Next Week in Logic at CUNY:

- - - - Monday, Sep 9, 2024 - - - -

Rutgers Logic Seminar
Monday September 9, 3:30pm Hill Center, Hill 705
Corey Switzer, KGRC
Weak and Strong Variants of Baumgartner's Axiom for Polish Spaces

Logic and Metaphysics Workshop
Date: Monday,September 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Speaker: Hartry Field (NYU)
Title: Well-behaved truth

Abstract: Common-sense reasoning with truth involves both the use of classical logic and the assumption of the transparency of truth (the equivalence between a sentence and the attribution of truth to it). The semantic paradoxes show that at least one of these must go, and different theorists make different choices. But whatever one’s choice, it’s valuable to carve out one or more domains where both classical logic and transparency can be assumed; domains where everything is *well-behaved*. In this talk I’ll explore a method of adding a predicate of well-behavedness to various truth theories, which works for both classical and nonclassical theories (including non-classical theories with special conditionals). With such a predicate, one can reason more easily, and formulate and prove generalizations that are unavailable without such a predicate. Besides their intrinsic interest, these generalizations greatly increase the proof-theoretic strength of axiomatic theories. (There are some previous proposals for adding a well-behavedness predicate to specific classical theories, and others for adding one to non-classical theories without special conditionals. The current proposal, besides being general, is also more satisfactory in the individual cases, and is the only one I know of for non-classical theories with conditionals.)

- - - - Tuesday, Sep 10, 2024 - - - -

- - - - Wednesday, Sep 11, 2024 - - - -

- - - - Thursday, Sep 12, 2024 - - - -

- - - - Friday, Sep 13, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday September 13, 2:00pm-3:30pm, Room 4419

David Marker, University of Illinois at Chicago
Rigid real closed fields

Shelah showed that it is consistent that there are uncountable rigid non-archimedean real closed fields and, later, he and Mekler proved this in . Answering a question of Enayat, Charlie Steinhorn and I show that there are countable rigid non-archimedean real closed fields by constructing one of transcendence degree two.

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Logic Seminar 11 September 2024 17:00 hrs by Kihara Takayuki at NUS

NUS Logic Seminar

9/6/2024 5:50:14

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 11 September 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Kihara Takayuki Title: Degrees of unsolvability of natural problems: A realizability-theoretic approach Abstract: The theories of degrees of unsolvability and realizability interpretation both have long histories, having both been born in the 1940s. S. C. Kleene was a key figure who led the development of both theories. Despite having been developed by the same person, there seems to have been little deep mixing of these theories until recently. In this talk, we will reconstruct the theory of degrees of unsolvability from the perspective of realizability theory. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar

9/5/2024 9:34:21

Dear all, The seminar meets on Wednesday September 11th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Pedro Marun -- Labelled sets A theorem of Dilworth asserts that, if a poset P has no antichains of size m+1, where m is a natural number, then P can be written as a union of m many chains. If m is instead an infinite cardinal, then the analogous statement is false, counterexamples were constructed by Perles. In recent work, Abraham and Pouzet gave a basis for the class of such counterexamples, and asked if it could be somewhat simplified. Labelled sets arise in connection with these counterexamples. We show that, when the underlying sets are aleph_1-dense, then any two labelled sets embed into each other. Best, David

This Week in Logic at CUNY

9/4/2024 23:26:44

This initial edition of This Week in Logic at CUNY is going out midweek, but in future our mailings will be on Sunday evenings as in the past. Welcome back, everyone!

Best,

Jonas

This Week in Logic at CUNY:

- - - - Thursday, Sep 05, 2024 - - - -

- - - - Friday, Sep 06, 2024 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, September 6, 11:00am NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.

Corey Switzer, Kurt Gödel Research Center
Reflecting Ordinals and Forcing

Let $n < ω$ and $Γ$ either $Π$ or $Σ$ . An ordinal $α$ is called $Γ 1 n$ -reflecting if for each $β < α$ and each $Γ 1 n$ -formula $φ$ if $L α ⊨ φ (β)$ then there is a $γ \in (β, α)$ so that $L γ ⊨ φ (β)$ where here $⊨$ refers to full second order logic. The least $Σ 1 n$ -reflecting ordinal is called $σ 1 n$ and the least $Π 1 n$ -ordinal is called $π 1 n$ . These ordinals provably exist and are countable (for all $n < ω$ ). They arise naturally in proof theory, particularly in calibrating consistency strength of strong arithmetics and weak set theories. Moreover, surprisingly, their relation to one another relies heavily on the background set theory. If $V = L$ then for all $n < ω$ we have $σ 1 n + 3 < π 1 n + 3$ (due to Cutland) while under PD for all $n < ω$ we have $σ 1 n < π 1 n$ if and only if $n$ is even (due to Kechris).
Surprisingly nothing was known about these ordinals in any model which satisfies neither $V = L$ nor PD. In this talk I will sketch some recent results which aim at rectifying this. In particular we will show that in any generic extension by any number of Cohen or Random reals, a Sacks, Miller or Laver real, or any lightface, weakly homogeneous Borel ccc forcing notion agrees with $L$ about which ordinals are $Γ 1 n$ -reflecting (for any $n$ and $Γ$ ). Meanwhile, in the generic extension by collapsing $ω 1$ many interesting things happen, not least amongst them that $σ 1 n$ and $π 1 n$ are increased - yet still below $ω L 1$ for $n > 2$ . Along the way we will discuss the plethora of open problems in this area. This is joint work with Juan Aguilera.

Logic Workshop
CUNY Graduate Center
Friday September 6, 2:00pm-3:30pm, Room 6417 (NOTICE THE CHANGE! BACK TO OUR PRE-2023 ROOM)

Corey Switzer, Kurt Gödel Research Center
Weak and Strong Variants of Baumgartner's Axiom for Polish Spaces

(One version of) Cantor's second best theorem states that every pair of countable, dense sets of reals are isomorphic as linear orders. From the perspective of set theory it's natural to ask whether some variant of this theorem can hold consistently when 'countable' is replaced by 'uncountable'. This was shown in the affirmative by Baumgartner in 1973 who showed the consistency of 'all $ℵ 1$ -dense sets of reals are order isomorphic' where a set is $κ$ -dense for a cardinal $κ$ if its intersection with any open interval has size $κ$ . The above became known as Baumgartner's axiom, denoted BA, and is an important axiom in both combinatorial set theory and set theoretic topology. BA has natural higher dimensional analogues - i.e., statements with the same relation to $R n$ that BA has to $R$ . It is a long standing open conjecture of Steprāns and Watson that BA implies its higher dimensional analogues.

In the talk I will describe some attempts to break the ice on this open problem mostly by looking at a family of weaker and stronger variants of BA and investigating their combinatorial, analytic and topological consequences. We will show that while some weak variants of BA have all the same consequences as BA, even weaker ones do not. Meanwhile a strengthening of BA for Baire and Polish space gives much more information.

Next Week in Logic at CUNY:

- - - - Monday, Sep 9, 2024 - - - -

Rutgers Logic Seminar
Monday September 9, 3:30pm Hill Center, Hill 705
Corey Switzer, KGRC
Weak and Strong Variants of Baumgartner's Axiom for Polish Spaces

Logic and Metaphysics Workshop
Date: Monday,September 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
Speaker: Hartry Field (NYU)
Title: Well-behaved truth

Abstract: Common-sense reasoning with truth involves both the use of classical logic and the assumption of the transparency of truth (the equivalence between a sentence and the attribution of truth to it). The semantic paradoxes show that at least one of these must go, and different theorists make different choices. But whatever one’s choice, it’s valuable to carve out one or more domains where both classical logic and transparency can be assumed; domains where everything is *well-behaved*. In this talk I’ll explore a method of adding a predicate of well-behavedness to various truth theories, which works for both classical and nonclassical theories (including non-classical theories with special conditionals). With such a predicate, one can reason more easily, and formulate and prove generalizations that are unavailable without such a predicate. Besides their intrinsic interest, these generalizations greatly increase the proof-theoretic strength of axiomatic theories. (There are some previous proposals for adding a well-behavedness predicate to specific classical theories, and others for adding one to non-classical theories without special conditionals. The current proposal, besides being general, is also more satisfactory in the individual cases, and is the only one I know of for non-classical theories with conditionals.)

- - - - Tuesday, Sep 10, 2024 - - - -

- - - - Wednesday, Sep 11, 2024 - - - -

- - - - Thursday, Sep 12, 2024 - - - -

- - - - Friday, Sep 13, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday September 13, 2:00pm-3:30pm, Room 6417 (NOTICE THE CHANGE! BACK TO OUR PRE-2023 ROOM)

Conference

7/15/2024

Kyoto University RIMS Set Theory Workshop 2024 Announcement / Call for Contributions Kyoto University RIMS Workshop: Recent Developments in Axiomatic Set Theory Hybrid workshop Date: Wednesday October 9th to Friday October 11th, 2024 Organizer: Masahiro Shioya (University of Tsukuba) Overview: RIMS Set Theory Workshop is held annually at the Research Institute for Mathematical Sciences, Kyoto University, Japan. It aims to bring together researchers in Set Theory from Japan and abroad and to foster research exchange. We encourage both young researchers and experts to contribute with talks. Any topics in Set Theory and relevant areas, as well as both in-person talks at RIMS and online talks via Zoom, are welcome. Invited Lectures: Monroe Eskew (University of Vienna): Dense ideals Gabriel Goldberg (UC Berkeley): The Ultrapower Axiom Registration through the website https://sites.google.com/view/rims-set-theory-2024/home Registration deadlines: Contributed talks: August 31st, 2024 Attendance in person: August 31st, 2024 Attendance via Zoom: October 7th, 2024

Link to more info

Wednesday seminar

Prague Set Theory Seminar

6/26/2024 9:34:32

Dear all, The seminar meets on Wednesday July 3rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, blue lecture hall, ground floor, rear building. NOTE THE UNUSUAL LOCATION! Program: Jindrich Zapletal -- A convenient axiomatization of the Solovay model I provide a simple forcing-free axiomatization of the choiceless Solovay model, which proves many of its features and features of its generic extensions. It is unlikely that there will be more Wednesday seminars during the rest of July. Seminars in August are uncertain. You might be interested in the Midsummer Combinatorial Workshop which will take place during July 29--August 2nd at Mala Strana, there will be a number of interesting visitors. Best, David

Set theory and topology seminar 25.06.2024 everybody

Wrocław Set Theory Seminar

6/23/2024 6:40:02

I am happy to announce that the last seminar this semester in Set Theory and Topology (on Thuesday 25.06.2024 at 17:15) will take place in

"Forma Płynna Beach Bar"

Plaża miejska, Wybrzeże Wyspiańskiego.

Every participant is the speaker.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You

Szymon Żeberski

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

Wednesday seminar

Prague Set Theory Seminar

6/21/2024 7:57:55

Dear all, The seminar meets on Wednesday June 26th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Tristan Bice -- Constructing Compacta from Posets Trees are commonly used to construct topological spaces from their branches. However, the resulting spaces are usually quite special, e.g. having lots of clopen sets. Our goal is to construct more general (e.g. connected) spaces in a similar way from posets that are still quite 'tree-like'. This leads to a simple construction allowing us to build any second countable compact T_1 space (e.g. any metrisable compactum) from a countable graded poset with finite levels. In particular, this can be used to construct spaces like the pseudoarc and Lelek fan as Fraïssé limits in appropriate categories of graphs with relational morphisms. Continuous maps can also be encoded by certain relations between the posets with potential applications to finding dense and comeagre conjugacy classes of homeomorphisms, again in a simple Fraïssé theoretic way (joint work with Adam Bartoš, Maciej Malicki and Alessandro Vignati). Best, David

Set theory and topology seminar 18.06.2024 Aleksander Cieślak

Wrocław Set Theory Seminar

6/17/2024 9:14:37

I am happy to announce that at the seminar in set theory and topology (on Tuesday 18.06.2024 at 17:15 in room A.4.1 C-19 (Wrocław University of Science and Technology) the lecture:

"The splitting ideal"

will be presented by

Aleksander Cieślak

Abstract:

We will investigate the cardinal invariants and the Katetov position of certain ideal on \omega. As a result we will obtain a new upper boundary of the covering number of the density zero ideal.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You

Szymon Żeberski

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

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

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

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

Wednesday seminar

Prague Set Theory Seminar

6/16/2024 17:21:28

Dear all, The seminar meets on Wednesday June 19th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Katerina Fukova -- Structure of semiartinian rings For (von Neumann) regular semiartinian rings with primitive factors artinian there is an invariant called dimension sequence (Theorem 2.1 in [1]) formed by slices of socle chain of the ring. The necessary conditions on this invariant were studied for example in [2]. We will focus on how much the dimension sequence determines the ring. I will discuss some specific case of commutative rings for which the ring corresponding to any suitable dimension sequence is (up to isomorphism) given by one construction from the ring of eventually constant sequences. Based on the joint work in progress with Jan Trlifaj. [1] P. Růžička, J. Trlifaj, J. Žemlička: Criteria of Steadiness. Marcel Dekker Abelian Groups, Module Theory, and Topology, 1998. [2] J. Žemlička: On socle chains of semiartinian rings with primitive factors artinian. Lobachevskii Journal of Mathematics, Volume 37, 2016, Pages 316-322. Best, David

KGRC talk June 20

Kurt Godel Research Center

6/14/2024 5:55:37

KGRC/Institute of Mathematics invites you to the following talk: Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, June 20, 11:30am--1:00pm, hybrid mode "Dense ideals (3/3) M. Eskew (U Wien) This is part of a three talk series. The first installment was on June 6 https://ucloud.univie.ac.at/index.php/s/f89ENYQLkdg4BNo, the second one on June 13 https://ucloud.univie.ac.at/index.php/s/HcbKs6J9LrdtKSD. In the third and final lecture of this series, we will finish outlining the proof of the consistency result that all $\aleph_n$ can simultaneously carry dense ideals. This will involve a "uniformization" forcing that follows the Shioya collapse, several strategic closure arguments, and lifting an almost-huge embedding. We will focus on the arguments for getting the result on $\aleph_1$ and $\aleph_2$, and briefly describe how to modify the uniformization forcing to go further. Zoom info: If you have not received the zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recordings available so far of the Set Theory Seminar: June 11: L. Notaro (U Turin, IT), "Computable vs. Descriptive Combinatorics of Local Problems" https://ucloud.univie.ac.at/index.php/s/s5D8KKtfrHASKeG June 13: M. Eskew (U Wien), "Dense ideals (2/3)" https://ucloud.univie.ac.at/index.php/s/HcbKs6J9LrdtKSD Video recordings available so far of the Logic Colloquium: June 13: P. Speissegger (McMaster U, Hamilton, CA), "How can model theory help understand Hilbert's 16th problem?" https://ucloud.univie.ac.at/index.php/s/7sdpoGbM3nWFe8o * * * * * * * * * Updates at https://kgrc.univie.ac.at/eventsnews/ -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16, #7.48 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

56th Nankai Logic Colloquium

Nankai Logic Colloquium

6/12/2024 11:08:33

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon.

Our speaker this week will be Lionel Nguyen Van The from Aix-Marseille University. This talk will take place this Friday, June 14th, from 4pm to 5pm (UTC+8, Beijing time).

Title: Ramsey theory in the context of Fraisse classes.

Abstract:
Structural Ramsey theory appeared naturally as a branch of Ramsey theory in the seventies, and is concerned with partition properties of combinatorial objects that are equipped with some structure (typically, in the sense of first order logic). While several seminal results were proved in those years, the subject was offered an unexpected revival thirty years later, whose consequences are still being felt today. This talk will be an attempt to describe the main lines of thought behind this story, starting from the pioneering work of Graham, Leeb, Nesetril, Rödl, Rothschild, Spencer and Voigt, continuing with that of Kechris, Pestov and Todorcevic, and finishing with that of Dobrinen.

________________________________________________________________________________________________

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

Title ：The 56th Nankai Logic Colloquium-- Lionel Nguyen Van The

Time ：16:00pm, Jun. 14, 2024(Beijing Time)

Zoom Number ： 436 658 8683

Passcode ：477893

Link ：https://frontai-hk.zoom.us/j/4366588683?pwd=ob0TsLuLeIl0JT7403RaqvFKgOnuRf.1&omn=86266820140

_____________________________________________________________________

Best wishes,

Ming Xiao

Set theory and topology seminar 11.06.2024 Jadwiga Świerczyńska

Wrocław Set Theory Seminar

6/8/2024 1:15:38

I am happy to announce that at the seminar in set theory and topology (on Tuesday 11.06.2024 at 17:15 in room A.4.1 C-19 (Wrocław University of Science and Technology) the lecture:

"On Q- and selective measures"

will be presented by

Jadwiga Świerczyńska

Abstract:

We will present some generalizations of well-known definitions of types of ultrafilters to the realm of finitely additive measures on $\omega$. We will show a few results similar to the ones for ultrafilters: measure is selective if and only if it is a P-measure and a Q-measure, and that selective measures (Q-measures, respectively) are minimal in the Rudin-Keisler (Rudin-Blass) ordering. We will also show an example of a selective non-atomic measure. The second part will be focused on the integration: we will briefly describe Lebesgue integral with respect to finitely additive measures on $\omega$ and prove that it is a generalization of an ultralimit. Finally, we will present an idea of further generalizations of these definitions for functionals on $\ell^{\infty}$.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You

Szymon Żeberski

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

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

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

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

KGRC talks June 11 -13

Kurt Godel Research Center

6/7/2024 5:49:00

KGRC/Institute of Mathematics invites you to the following talks: (updates at https://kgrc.univie.ac.at/eventsnews/ Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Tuesday, June 11, 3:00pm--4:30pm, hybrid mode "Does $\mathsf{DC}$ imply $\mathsf{AC_\omega}$, uniformly?" L. Notaro (U Turin, IT) The axiom of dependent choice $\mathsf{DC}$ and the axiom of countable choice $\mathsf{AC_\omega}$ are two weak forms of the axiom of choice that can be stated for a specific set: $\mathsf{DC}(X)$ assets that any total binary relation on $X$ has an infinite chain; $\mathsf{AC_\omega}(X)$ assets that any countable family of nonempty subsets of $X$ has a choice function. It is well-known that $\mathsf{DC}$ implies $\mathsf{AC_\omega}$. We discuss and sketch the proof of the following theorem: it is consistent with $\mathsf{ZF}$ that there is a set $A\subseteq \mathbb{R}$ such that $\mathsf{DC}(A)$ holds but $\mathsf{AC_\omega}(A)$ fails. This is joint work with Alessandro Andretta. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at Please direct any questions about this talk tovera.fischer@univie.ac.at. * * * * * * * * * Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, June 13, 11:30am--1:00pm, hybrid mode "Dense ideals (2/3) M. Eskew (U Wien) This is part of a three talk series. The first installment was on June 6 https://kgrc.univie.ac.at/eventsnews/event-details/news/dense-ideals-13/. In the second lecture, we will begin the consistency proof that all $\omega_n$ can carry dense ideals simultaneously. We start with preliminaries on complete $\kappa$-closure, continuous projections, and inverse limits. Then we introduce our main forcing, the Dual Shioya collapse, and establish its key properties. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recordings available so far of the Set Theory Seminar: June 6: M. Eskew (U Wien) "Dense ideals (1/3)" https://ucloud.univie.ac.at/index.php/s/f89ENYQLkdg4BNo -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16, #7.48 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

55th Nankai Logic Colloquium

Nankai Logic Colloquium

6/5/2024 23:00:24

Hello everyone,

This week our weekly Nankai Logic Colloquium will be in the afternoon.

Our speaker this week will be Rizos Sklinos from the Chinese Academy of Sciences. This talk will take place this Friday, June 7th, from 4pm to 5pm (UTC+8, Beijing time).

Title: First-order sentences in random groups

Abstract: Gromov in his seminal paper introducing hyperbolic groups claimed that a “typical” finitely presented group is hyperbolic. His statement can be made rigorous in various natural ways. The model of randomness that is preferentially focused on is Gromov's density model, as it allows a fair amount of flexibility. In this model a random group is hyperbolic with overwhelming probability. In a different line of thought, Tarski asked whether all non-abelian free groups share the same first-order theory (in the language of groups). This question proved very hard to tackle and only after more than 50 years Sela and Kharlampovich-Myasnikov answered the question positively. Combining the two, J. Knight conjectured that a first-order sentence holds with overwhelming probability in a random group if and only if it is true in a no abelian free group. In joint work with O. Kharlampovich we answer the question positively for universal-existential sentences.

___________________________________________________________________________________________________________________________________________________

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

Title ：The 55th Nankai Logic Colloquium-- Rizos Sklinos

Time ：16:00pm, Jun. 7, 2024(Beijing Time)

Zoom Number ： 436 658 8683

Passcode ：477893

Link ：https://frontai-hk.zoom.us/j/4366588683?pwd=ob0TsLuLeIl0JT7403RaqvFKgOnuRf.1&omn=85231005716

_____________________________________________________________________

Best wishes,

Ming Xiao

Wednesday seminar

Prague Set Theory Seminar

6/5/2024 10:54:02

Dear all, The seminar meets on Wednesday June 12th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Bryant Rosado Silva -- Generically hereditarily equivalent Peano continua We say that a continuum $X$ is hereditarily equivalent if every nondegenerate subcontinuum of it is homeomorphic to X. This concept is one of the main motivations behind the construction of the pseudo-arc. If considered in the hyperspace of continua of X, denoted by Cont(X), it means that Cont(X) \ Fin(X) = { K in Cont(X) : \ K ~ X }. This is an open and dense set, hence comeager, thus we can say that the generic subcontinua of X is homeomorphic to X. Therefore, it is natural to ask if there exist other spaces that satisfy this property of having such collection of homeomorphic sets comeager in the hyperspace. We call these spaces generically hereditarily equivalent continua and show that the generalized Wazewski dendrites W_M for M subset { 3,4,..., infinity } are examples. Moreover, in the hyperspace of maximal order arcs of W_M, the chains having every nondegenerate element homeomorphic to W_M make a comeager subset of the maximal order arcs. Finally, we show that it is possible to find a comeager collection of chains with even more specific properties. This is a joint work with Benjamin Vejnar (Charles University). Best, David

Cross-Alps Logic Seminar (speaker: Lorenz Halbeisen)

Cross-Alps Logic Seminar

6/3/2024 8:23:13

On Friday 07.06.2024 at 16.00 CEST

Lorenz Halbeisen (ETH Zürich)

will give a talk on

The Graph Embedding Property and its relation to the Prime Ideal

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

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

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

All the best,
Vincenzo

Wednesday seminar

Prague Set Theory Seminar

6/3/2024 6:14:37

Dear all, No seminar this Wednesday June 5th as many of the regular participants are not available. Best, David

Set theory and topology seminar 4.06.2024 Andres Uribe-Zapata (TU Wien)

Wrocław Set Theory Seminar

6/1/2024 15:49:49

I am happy to announce that at the seminar in set theory and topology (on Tuesday 4.06.2024 at 17:15 in room A.4.1 C-19 (Wrocław University of Science and Technology) the lecture:

"Finitely additive measures on Boolean algebras: freeness and integration"

will be presented by

Andres Uribe-Zapata (TU Wien)

Abstract:

In this talk, we present an integration theory with respect to finitely additive measures on a field of sets $\mathcal{B} \subseteq \mathcal(X)$ for some non-empty set $X$. For this, we start by reviewing some fundamental properties of finitely additive measures on Boolean algebras. Later, we present a definition of the integral in this context and some basic properties of the integral and the integrability. We also study integration over subsets of $X$ to introduce the Jordan algebra and compare the integration on this new algebra with the integration on $\mathcal{B}$. Finally, we say that a finitely additive measure on $\mathcal{B}$ is \emph{free} if $\mathcal{B}$ contains any finite subset of $X$ and its measure is zero. We close the talk by providing some characterizations of free finitely additive measures.

This is a joint work with Miguel A. Cardona and Diego A. Mejía.

References:

[CMU] Miguel A. Cardona, Diego A. Mejía and Andrés F. Uribe-Zapata. Finitely additive measures on Boolean algebras. In Preparation.

[UZ23] Andrés Uribe-Zapata. Iterated forcing with finitely additive measures: applications of probability to forcing theory. Master’s thesis, Universidad Nacional de Colombia, sede Medellín, 2023. https://shorturl.at/sHY59.

Feel free to spread this information among Your colleagues.

I'm looking forward to seeing You

Szymon Żeberski

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

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

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

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

KGRC Talk - June 6

Kurt Godel Research Center

5/31/2024 3:20:30

KGRC/Institute of Mathematics invites you to the following talk: Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, June 6, 11:30am--1:00pm, hybrid mode "Dense ideals (1/3)" M. Eskew (U Wien) In this three-part lecture series, I will present my recent result with Yair Hayut that it is consistent for all successors of regular cardinals to carry dense ideals. We will start a bit out of order with applications, beginning with Woodin’s "transfer theorem" that shows that if we have diamonds and a normal ideal $J$ on $\kappa^+$ such that $\mathcal{P}(\kappa^+)/J$ is equivalent to $\mathrm{Col}(\kappa$, \kappa^+$), then there is a uniform $\kappa$-complete ideal $K$ on $\kappa^+$ such that $\mathcal{P}(\kappa^+)/K$ is isomorphic to $\mathcal{P}(\kappa)/\mathrm{bounded}$. From this we can derive several combinatorial consequences that address some questions from graph theory and recent work on homological algebra on the ordinals. In the second and third lecture, we will outline the consistency proof. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * May, 23: V. Haberl (TU Wien); "Concentrated sets and γ-sets in the Miller model" https://ucloud.univie.ac.at/index.php/s/7GA9fX7MfSHXYYR Video recordings available so far of the Logic Colloquium: May, 23: P. Szewczak (Cardinal Stefan Wyszyński U, Warsaw, PL); "Centenary of the Menger Conjecture" https://ucloud.univie.ac.at/index.php/s/Zgt6x6sdTpHMq2o * * * * * * * * * Updates at https://kgrc.univie.ac.at/eventsnews/ -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16, #7.48 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

54th Nankai Logic Colloquium

Nankai Logic Colloquium

5/30/2024 1:23:14

Hello everyone,

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

Our speaker this week will be Andre Nies from the University of Auckland. This talk is going to take place this Friday, May 31, from 4pm to 5pm (UTC+8, Beijing time).

Title: Borel classes of closed subgroups of Sym(N)

Abstract: Closed subgroups of the permutation group Sym(N) are interesting, being the automorphism groups of models M with domain the natural numbers. We study various conjugation-invariant Borel classes from a logician’s point of view. The locally Roelcke precompact groups form the largest class considered. Interesting subclasses include the totally disconnected locally compact (t.d.l.c.) groups, and the oligomorphic group (when M is omega-categorical).

We establish for each class a Borel duality with a class of countable structures that are based on Roelcke precompact open cosets. This is used for an upper bound on the Borel complexity of topological isomorphism relations (with Schlicht and Tent), and for an algorithmic theory in the t.d.l.c. case (with Melnikov).

A lower bound on the complexity of topological isomorphism remains open for the oligomorphic groups. Paolini and Shelah obtained smoothness under the additional hypothesis that each open subgroup has the pointwise stabiliser of a finite set as a subgroup of finite index. Work in progress with Paolini establishes such an upper bound for several other subclasses, such as the case when the model M has no algebraicity.

___________________________________________________________________________________________________________________________________________________

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

Title ：The 54th Nankai Logic Colloquium-- Andre Nies

Time ：16:00pm, May. 31, 2024(Beijing Time)

Zoom Number ： 436 658 8683

Passcode ：477893

Link ：https://frontai-hk.zoom.us/j/4366588683?pwd=ob0TsLuLeIl0JT7403RaqvFKgOnuRf.1&omn=82728819387

_____________________________________________________________________

Best wishes,

Ming Xiao

Cross-Alps Logic Seminar (speaker: Mirna Džamonja)

Cross-Alps Logic Seminar

5/27/2024 14:35:15

On Friday 31.05.2024 at 16.00 CEST

Mirna Džamonja (CNRS-Université de Paris / IHPST)

will give a talk on

Transfer principles in logic

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

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

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

All the best,
Vincenzo

Wednesday seminar

Prague Set Theory Seminar

5/27/2024 5:37:28

Dear all, The seminar meets on Wednesday May 29th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- Ultrafilters and large continuum The exact content of the talk has not yet been determined. However, for sure it will involve ultrafilters on the natural numbers, forcing and continuum bigger than omega_2. Best, David

This Week in Logic at CUNY

5/19/2024 22:30:00

This Week in Logic at CUNY:

- - - - Monday, May 20, 2024 - - - -

- - - - Tuesday, May 21, 2024 - - - -

- - - - Wednesday, May 22, 2024 - - - -

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

Speaker: Emilio Minichiello , The CUNY Graduate Center.

Date and Time: Wednesday May 22, 2024, 7:00 - 8:30 PM. IN PERSON TALK!

Title: Presenting Profunctors.

Abstract: In categorical database theory, profunctors are ubiquitous. For example, they are used to define schemas in the algebraic data model. However, they can also be used to query and migrate data. In this talk, we will discuss an interesting phenomenon that arises when trying to model profunctors in a computer. We will introduce two notions of profunctor presentations: the UnCurried and Curried presentations. They are modeled on thinking of profunctors as functors P: C^op x D -> Set and as functors P: C^op -> Set^D, respectively. Semantically of course, these are equivalent, but their syntactic properties are quite different. The UnCurried presentations are more intuitive and easier to work with, but they carry a fatal flaw: there does not exist a semantics-preserving composition operation of UnCurried presentations that also preserves finiteness. Therefore we introduce the Curried presentations and show that they remedy this flaw. In the process, we characterize which UnCurried Presentations can be made Curried, and discuss some applications. This talk will be based off of this recent preprint which is joint work with Gabriel Goren Roig and Joshua Meyers.

- - - - Thursday, May 23, 2024 - - - -

- - - - Friday, May 24, 2024 - - - -

Next Week in Logic at CUNY:

- - - - Monday, May 27, 2024 - - - -

- - - - Tuesday, May 28, 2024 - - - -

- - - - Wednesday, May 29, 2024 - - - -

- - - - Thursday, May 30, 2024 - - - -

- - - - Friday, May 31, 2024 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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KGRC Talks - May 24

Kurt Godel Research Center

5/17/2024 4:16:21

KGRC/Institute of Mathematics invites you to the following talks: Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, May 23, 11:30am--1:00pm, hybrid mode "Concentrated sets and $\gamma$-sets in the Miller model" V. Haberl (TU Wien) Bartoszyński and Halbeisen conjectured that in the Miller model there exists a concentrated set of reals of size $\mathfrak{c} = \omega_2$. Let us recall that a set $X\subseteq 2^\omega$ is concentrated if there exists a countable $Q\subseteq X$ such that $|X\setminus U|\leq \omega$ for every open set $U \subseteq 2^\omega$ with $Q\subseteq U$. In our talk we shall present the main ideas of the proof that this conjecture is false. Concentrated sets are canonical examples of Rothberger spaces of reals. We want to analyse the possible cardinalities of sets of reals satisfying selection principles in the Miller model. To avoid triviality we are interested in the totally imperfect cases, i.e. spaces that do not contain a copy of the Cantor space. Note that since $\mathfrak{d}$-concentrated sets are totally imperfect Menger spaces, there are such spaces of size continuum (since $\mathfrak{d} = \mathfrak{c}$). We shall sketch the proof that for the strongest selection principle, the $\gamma$-set property, only cardinality atmost $\omega_1$ is possible. We hope that the tools of our results can be used as a prototype for the non-existence of Rothberger sets of reals with cardinality $\mathfrak{c}$. The goal would be to prove the same for Hurewicz totally imperfect sets of reals, the latter being a weaker property than Rothberger in the Miller model. The talk will be based on a recent joint work with Piotr Szewczak and Lyubomyr Zdomskyy. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Logic Colloquium Oskar-Morgenstern-Platz 1, 1090, 2nd floor, HS 11, Thursday, May 23, 3:00pm--3:50pm, hybrid mode "Centenary of the Menger Conjecture" P. Szewczak (Cardinal Stefan Wyszyński University, Warsaw, PL) In 1924, Menger observed that any metric space $X$ which is \emph{$\sigma$-compact} (i.e., it is a countable union of its compact subsets) has such a property that for any basis $\mathcal{B}$ of $X$, there are sets $B_0,B_1,\ldots\in\mathcal{B}$, such that $\mathrm{lim}_{n\to\infty}\mathrm{diam}(B_n)=0$ and $X=\bigcup_{n\in \omega }B_n$. Menger conjectured that the above property characterizes $\sigma$-compactness in the class of metric spaces. Soon thereafter Hurewicz reformulated the Menger property without using a metric: for any sequence $\mathcal{U}_0,\mathcal{U}_1,\ldots$ of open covers of a given topological space, there are finite sets $\mathcal{F}_1\subseteq\mathcal{U}_0, \mathcal{F}_1\subseteq\mathcal{U}_1,\ldots$ such that the family $\bigcup_{n\in\omega}\mathcal{F}_n$ is an open cover of the space.In that way, the definition of the Menger property was extended on all topological spaces. By the results of Fremlin--Miller and Bartoszyński--Tsaban, there is in ZFC a subspace of the real line which is Menger but no $\sigma$-compact. The aim of the talk is to present an overview of the Menger property which is one of the most influential property in the topological selections theory and it has many connections to topology, set-theory and function spaces. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at. Please direct any questions about this talk to matthias.aschenbrenner@univie.ac.at. * * * * * * * * * Video recordings available so far of the Set Theory Seminar: May, 14: O. Zindulka (Czech Technical U, Prague, CZ) "Combinatorics of Uniform Covers" https://ucloud.univie.ac.at/index.php/s/2BBqLQZy7TownbM May, 16: C.B. Switzer (U Wien) "Baumgartner's Axiom and Cardinal Characteristics: A Sparse Look at Dense Sets of Reals III" https://ucloud.univie.ac.at/index.php/s/BtQZfJS54fSnTJM Video recordings available so far of the Logic Colloquium: May, 16: R. Sklinos (Chinese Academy of Sciences, Beijing, CN) "First-order sentences in random groups" https://ucloud.univie.ac.at/index.php/s/59BbzjWPdGiCB8x * * * * * * * * * Updates at https://kgrc.univie.ac.at/eventsnews/. -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16, #7.48 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

Wednesday seminar

Prague Set Theory Seminar

5/16/2024 4:21:35

Dear all, The seminar meets on Wednesday May 22nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Next week there will also be an extra session of the Set Theory and Analysis seminar on Friday May 24th at 14:00, talk delivered by John Truss. (As well as an interesting talk on Tuesday morning.) See here: https://www.math.cas.cz/index.php/events/seminar/6 Program (Wednesday): Jindřich Zapletal -- Partition properties of omega one without choice I will show that certain natural partition properties of omega one which follow from the axiom of determinacy still hold in balanced extensions of the Solovay model, making them consistent with such objects as Vitali sets or ultrafilters. Best, David

53rd Nankai Logic Colloquium

Nankai Logic Colloquium

5/16/2024 0:21:51

Hello everyone,

This week our weekly Nankai Logic Colloquium is going to be in the afternoon, but at an irregular time, as we have two speakers this week.

Our speakers this week will be Yang Zheng and Ruiwen Li, both from Nankai University. This talk is going to take place this Friday, May 17th, from 2:30 pm to 5 pm (UTC+8, Beijing time). The first talk is starting at 2:30pm, and the second talk is starting at 4pm. Both talks are offline/online hybrid.

Yang Zheng:

Title: On equivalence relations induced by Polish groups

Abstract: In this talk, we introduce Borel orbit equivalence relations, denoted by E(G), which can well-describe the structures and properties of a Polish group G from the perspective of Borel reduction.

Given a Polish group G, let E(G) be the right coset equivalence relation $G^\omega/c(G)$, where c(G) is the group of all convergent sequences in G. We shall present the following results: for a non-trivial Polish group G, we have that: (1) G is a countable group iff $E(G)\sim_B E_0$; (2) G is TSI non-archimedean uncountable iff $E(G)\sim_B E^\omega_0$; and (3) G is non-archimedean iff $E(G)\leq_B =^+$. In particular, $E(S_\infty)\sim_B =^+$ holds. Moreover, we will provide some Rigid Theorems and a Pre-rigid Theorem on TSI Polish groups, which can transform the existence problem of Borel reduction between E(G) equivalence relations, into the existence problem of well-behaved continuous homomorphisms between Polish groups. This is a joint work with Longyun Ding.

Ruiwen Li:

Title: Topological Type and Conjugacy Relation on Minimal Systems

Abstract: The complexity of conjugacy relation on minimal systems under Borel reducibility is a well-known question in descriptive set theory. In this talk, by analyzing the conjugacy relation on Oxtoby systems, I'll define an equivalence relation named topological type, this relation gives a lower bound of conjugacy complexity of minimal systems and shows that the conjugacy relation on minimal systems cannot be classified by countable structures. Moreover, when considering the isomorphism relation of pointed minimal systems, the topological type relation describes its exact complexity.

__________________________________________________________________________________________________________________________

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

Title ：The 53th Nankai Logic Colloquium

Time ：14:30pm, May. 17, 2024(Beijing Time)

Zoom Number ： 371 037 9317

Passcode ：477893

Link ：https://zoom.us/j/3710379317?pwd=WEpLTjBtV1B2SHZaaFpnWU1qNzJVQT09&omn=92298090494

_____________________________________________________________________

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

Best wishes,

Ming Xiao

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY

5/13/2024 10:25:31

Hi everyone,

Note the addition of two talks in the NYC Category Theory Seminar, May 15 and May 22.

Best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, May 13, 2024 - - - -

- - - - Tuesday, May 14, 2024 - - - -

Computational Logic Seminar

Spring 2024 (online)
Tuesday, May 14, Time 2:00 - 4:00 PM (EDT)
zoom link: ask Sergei Artemov sartemov@gmail.com

Speaker: Hans van Ditmarsch, CNRS, IRIT, University of Toulouse, France

Title: Epistemic logic and simplicial complexes

Abstract: All my working life as a logician epistemic logic came with Kripke models, in particular the kind for multiple agents with equivalence relations to interpret knowledge. Sure enough, I knew about enriched Kripke models, like subset spaces, or with topologies. But at some level of abstraction you get back your standard Kripke model. Imagine my surprise, around 2018, that there is an entirely dual sort of structure on which the epistemic logical language can be interpreted and that results in the same S5 logic: simplicial complexes. Instead of points that are worlds and links labeled with agents, we now have points that are agents and links labeled with worlds. Or, instead of edges (links), triangles, tetrahedrons, etcetera, that represent worlds. Simplicial complexes are well-known within combinatorial topology and have wide usage in distributed systems to model (a)synchronous computation. The link with epistemic modal logic is recent, spreading out from Mexico City and Paris to other parts of the world, like Vienna and Bern. Other logics are relevant too, for example KB4, in order to encode crashed processes/agents. Other epistemics are relevant too, and in particular distributed knowledge, which facilitates further generalizations from simplicial complexes to simplicial sets. It will be my pleasure to present my infatuation with this novel development connecting epistemic logic and distributed computing. Suggested introductory reading is:

https://arxiv.org/abs/2002.08863
https://link.springer.com/chapter/10.1007/978-3-030-75267-5_1
Knowledge and Simplicial Complexes
Hans van Ditmarsch, Eric Goubault, Jeremy Ledent, Sergio Rajsbaum

https://drops.dagstuhl.de/entities/document/10.4230/DagRep.13.7.34
Epistemic and Topological Reasoning in Distributed Systems (Dagstuhl Seminar 23272)
Armando Castañeda, Hans van Ditmarsch, Roman Kuznets, Yoram Moses, Ulrich Schmid
Section 4.3 Representing Epistemic Attitudes via Simplicial Complexes

- - - - Wednesday, May 15, 2024 - - - -

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

Speaker: Raymond Puzio.

Date and Time: Wednesday May 15, 2024, 7:00 - 8:30 PM. IN-PERSON!

Title: Uniqueness of Classical Retrodiction.

Abstract: In previous talks at this Category seminar and at the Topology, Geometry and Physics seminar, Arthur Parzygnat showed how Bayesian inversion and its generalization to quantum mechanics may be interpreted as a functor on a suitable category of states which satisfies certain axioms. Such a functor is called a retrodiction and Parzygnat and collaborators conjectured that retrodiction is unique. In this talk, I will present a proof of this conjecture for the special case of classical probability theory on finite state spaces.

In this special case, the category in question has non-degenerate probability distributions on finite sets as its objects and stochastic matrices as its morphisms. After preliminary definitions and lemmas, the proof proceeds in three main steps.

In the first step, we focus on certain groups of automorphisms of certain objects. As a consequence of the axioms, it follows that these groups are preserved under any retrodiction functor and that the restriction of the functor to such a group is a certain kind of group automorphism. Since this group is isomorphic to a Lie group, it is easy to prove that the restriction of a retrodiction to such a group must equal Bayesian inversion if we assume continuity. If we do not make that assumption, we need to work harder and derive continuity "from scratch" starting from the positivity condition in the definition of stochastic matrix.

In the second step, we broaden our attention to the full automorphism groups of objects of our category corresponding to uniform distributions. We show that these groups are generated by the union of the subgroup consisting of permutation matrices and the subgroup considered in the first step. From this fact, it follows that the restriction of a retrodiction to this larger group must equal Bayesian inversion.

In the third step, we finally consider all the objects and morphisms of our category. As a consequence of what we have shown in the first two steps and some preliminary lemmas, it follows that retrodiction is given by matrix conjugation. Furthermore, Bayesian inversion is the special case where the conjugating matrices are diagonal matrices. Because the hom sets of our category are convex polytopes and a retrodiction functor is a continuous bijection of such sets, a retodiction must map polytope faces to faces. By an algebraic argument, this fact implies that the conjugating matrices are diagonal, answering the conjecture in the affirmative.

Paper.

- - - - Thursday, May 16, 2024 - - - -

*** FINAL EXAMS WEEK BEGINS - CUNY GRADUATE CENTER ***

- - - - Friday, May 17, 2024 - - - -

Next Week in Logic at CUNY:

- - - - Monday, May 20, 2024 - - - -

- - - - Tuesday, May 21, 2024 - - - -

- - - - Wednesday, May 22, 2024 - - - -

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

Speaker: Emilio Minichiello , The CUNY Graduate Center.

Date and Time: Wednesday May 22, 2024, 7:00 - 8:30 PM. IN PERSON TALK!

Title: Presenting Profunctors.

Abstract: In categorical database theory, profunctors are ubiquitous. For example, they are used to define schemas in the algebraic data model. However, they can also be used to query and migrate data. In this talk, we will discuss an interesting phenomenon that arises when trying to model profunctors in a computer. We will introduce two notions of profunctor presentations: the UnCurried and Curried presentations. They are modeled on thinking of profunctors as functors P: C^op x D -> Set and as functors P: C^op -> Set^D, respectively. Semantically of course, these are equivalent, but their syntactic properties are quite different. The UnCurried presentations are more intuitive and easier to work with, but they carry a fatal flaw: there does not exist a semantics-preserving composition operation of UnCurried presentations that also preserves finiteness. Therefore we introduce the Curried presentations and show that they remedy this flaw. In the process, we characterize which UnCurried Presentations can be made Curried, and discuss some applications. This talk will be based off of this recent preprint which is joint work with Gabriel Goren Roig and Joshua Meyers.

- - - - Thursday, May 23, 2024 - - - -

- - - - Friday, May 24, 2024 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

This Week in Logic at CUNY

5/12/2024 22:31:00

Hi everyone,

This will be our last edition of "This Week in Logic at CUNY" for the Spring 2024 semester -- regular mailings will resume in late August. Special updates may be sent for events that arise in the meantime.

Wishing you a happy and productive summer!

All the best,

Jonas

This Week in Logic at CUNY:

- - - - Monday, May 13, 2024 - - - -

- - - - Tuesday, May 14, 2024 - - - -

Computational Logic Seminar

Spring 2024 (online)
Tuesday, May 14, Time 2:00 - 4:00 PM (EDT)
zoom link: ask Sergei Artemov sartemov@gmail.com

Speaker: Hans van Ditmarsch, CNRS, IRIT, University of Toulouse, France

Title: Epistemic logic and simplicial complexes

Abstract: All my working life as a logician epistemic logic came with Kripke models, in particular the kind for multiple agents with equivalence relations to interpret knowledge. Sure enough, I knew about enriched Kripke models, like subset spaces, or with topologies. But at some level of abstraction you get back your standard Kripke model. Imagine my surprise, around 2018, that there is an entirely dual sort of structure on which the epistemic logical language can be interpreted and that results in the same S5 logic: simplicial complexes. Instead of points that are worlds and links labeled with agents, we now have points that are agents and links labeled with worlds. Or, instead of edges (links), triangles, tetrahedrons, etcetera, that represent worlds. Simplicial complexes are well-known within combinatorial topology and have wide usage in distributed systems to model (a)synchronous computation. The link with epistemic modal logic is recent, spreading out from Mexico City and Paris to other parts of the world, like Vienna and Bern. Other logics are relevant too, for example KB4, in order to encode crashed processes/agents. Other epistemics are relevant too, and in particular distributed knowledge, which facilitates further generalizations from simplicial complexes to simplicial sets. It will be my pleasure to present my infatuation with this novel development connecting epistemic logic and distributed computing. Suggested introductory reading is:

https://arxiv.org/abs/2002.08863
https://link.springer.com/chapter/10.1007/978-3-030-75267-5_1
Knowledge and Simplicial Complexes
Hans van Ditmarsch, Eric Goubault, Jeremy Ledent, Sergio Rajsbaum

https://drops.dagstuhl.de/entities/document/10.4230/DagRep.13.7.34
Epistemic and Topological Reasoning in Distributed Systems (Dagstuhl Seminar 23272)
Armando Castañeda, Hans van Ditmarsch, Roman Kuznets, Yoram Moses, Ulrich Schmid
Section 4.3 Representing Epistemic Attitudes via Simplicial Complexes

- - - - Wednesday, May 15, 2024 - - - -

- - - - Thursday, May 16, 2024 - - - -

*** FINAL EXAMS WEEK BEGINS - CUNY GRADUATE CENTER ***

- - - - Friday, May 17, 2024 - - - -

Next Week in Logic at CUNY:

- - - - Monday, May 20, 2024 - - - -

- - - - Tuesday, May 21, 2024 - - - -

- - - - Wednesday, May 22, 2024 - - - -

- - - - Thursday, May 23, 2024 - - - -

- - - - Friday, May 24, 2024 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

120 Years of Choice, Leeds, 8–12 July 2024

Conference

5/12/2024 1:00:00

120 Years of Choice, 8–12 July, 2024 This is a reminder for our conference 120 Years of Choice that will take place at the University of Leeds from 8th to 12th of July. For those that are still undecided, the scope of the conference is not limited to the Axiom of Choice and we will have a wide variety of speakers coming from different areas. The same of course also applies to poster submissions. Registration is still open until June 20th (20/06/2024), but we would like to ask all participants to register at their earliest convenience, so that we can plan accordingly. We have now extended the submission deadline for posters to May 31st (31/05/2024). Let us reiterate that we may be able to offer some financial support to those presenting a poster. We encourage any early career researchers to apply. For registration see more details at https://120ac.set-theory.info or email us at 120ac@leeds.ac.uk.

Link to more info

Tagged: Assaf Rinot, Assaf Shani, Azul Fatalini, David Asperó, Diana Montoya, Inbar Oren, John Steel, Kameryn WilliamsLorenzo Notaro, Martina Iannella, Moti Gitik, Natasha Dobrinen, Sheila Miller Edwards, Siiri Kivimäki, Toshimichi Usuba, Yair Hayut, Philipp Schlicht

Set Theory in the United Kingdom, Oxford, 16 May 2024

Conference

5/12/2024 0:00:00

STUK 13 ("Set Theory in the United Kingdom") will take place at the Mathematical Institute of the University of Oxford on Thursday, 16 May 2024. We have already secured István Juhász and Thilo Weinert as invited speakers who both plan to be there in person. https://www.dpmms.cam.ac.uk/~dbl25/STUK/ The schedule will be roughly as for the past meetings: we start in the late morning, have one talk before lunch, then lunch, then two more talks, and then ample time for "informal presentations" where everyone can and should speak to present themselves, their open questions, their research project, or their results.

Link to more info

Tagged: István Juhász, Julia Millhouse, Thilo Weinert

Wednesday seminar

Prague Set Theory Seminar

5/11/2024 3:07:29

Dear all, The seminar meets on Wednesday May 15th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- Basically generated ultrafilters This is a continuation of the last talk. We will recall and extend some facts that were already presented. Then we will prove some results on the existence of basically generated ultrafilters. Best, David

KGRC Set Theory Talks - May 12-17

Kurt Godel Research Center

5/8/2024 12:17:52

KGRC/Institute of Mathematics invites you to the following talks: SetTheory Seminar Kolingasse 14–16, 1090, 1st floor, SR 10, hybrid mode TUESDAY, May 14, 3:00pm–4:30pm ”Combinatorics of Uniform Covers” O. Zindulka (Czech Technological University, Prague, CZ) We look at diagonalization properties for sequences of various flavors of uniform covers of separable metric spaces and we describe them with game-theoretic and Ramsey-like partition properties. Applications include strong measure zero, null-additive and meager-additive sets in Polish groups, Menger-bounded spaces etc. Some highlights: a link to fractal measures and how it can help with calculation of cardinal invariants; Galvin-Mycielski-Solovay Theorem in various contexts;a solution to a Scheepers problem regarding products of strong measure zero spaces. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Set Theory Seminar Kolingasse 14--16, 1090, 1st floor, SR 10, Thursday, May 16, 11:30am--1:00pm, hybrid mode "Baumgartner's Axiom and Cardinal Characteristics: A Sparse Look at Dense Sets of Reals III" C. B. Switzer (U Wien) Mini-course (25.04.2024-16.05.2024, 3 lectures) - 3rd lecture: Given a cardinal $\kappa$, a set of reals $A\subseteq \mathbb R$ is $\kappa$-dense if its intersection with any open interval has size $\kappa$. Baumgartner's axiom (BA)---proved consistent by Baumgartner in 1973---states that all $\aleph_1$-dense sets of reals are order isomorphic with the induced linear order from $\mathbb R$. This is the most straightforward generalization to the uncountable of Cantor's proof that all countable dense linear orders without endpoints are order isomorphic. BA has variations to other topological spaces---given a topological space $X$, a subset $A \subseteq X$ is $\kappa$-dense if its intersection with each non-empty open subset has size $\kappa$. The axiom BA($X$) states that given any two $\aleph_1$-dense subsets of $X$, say $A$ and $B$, there is an autohomeomorphism of $X$ mapping $A$ onto $B$. In this parlance BA is equivalent to BA ($\mathbb R$). Surprisingly BA is not equivalent to BA ($\mathbb R^n$) for any finite $1< n < \omega$. In fact BA does not follow from Martin's Axiom (Abraham-Rubin-Shelah) though BA($\mathbb R^n$) does (in fact from $\mathfrak{p} > \aleph_1$) for each $n > 1$ (Steprāns-Watson). In these three lectures I will discuss these ideas and some related ones including the question of when BA($X$) implies BA($Y$) for Polish spaces $X$ and $Y$. Central to these questions are the role of cardinal characteristics including the celebrated theorem of Todorčević that BA implies $\mathfrak b > \aleph_1$ as well as a recent, higher dimensional analogue of this result that for any $n < \omega$ BA($\mathbb R^n$) implies $\mathfrak b > \aleph_1$ (S.-Steprāns). There are many beautiful open problems in this area and I plan to make discussing them a focal point of the talks. The talks will start slowly and should be accessible to students. Time permitting, the final talk will include some new results. If and when these results are presented, they are joint work with Juris Steprāns. Zoom info: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at Please direct any questions about this talk to vera.fischer@univie.ac.at. * * * * * * * * * Video recordings available of the Set Theory Workshop ”Compactness and Cardinal Invariants, Vienna, May 3, 2024: C. Agostini (TU Wien), "On Nagata-Smirnov spaces and metrizability-like properties" https://ucloud.univie.ac.at/index.php/s/DpQiNFzdqxpptfT S. Bardyla (U Wien), "Bohr compactification of discrete groups and Schur ultrafilters" https://ucloud.univie.ac.at/index.php/s/3cpFpjNMZ6z5ejG J. Cancino (Czech Academy of Sciences, Prague, CZ), "Some results on Tukey types of ultrafilters on the natural numbers" https://ucloud.univie.ac.at/index.php/s/8eiGqEsGCszYEG6 M. Iannella (TU Wien), "Descriptive consequences of rank-into-rank axioms" https://ucloud.univie.ac.at/index.php/s/rSjEQYjTzbdE6os Ch. Lambie-Hanson (Czech Academy of Sciences, Prague, CZ), "Hajnal-Máté graphs and club guessing" https://ucloud.univie.ac.at/index.php/s/pzpofnbPMyJZ9WY A. Medini (TU Wien), "A complete classification of the zero-dimensional homogeneous spaces under determinacy" https://ucloud.univie.ac.at/index.php/s/QfZ8ccqaKk5anwH J.M. Millhouse (U Wien), "Projectively definable mad families of multiple sizes" https://ucloud.univie.ac.at/index.php/s/kGPsfCgqJBQPKPk Š. Stejskalová (Charles U, Prague, CZ), "Forcing over a free Suslin tree" https://ucloud.univie.ac.at/index.php/s/HTpXbwd9cd5zcRJ C.B. Switzer (U Wien), "Baumgartner’s axiom and its higher dimensional versions" https://ucloud.univie.ac.at/index.php/s/224KHG2b9nJgp3w T. van der Vlugt (TU Wien), "The horizontal direction" https://ucloud.univie.ac.at/index.php/s/nSGmaJNbzpoHAoN * * * * * * * * * Updates at https://kgrc.univie.ac.at/eventsnews/) -- Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16, #7.48 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501

This Week in Logic at CUNY

5/5/2024 22:07:18

This Week in Logic at CUNY:

- - - - Monday, May 6, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 6, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395

Lorenzo Rossi (Turin)
Title: Alethic pluralism and Kripkean truth

Abstract: According to alethic pluralism, there is more than one way of being true: truth is not unique, in that there is a plurality of truth properties each of which pertains to a specific domain of discourse. This paper shows how such a plurality can be represented in a coherent formal framework by means of a Kripke-style construction that yields intuitively correct extensions for distinct truth predicates. The theory of truth it develops can handle at least three crucial problems that have been raised in connection with alethic pluralism: mixed compounds, mixed inferences, and semantic paradoxes.

Note: This is joint work with Andrea Iacona (Turin) and Stefano Romeo (Turin).

- - - - Tuesday, May 7, 2024 - - - -

MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)

Tuesday, May 7, 1pm

Ali Enayat, University of Gothenburg
Tarski's undefinability of truth theorem strikes again

Tarski's undefinability of truth theorem has two versions, the first one deals with truth itself, takes some effort to prove, and is a descendant of the Epimenides (liar) paradox. The second one deals with the related concept of satisfaction, has a one-line proof, and is a descendent of Russell's paradox. This talk is about the first one, which appeared in the 1953 monograph 'Undecidable Theories' by Tarski, Mostowski, and Robinson; it was employed there to show the essential undecidability of consistent theories that can represent all recursive functions (a strong form of the Gödel-Rosser incompleteness theorem). I will present Tarski's original 1953 formulation (which differs from the common formulation in modern expositions) and will explain how it was used in my recent work with Albert Visser to show that no consistent completion of a sequential theory whose signature is finite is axiomatizable by a collection of sentences of bounded quantifier-alternation-depth. A variant of this result was proved independently by Emil Jeřábek, as I will explain. Our proof method has a pedagogical dividend since it allows one to replace the cryptic Gödel-Carnap fixed point lemma with the perspicuous undefinability of truth theorem in the proof of the Gödel-Rosser incompleteness theorem.

Computational Logic Seminar

Spring 2024 (online)
Tuesday, May 7, Time 2:00 - 4:00 PM (EDT)
zoom link: ask Sergei Artemov sartemov@gmail.com
Speaker: SREEHARI KALLOORMANA, Graduate Center CUNY
Title: Formal Argumentation Theory and Argumentation Logics.

Abstract: Deductive Logic is monotonic, in that when the set of premises grows, the set of conclusions grows as well. Since the 1980s, Non-monotonic Logics, where this does not hold, have been studied to model commonsense reasoning, especially in the field of artificial intelligence. In this talk, we will be looking at argument-based nonmonotonic logics, which formalize the notion of attack and defeat in the field of argumentation theory. We will consider briefly abstract argumentation frameworks and the various semantic notions proposed by P.M. Dung in 1995, followed by logic-based structured argumentation frameworks `a la John Pollock, and the more recent ASPIC framework. Various notions of argument attack/defeat fundamental to argumentation, such as rebuttal, undercutting, and undermining, will be discussed. We will then introduce and discuss the idea of reasoning about argumentation using Justification logic, by introducing priority orderings over formulas and justification terms.

- - - - Wednesday, May 8, 2024 - - - -

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

Speaker: Juan Orendain, Case Western Univeristy.

Date and Time: Wednesday May 8, 2024, 7:00 - 8:30 PM. ZOOM TALK.

Title: Canonical squares in fully faithful and absolutely dense equipments.

Abstract: Equipments are categorical structures of dimension 2 having two separate types of 1-arrows -vertical and horizontal- and supporting restriction and extension of horizontal arrows along vertical ones. Equipments were defined by Wood in [W] as 2-functors satisfying certain conditions, but can also be understood as double categories satisfying a fibrancy condition as in [Sh]. In the zoo of 2-dimensional categorical structures, equipments nicely fit in between 2-categories and double categories, and are generally considered as the 2-dimensional categorical structures where synthetic category theory is done, and in some cases, where monoidal bicategories are more naturally defined.

In a previous talk in the seminar, I discussed the problem of lifting a 2-category into a double category along a given category of vertical arrows, and how this problem allows us to define a notion of length on double categories. The length of a double category is a number that roughly measures the amount of work one needs to do to reconstruct the double category from a bicategory along its set of vertical arrows.

In this talk I will review the length of double categories, and I will discuss two recent developments in the theory: In the paper [OM] a method for constructing different double categories from a given bicategory is presented. I will explain how this construction works. One of the main ingredients of the construction are so-called canonical squares. In the preprint [O] it is proven that in certain classes of equipments -fully faithful and absolutely dense- every square that can be canonical is indeed canonical. I will explain how from this, it can be concluded that fully faithful and absolutely dense equipments are of length 1, and so they can be 'easily' reconstructed from their horizontal bicategories.

References:
[O] Length of fully faithful framed bicategories. arXiv:2402.16296.
[OM] J. Orendain, R. Maldonado-Herrera, Internalizations of decorated bicategories via π-indexings. To appear in Applied Categorical Structures. arXiv:2310.18673.
[W] R. K. Wood, Abstract Proarrows I, Cahiers de topologie et géométrie différentielle 23 3 (1982) 279-290.
[Sh] M. Shulman, Framed bicategories and monoidal fibrations. Theory and Applications of Categories, Vol. 20, No. 18, 2008, pp. 650–738.

- - - - Thursday, May 9, 2024 - - - -

- - - - Friday, May 10, 2024 - - - -

Model Theory Seminar
CUNY Graduate Center
Friday May 10, 12:30pm NY time, Room: 6495

Alf Dolich, CUNY
The decidability of the rings Z/mZ

In this expository talk I will discuss recent work of Derakhshan and Macintyre on the decidability of the common theory of the rings Z/mZ as m varies through the natural numbers m>1.

Logic Workshop
CUNY Graduate Center
Friday May 10, 2:00pm-3:30pm, Room 5417

Roman Kossak, CUNY
The lattice problem for models of arithmetic

The lattice problem for models of PA is to determine which lattices can be represented either as lattices of elementary substructures of a model of PA or, more generally, which can be represented as lattices of elementary substructures of a model N that contain a given elementary substructure M of N.

Since the 1970's, the problem generated much research with highly nontrivial results with proofs combining specific methods in the model theory of arithmetic with lattice theory and various combinatorial theorems. The problem has a definite answer in the case of distributive lattices, and, despite much effort, there are still many open questions in the nondistributive case. I will briefly survey some early results and present a few proofs that illustrate the difference between the distributive and nondistributive cases.

Next Week in Logic at CUNY:

- - - - Monday, May 13, 2024 - - - -

- - - - Tuesday, May 14, 2024 - - - -

- - - - Wednesday, May 15, 2024 - - - -

- - - - Thursday, May 16, 2024 - - - -

*** FINAL EXAMS WEEK BEGINS - CUNY GRADUATE CENTER ***

- - - - Friday, May 17, 2024 - - - -

- - - - Other Logic News - - - -

- - - - Web Site - - - -

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

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

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Logic Seminar 8 May 2024 17:00 hrs at NUS

NUS Logic Seminar

5/3/2024 2:34:26

Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 08 May 2024, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-04 Speaker: Vittorio Cipriano Title: Characterizing different notions of learnability of structures URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html In this talk, we combine computable structure theory and inductive inference to study learning of families of structures. All the structures we consider are relational and countable and all the families of structures we consider are at most countable. The framework we use was defined in a series of papers by Bazhenov, Fokina, Koetzing and San Mauro. In a nutshell, the framework models the scenario in which, given a family of structures K, a learner receives more and more information about the atomic diagram of a copy of some A in K and, at each stage, is required to output a conjecture about the isomorphism type of such a structure. In this context, a natural criterion to consider is Ex-learning in which we require the learner to stabilize to the correct conjecture after finitely many steps. Together with Bazhenov and San Mauro we gave a descriptive set-theoretic characterization of Ex-learning. Namely, we showed that a family of structures is Ex-learnable if and only if the corresponding isomorphism problem continuously reduces to E_0, the equivalence relation of eventual agreement on infinite binary sequences. Replacing E_0 with other equivalence relations, one obtains a hierarchy to rank such isomorphism problems. That is, a family of structures K is E-learnable, for an equivalence relation E, if there is a continuous reduction from the isomorphism problem associated with K to E. We aim to obtain model-theoretic characterization of E-learning for different equivalence relations E. Some characterizations are already present in the literature: here we show that a family of structures K such that for any A_i, A_j in K there is a Sigma_n^{inf} formula satisfied by A_i but not by A_j is E-learnable if and only if E is the (iteration of the) Friedman-Stanely jump of the identity either on natural numbers or on Cantor space. We also show that other learning criteria coming from the classical setting of inductive inference of formal languages or recursive functions have a nice model-theoretic characterization. This talk collects joint works with Bazhenov, Jain, Marcone, San Mauro and Stephan.

Fwd: 9 FMP: przestrzenie Banacha: geometria i operatory

Wrocław Set Theory Seminar

5/1/2024 3:26:46

---------- Forwarded message ---------
Od: Grzegorz Plebanek <grzegorz.plebanek@math.uni.wroc.pl>
Date: wt., 30 kwi 2024 o 22:47
Subject: Fwd: 9 FMP: przestrzenie Banacha: geometria i operatory
To: Szymon Żeberski <szymon.zeberski@pwr.edu.pl>
Cc: <sebastian.jachimek@math.uni.wroc.pl>, Piotr Borodulin-Nadzieja <pborod@math.uni.wroc.pl>

Szymonie, rozeslij to, proszę do wszystkich z seminarium. To Jest wiadomość od Tomka Kanii (który prosi o informowanie wszystkich zainteresowanych) w sprawie sesji Przestrzenie Banacha, ale na liście konferencji jest też sesja Teoria Mnogości. Pozdrawiam, G

---------- Forwarded message ---------
Od: Tomasz Kania <tomasz2.kania@uj.edu.pl>
Date: wt., 30 kwi 2024 o 21:10
Subject: 9 FMP: przestrzenie Banacha: geometria i operatory

okazuje się, że sesja z przestrzeni Banacha się odbędzie (nie jest jednak jeszcze jasne, którego dnia konferencji); jeżeli nadal wyrażasz zainteresowanie przyjazdem, bardzo proszę o przesłanie abstraktu na:

Abstrakty - 9. Forum Matematyków Polskich (us.edu.pl)

(oraz idealnie potwierdzenie emailowe do mnie, że udało Ci się posłać).

Set Theory Workshop "Compactness and Cardinal Invariants" Vienna, May 2, 2024

Conference

5/3/2024

Set Theory Workshop at OMP and Kolingasse Together with our Czech research partners we invite you to this Workshop. Time and location: Morning session 9:00-12:00, Oskar-Morgenstern-Platz 1, SR 6, 1st fl. Afternoon session 14:00-17:55, Kolingasse 14-16, SR 1, 1st fl. Zoom info: Please contact petra.czarnecki@univie.ac.at Program: 09 : 00 − 9 : 30 Andrea Medini 09 : 35 − 10 : 05 Šárka Stejskalová 10 : 05 − 10 : 40 COFFEE 10 : 40 − 11 : 10 Corey Switzer 11 : 15 − 11 : 45 Serhii Bardyla 12 : 00 − 14 : 00 LUNCH 14 : 00 − 14 : 30 Chris Lambie-Hanson 14 : 35 − 15 : 05 Jonathan Cancino 15 : 05 − 15 : 40 COFFEE 15 : 40 − 16 : 10 Julia Millhouse 16 : 15 − 16 : 45 Tristan van der Vlugt 16 : 50 − 17 : 20 Martina Iannella 17 : 25 − 17 : 55 Claudio Agostini Organizer: Vera Fischer (U Wien) Radek Honzik (Charles University, Prague, CZ) If you have any questions, please write to the organizers. For more information see the program.

Link to more info

Tagged: Andrea Medini, Šárka Stejskalová, Corey Switzer, Serhii Bardyla, Chris Lambie-Hanson, Jonathan Cancino, Julia Millhous, Tristan van der Vlugt, Martina Iannella, Claudio Agostini

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY

4/29/2024 19:49:19

Hi everyone,

Note the addition of a talk by Benjamin Prudhomme in the Computational Logic Seminar on Tuesday 4/30.

All best,

Jonas

This Week in Logic at CUNY:

*** CUNY SPRING RECESS APRIL 22 - 30 ***

- - - - Monday, Apr 29, 2024 - - - -

Rutgers Logic Seminar
Monday Apr 29, 3:30pm Hill Center, Hill 705

Gabe Goldberg, Berkeley

Generalizations of the Ultrapower Axiom

Logic and Metaphysics Workshop
Date: Monday, April 29, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395

Anandi Hattiangadi (Stockholm).
Title: Physicalism, intentionality and normativity: The essential explanatory gap

Abstract: In this paper, I present an explanatory gap argument against the view that the semantic facts are fully grounded in the physical facts. Unlike traditional explanatory gap arguments, which stem from the failure of analytic reductive explanation, the explanatory gap I point to stems from the failure of metaphysical explanation. I argue for the following theses. (i) Physicalist grounding claims are metaphysically necessary, if true. (ii) To be explanatorily adequate, these grounding claims must be deducible from facts about essence. (iii) Semantico-physical grounding claims are possibly false, not (only) because they are conceivably false, but because they cannot be deduced from facts about essence. (iv) Semantic properties are essentially weakly normative: it lies in their natures to have correctness conditions and subjectively rationalize—rather than merely cause—behaviour. This gives rise to an explanatory gap that indicates that the semantic facts are not fully grounded in the physical facts.

- - - - Tuesday, Apr 30, 2024 - - - -

Computational Logic Seminar
Spring 2024 (online)
Tuesday, April 30
Time 2:00 - 4:00 PM (EDT)
zoom link: ask Sergei Artemov sartemov@gmail.com
Speaker: Benjamin PrudHomme, Graduate Center CUNY
Title: On Game Theory and Epistemic Logic

Abstract: Review of basic game theory and epistemic game theory concepts, including strictly competitive games, pure and mixed strategy Nash equilibria, rationalizability, models of knowledge, distinction between mutual and common knowledge. Review of proofs of when a game has a Nash equilibrium, Nash's Theorem, Muddy Children Problem. Discussions of current and potential future efforts to utilize logic in developing a more comprehensive theory of pure strategy solutions.

- - - - Wednesday, May 1, 2024 - - - -

- - - - Thursday, May 2, 2024 - - - -

- - - - Friday, May 3, 2024 - - - -

Model Theory Seminar
CUNY Graduate Center
Friday May 3, 12:30pm NY time, Room: 6495

Athar Abdul-Quader, Purchase College
Genericity in models of arithmetic

In this talk, I plan to explore a few notions of 'genericity' in the context of models of arithmetic. I will recall the notion of genericity borrowed from set-theory, used by Simpson to prove that every countable model of PA has an expansion to a pointwise definable model of PA*. I will then explore other notions of genericity inspired by more model-theoretic contexts. One such notion is 'neutrality': in a model M, we say an undefinable set X is neutral if the definable closure relation in (M, X) is the same as in M. Another notion, inspired by work done on model-theoretic genericity by Chatzidakis and Pillay, is called CP-genericity. I will explore these notions and outline some results, including: (1) every model of PA has a neutral set which is not CP-generic, (2) every countable model of PA has a CP-generic which is not neutral (and in fact, fails neutrality spectacularly: ie, we can find a CP-generic where the expansion is pointwise definable), and (3) every countable model of PA has a neutral CP-generic. This talk touches on work contained in two papers, one of which was joint work with Roman Kossak, and the other was joint work with James Schmerl.

Set Theory Seminar
CUNY Graduate Center
Friday, May 3, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.

Spencer Unger, University of Toronto
Iterated ultrapower methods in analysis of Prikry type forcing

We survey some old and new results in singular cardinal combinatorics whose proofs can be phrased in terms of iterated ultrapowers and ask a few questions.

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

Christian Wolf, CUNY
Computability of entropy and pressure on compact symbolic spaces beyond finite type

In this talk we discuss the computability of the entropy and topological pressure on compact shift spaces and continuous potentials . This question has recently been studied for subshifts of finite type (SFTs) and their factors (Sofic shifts). We develop a framework to address the computability of the entropy pressure on general shift spaces and apply this framework to coded shifts. In particular, we prove the computability of the topological pressure for all continuous potentials on S-gap shifts, generalized gap shifts, and Beta shifts. We also construct shift spaces which, depending on the potential, exhibit computability and non-computability of the topological pressure. We further show that the generalized pressure function is not computable for a large set of shift spaces and potentials . Along the way of developing these computability results, we derive several ergodic-theoretical properties of coded shifts which are of independent interest beyond the realm of computability. The topic of the talk is joint work with Michael Burr (Clemson U.), Shuddho Das (Texas Tech) and Yun Yang (Virginia Tech).

Next Week in Logic at CUNY:

- - - - Monday, May 6, 2024 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 6, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395

Lorenzo Rossi (Turin)
Title: Alethic pluralism and Kripkean truth

Abstract: According to alethic pluralism, there is more than one way of being true: truth is not unique, in that there is a plurality of truth properties each of which pertains to a specific domain of discourse. This paper shows how such a plurality can be represented in a coherent formal framework by means of a Kripke-style construction that yields intuitively correct extensions for distinct truth predicates. The theory of truth it develops can handle at least three crucial problems that have been raised in connection with alethic pluralism: mixed compounds, mixed inferences, and semantic paradoxes.

Note: This is joint work with Andrea Iacona (Turin) and Stefano Romeo (Turin).

- - - - Tuesday, May 7, 2024 - - - -

- - - - Wednesday, May 8, 2024 - - - -

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

Speaker: Juan Orendain, Case Western Univeristy.

Date and Time: Wednesday May 8, 2024, 7:00 - 8:30 PM. ZOOM TALK.

Title: Canonical squares in regularly framed bicategories.

- - - - Thursday, May 9, 2024 - - - -

- - - - Friday, May 10, 2024 - - - -

Logic Workshop
CUNY Graduate Center
Friday May 10, 2:00pm-3:30pm, Room 5417

Roman Kossak, CUNY
The lattice problem for models of arithmetic

The lattice problem for models of PA is to determine which lattices can be represented either as lattices of elementary substructures of a model of PA or, more generally, which can be represented as lattices of elementary substructures of a model N that contain a given elementary substructure M of N.

Since the 1970's, the problem generated much research with highly nontrivial results with proofs combining specific methods in the model theory of arithmetic with lattice theory and various combinatorial theorems. The problem has a definite answer in the case of distributive lattices, and, despite much effort, there are still many open questions in the nondistributive case. I will briefly survey some early results and present a few proofs that illustrate the difference between the distributive and nondistributive cases.

- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT

Northeast Model Theory Day

We are pleased to announce that Wesleyan University in Middletown, CT will be hosting a Northeast Model Theory Day on Saturday May 4, 2024. This one-day meeting is the first in what we hope will become an annual series, bringing together those interested in model theory from across the region.

Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)

All are welcome, but please register by Monday, April 22nd. Limited travel support is available. For more information and registration, please visit http://nemtd24.wescreates.wesleyan.edu/

NEMTD 2024 sponsored by the Mid-Atlantic Mathematical Logic Seminar (NSF grant #DMS-1834219) and the Wesleyan Department of Mathematics and Computer Science.
Organizers: Alex Kruckman, Rehana Patel, Alex Van Abel. Contact akruckman@wesleyan.edu with any questions.

- - - - Web Site - - - -

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

-------- ADMINISTRIVIA --------

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

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

Cross-Alps Logic Seminar (speaker: Spencer Unger)

Cross-Alps Logic Seminar

4/29/2024 6:58:52

On Friday 03.05.2024 at 16.00 CEST
Spencer Unger (University of Toronto)
will give a talk on
Iterated ultrapower methods

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

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

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

All the best,

Vincenzo

This Week in Logic at CUNY

4/28/2024 22:30:00

This Week in Logic at CUNY:

*** CUNY SPRING RECESS APRIL 22 - 30 ***

- - - - Monday, Apr 29, 2024 - - - -

Rutgers Logic Seminar
Monday Apr 29, 3:30pm Hill Center, Hill 705

Gabe Goldberg, Berkeley

Generalizations of the Ultrapower Axiom

Logic and Metaphysics Workshop
Date: Monday, April 29, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395

Anandi Hattiangadi (Stockholm).
Title: Physicalism, intentionality and normativity: The essential explanatory gap

Abstract: In this paper, I present an explanatory gap argument against the view that the semantic facts are fully grounded in the physical facts. Unlike traditional explanatory gap arguments, which stem from the failure of analytic reductive explanation, the explanatory gap I point to stems from the failure of metaphysical explanation. I argue for the following theses. (i) Physicalist grounding claims are metaphysically necessary, if true. (ii) To be explanatorily adequate, these grounding claims must be deducible from facts about essence. (iii) Semantico-physical grounding claims are possibly false, not (only) because they are conceivably false, but because they cannot be deduced from facts about essence. (iv) Semantic properties are essentially weakly normative: it lies in their natures to have correctness conditions and subjectively rationalize—rather than merely cause—behaviour. This gives rise to an explanatory gap that indicates that the semantic facts are not fully grounded in the physical facts.

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