KGRC Set Theory talk November 7
Cross-Alps Logic Seminar (speaker: Raphaël Carroy)
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
KGRC Set Theory Talk, November 14
This Week in Logic at CUNY
Monday November 11, 3:30pm, Rutgers University, Hill Center, Hill 705
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 - - - -
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 , , , and . 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 - - - -
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
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.
- - - - Thursday, Nov 14, 2024 - - - -
- - - - Friday, Nov 15, 2024 - - - -
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.
- - - - Monday, Nov 18, 2024 - - - -
Monday November 18, 3:30pm, Rutgers University, Hill Center, Hill 705
Two-cardinal derived topologies
Logic and Metaphysics Workshop
Date: Monday, November 18, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
- - - - 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 - - - -
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
- - - - 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
Logic Seminar 13.11.2024 at 17:00 hrs at NUS by Dilip Raghavan
Set theory and topology seminar 12.11.2024 Marcin Michalski
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)
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
This Week in Logic at CUNY
Monday November 18, 3:30pm, Rutgers University, Hill Center, Hill 705
Two-cardinal derived topologies
Logic and Metaphysics Workshop
Date: Monday, November 18, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
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 of compositional truth for arithmetical sentences can become non-conservative over 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 which is a propositional tautology, is true in the sense of the truth predicate. It is an open problem whether this axiom together with is conservative over .
In our talk, we will show that if is a model of satisfying the propositional soundness principle, then satisfies a certain amount of saturation: if is a sequence of sentences such that for any standard , is true in the sense of the truth predicate, then there is a nonstandard such that for each , 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 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 - - - -
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 - 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 ) which regards the mutual relationship between superstrong and tall cardinals. Time permitting we shall discuss the interplay between and - and propose a few open questions.
Logic Workshop
CUNY Graduate Center
Friday, November 22, 2:00pm-3:30pm, Room 4419
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 is an age, a -limit is a countable structure such that every finitely generated substructure of is in . A -limit is universal if every -limit embeds in . It is well-known that has the amalgamation property (AP) if and only if 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 , it is not equivalent to any finitary diagrammatic property like AP. More precisely, we show that for ages in a fixed sufficiently rich language , the property of admitting a universal limit is complete coanalytic. This is joint work with Aristotelis Panagiotopoulos.
- - - - Monday, Nov 25, 2024 - - - -
Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, November 25, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
- - - - 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 - - - -
- - - - 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
60th Nankai Logic Colloquium
KGRC Set Theory talks November 26--November 28
Set theory and topology seminar 26.11.2024 Łukasz Mazurkiewicz
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
Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, November 25, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
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 - - - -
- - - - Monday, Dec 2, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, December 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
- - - - 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
Logic Seminar 26/11/2024 14:00 hrs by Patrick Lutz at NUS - Note the time and place
Wednesday seminar
KGRC talks December 5
Set theory and topology seminar 3.02.2024 Aleksander Cieślak
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
Logic and Metaphysics Workshop
Date: Monday, December 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
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.
- - - - Monday, Dec 9, 2024 - - - -
Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, December 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
- - - - 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
UPDATE: This Week in Logic at CUNY
Logic and Metaphysics Workshop
Date: Monday, December 2, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
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.
- - - - Monday, Dec 9, 2024 - - - -
Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, December 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
- - - - 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)
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
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
Rutgers Logic Seminar
Monday November 25, 3:30pm, Rutgers University, Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, December 9, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
Leszek Kołodziejczyk, University of Warsaw
Models of fragments of PA with low Scott rank
The infinitary logic 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 sentence. This gives rise to a particular way of measuring the complexity of countable structures: there is a natural alternation hierarchy of formulas, and the Scott rank of a structure is the smallest ordinal such that can be described up to isomorphism by a 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 has Scott rank at least omega, that all other nonstandard models of must have rank at least , and that recursively saturated models of have rank exactly . This naturally leads one to ask about possible Scott ranks of models of subtheories of . In particular: what is the lowest possible Scott rank of a structure satisfying ? What about ?
We prove that every nonstandard model of must have Scott rank at least . Moreover, this lower bound is tight: it is realized both by the most familiar models of , namely pointwise -definable substructures of models of , and by the most familiar models of , namely initial segments generated by the -definables of models of . Time permitting, we also hope to mention a few other facts about Scott ranks of models of fragments of .
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 - - - -
- - - - 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
Wednesday seminar
Logic Seminar 18 Dec 2024 17:00 hrs at NUS by Manlio Valenti
Wednesday seminar
Set theory and topology seminar 17.12.2024 Serhii Bardyla
Schur ultrafilters and Bohr compactifications of topological groups.
will be presented by
Serhii Bardyla
Abstract: After a brief introduction to semigroups of ultrafilters, we shall discuss Schur ultrafilters on groups and with their help give a new description of Bohr compactifications of topological groups. Also, we show that Schur ultrafilters are crucial in distinguishing which chart group is a topological group. Namely, a chart group G is a (compact) topological group if and only if each Schur ultrafilter on G converges to the unit of G.
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
64th Nankai Logic Colloquium
65th Nankai Logic Colloquium
66th Nankai Logic Colloquium
Title: The 66th Nankai Logic Colloquium-- Kyle Gannon
Time: 16:00pm, Jan. 03, 2025(Beijing Time)
Zoom Number: 347 405 3484
Passcode: 477893
Wednesday seminar
KGRC talks January 9
This Week in Logic at CUNY - Special Announcement
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
Wednesday seminar
Cross-Alps Logic Seminar for World Logic Day (speaker: Jouko Väänänen)
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
KGRC talk January 23
This Week in Logic at CUNY
- - - - Monday, Jan 27, 2025 - - - -
Monday January 27, 3:30pm, Rutgers University, Hill Center, Hill 705
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
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 - - - -
Friday, February 7, 11:00am NY time, Room TBD
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
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.
CUNY Graduate Center
Friday, February 7, 12:30pm NY time, Room: 5417 (NOTE ROOM CHANGE!)
CUNY Graduate Center
Friday, February 7, 2:00pm-3:30pm, Room 5417 (NOTE ROOM CHANGE)
- - - - 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
This Week in Logic at CUNY
- - - - Monday, Feb 3, 2025 - - - -
Logic and Metaphysics Workshop
NOTE NEW TIME AND ROOM
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 - - - -
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 - - - -
Friday, February 7, 11:00am NY time, Room TBD
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
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.
CUNY Graduate Center
Friday, February 7, 12:30pm NY time, Room: 5417 (NOTE ROOM CHANGE!)
CUNY Graduate Center
Friday, February 7, 2:00pm-3:30pm, Room 5417 (NOTE ROOM CHANGE)
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 , for and . 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 to some other equivalence relation.
For 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 ; Larson and Zapletal characterized the analytic equivalence relations above 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 , when , based on Baire-category methods. As corollaries, we conclude that is 'regular' (answering a question of Clemens), and that is 'in the spectrum of the meager ideal' (extending a result of Kanovei, Sabok, and Zapletal for ).
- - - - Monday, Feb 10, 2025 - - - -
Monday February 10, 3:30pm, Rutgers University, Hill Center, Hill 705
Room: Graduate Center Room 7395
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 - - - -
Friday, February 14, 11:00am NY time, Room TBD
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
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.
- - - - 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 5 February 2025 17:00 hrs at NUS
Wednesday seminar
This Week in Logic at CUNY
Monday February 10, 3:30pm, Rutgers University, Hill Center, Hill 705
Room: Graduate Center Room 7395
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 - - - -
Friday, February 14, 11:00am NY time, Room TBD
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
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.
CUNY Graduate Center
Friday, February 14, 12:30pm NY time, Room: 5417
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'.
- - - - 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 - - - -
CUNY Graduate Center
Friday, February 21, 2:00pm-3:30pm, Room 5417
- - - - 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 by Tatsuta Makoto on 19 Feb 2025 at 17:00 hrs
This 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 - - - -
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.
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.
- - - - Monday, Feb 24, 2025 - - - -
Monday February 24, 3:30pm, Rutgers University, Hill Center, Hill 705
First-order sentences in random groups
Room: Graduate Center Room 7395
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 - - - -
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
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 - - - -
Friday, February 28, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
CUNY Graduate Center
Friday, February 28, 12:30pm NY time, Room: 5417
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'.
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'.
- - - - 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.
67th Nankai Logic Colloquium
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
Logic Seminar on 5 March 2025 17:00 hrs by Subin Pulari at NUS
Wednesday seminar
This Week in Logic at CUNY
Monday February 24, 3:30pm, Rutgers University, Hill Center, Hill 705
First-order sentences in random groups
Room: Graduate Center Room 7395
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 - - - -
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
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 - - - -
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.
CUNY Graduate Center
Friday, February 28, 12:30pm NY time, Room: 5417
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'.
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'.
- - - - Monday, Mar 3, 2025 - - - -
Room: Graduate Center Room 7395
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.
Monday March 3, 3:30pm, Rutgers University, Hill Center, Hill 705
- - - - Tuesday, Mar 4, 2025 - - - -
Athar Abdul-Quader Purchase College
- - - - Wednesday, Mar 5, 2025 - - - -
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
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 - - - -
Friday, March 7, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
Tom Benhamou Rutgers University
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.
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.
- - - - 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
Wednesday seminar
KGRC talks March 6
This Week in Logic at CUNY
Room: Graduate Center Room 7395
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.
Monday March 3, 3:30pm, Rutgers University, Hill Center, Hill 705
- - - - Tuesday, Mar 4, 2025 - - - -
Athar Abdul-Quader Purchase College
Spring 2025 (in-person + zoom)
Tuesday, March 4, Time 2:00 - 4:00 PM, Graduate Center, rm. 3308
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 - - - -
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
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 - - - -
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.
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.
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.
- - - - Monday, Mar 10, 2025 - - - -
Room: Graduate Center Room 7395
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.
Monday March 10, 3:30pm, Rutgers University, Hill Center, Hill 705
- - - - 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
[1] J. Funk, Toposes and C*-algebras, preprint, March 2024.
- - - - Thursday, Mar 13, 2025 - - - -
- - - - Friday, Mar 14, 2025 - - - -
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417
- - - - 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
Cross-Alps Logic Seminar (speaker: Sumun Iyer)
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
This Week in Logic at CUNY
Room: Graduate Center Room 7395
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.
Monday March 10, 3:30pm, Rutgers University, Hill Center, Hill 705
Galvin's Failure on Supercompactness Measures
- - - - Tuesday, Mar 11, 2025 - - - -
Athar Abdul-Quader Purchase College
Spring 2025 (in-person + zoom)
- - - - 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
[1] J. Funk, Toposes and C*-algebras, preprint, March 2024.
- - - - Thursday, Mar 13, 2025 - - - -
- - - - Friday, Mar 14, 2025 - - - -
Friday, March 14, 12:30pm NY time, Room: 5417
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.
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417
- - - - Monday, Mar 17, 2025 - - - -
Logic and Metaphysics Workshop
Date: Monday, March 3, 2-4pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
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
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 - - - -
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.
Friday, March 21, 12:30pm NY time, Room: 5417
Vince Guingona Towson University
Friday, March 21, 2:00pm-3:30pm, Room 5417
- - - - 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
70th Nankai Logic Colloquium
UPDATE - This Week in Logic at CUNY
Room: Graduate Center Room 7395
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.
Monday March 10, 3:30pm, Rutgers University, Hill Center, Hill 705
Galvin's Failure on Supercompactness Measures
- - - - Tuesday, Mar 11, 2025 - - - -
Athar Abdul-Quader Purchase College
Spring 2025 (in-person + zoom)
- - - - 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
[1] J. Funk, Toposes and C*-algebras, preprint, March 2024.
- - - - Thursday, Mar 13, 2025 - - - -
- - - - Friday, Mar 14, 2025 - - - -
Friday, March 14, 12:30pm NY time, Room: 5417
Alex Kruckman Wesleyan University
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417
- - - - Monday, Mar 17, 2025 - - - -
Logic and Metaphysics Workshop
Date: Monday, March 3, 2-4pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
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
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 - - - -
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.
Friday, March 21, 12:30pm NY time, Room: 5417
Vince Guingona Towson University
Friday, March 21, 2:00pm-3:30pm, Room 5417
- - - - 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
Room: Graduate Center Room 7395
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.
Monday March 10, 3:30pm, Rutgers University, Hill Center, Hill 705
Galvin's Failure on Supercompactness Measures
- - - - Tuesday, Mar 11, 2025 - - - -
Athar Abdul-Quader Purchase College
Spring 2025 (in-person + zoom)
- - - - 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
[1] J. Funk, Toposes and C*-algebras, preprint, March 2024.
- - - - Thursday, Mar 13, 2025 - - - -
- - - - Friday, Mar 14, 2025 - - - -
Friday, March 14, 12:30pm NY time, Room: 5417
Alex Kruckman Wesleyan University
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417
- - - - Monday, Mar 17, 2025 - - - -
Logic and Metaphysics Workshop
Date: Monday, March 3, 2-4pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
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
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 - - - -
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.
Friday, March 21, 12:30pm NY time, Room: 5417
Vince Guingona Towson University
Friday, March 21, 2:00pm-3:30pm, Room 5417
- - - - 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
- - - - Friday, Mar 14, 2025 - - - -
Friday, March 14, 12:30pm NY time, Room: 5417
Alex Kruckman Wesleyan University
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417
- - - - 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
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.
Date: Monday, March 17, 4-6pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
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
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 - - - -
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.
Friday, March 21, 12:30pm NY time, Room: 5417
Vince Guingona Towson University
Friday, March 21, 2:00pm-3:30pm, Room 5417
- - - - 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
- - - - Friday, Mar 14, 2025 - - - -
Friday, March 14, 12:30pm NY time, Room: 5417
Alex Kruckman Wesleyan University
CUNY Graduate Center
Friday, March 14, 2:00pm-3:30pm, Room 5417
- - - - 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
Title: Vagueness as dispersion
Date: Monday, March 17, 4-6pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
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
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 - - - -
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.
Friday, March 21, 12:30pm NY time, Room: 5417
Vince Guingona Towson University
Friday, March 21, 2:00pm-3:30pm, Room 5417
- - - - 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
This Week in Logic at CUNY
Logic and Metaphysics Workshop (NOTE BACK-TO-BACK TALKS TODAY)
Date: Monday, March 17, 2-4pm (NY time)
Room: Graduate Center Room 7395
Title: Vagueness as dispersion
Date: Monday, March 17, 4-6pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
Alf Dolich CUNY
Spring 2025 (in-person + zoom - for zoom link, please contact Sergei Artemov sartemov@gmail.com)
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
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 - - - -
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.
Friday, March 21, 12:30pm NY time, Room: 5417
Vince Guingona Towson University
Statistical Learning and Model Theory
Friday, March 21, 2:00pm-3:30pm, Room 5417
- - - - Monday, Mar 24, 2025 - - - -
Logic and Metaphysics Workshop
Date: Monday, March 24, 2-4pm (NY time)
Room: Graduate Center Room 7395
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.
Monday March 24, 3:30pm, Rutgers University, Hill Center, Hill 705
Gaps in Scott spectra of theories
- - - - Tuesday, Mar 25, 2025 - - - -
- - - - 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
- - - - Thursday, Mar 27, 2025 - - - -
- - - - Friday, Mar 28, 2025 - - - -
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.
Friday, March 28, 2:00pm-3:30pm, Room 5417
Aaron Anderson University of Pennsylvania
- - - - 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.
71st Nankai Logic Colloquium
Wednesday seminar
Logic Seminar 26 March 2025 17:00 hrs by Chong Chi Tat
Wednesday seminar
KGRC Set Theory talk March 27
This Week in Logic at CUNY
Logic and Metaphysics Workshop
Date: Monday, March 24, 2-4pm (NY time)
Room: Graduate Center Room 7395
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.
Monday March 24, 3:30pm, Rutgers University, Hill Center, Hill 705
Gaps in Scott spectra of theories
- - - - Tuesday, Mar 25, 2025 - - - -
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.
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
- - - - Thursday, Mar 27, 2025 - - - -
- - - - Friday, Mar 28, 2025 - - - -
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.
Friday, March 28, 2:00pm-3:30pm, Room 5417
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.
- - - - Monday, Mar 31, 2025 - - - -
Monday March 31, 3:30pm, Rutgers University, Hill Center, Hill 705
Examples of Distal Metric Structures
- - - - Tuesday, Apr 1, 2025 - - - -
- - - - Wednesday, Apr 2, 2025 - - - -
- - - - Thursday, Apr 3, 2025 - - - -
- - - - Friday, Apr 4, 2025 - - - -
CUNY Graduate Center
Friday, April 4, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
Friday, April 4, 2:00pm-3:30pm, Room 5417
There are a number of upcoming meetings of the Mid-Atlantic Mathematical Logic Seminar (MAMLS), listed below.
Place: University of Connecticut, Hartford
Saturday, April 5, 2025, 9am-6pm
Towson University, Towson, Maryland
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
KGRC Set Theory talks April 3
Wednesday seminar
This Week in Logic at CUNY
Monday March 31, 3:30pm, Rutgers University, Hill Center, Hill 705
Examples of Distal Metric Structures
- - - - Tuesday, Apr 1, 2025 - - - -
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 - - - -
CUNY Graduate Center
Friday, April 4, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
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.
- - - - Monday, Apr 7, 2025 - - - -
Monday April 7, 3:30pm, Rutgers University, Hill Center, Hill 705
Date: Monday, April 4/7, 2-4pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
Daniel Isaacson, Oxford University
Consideration of Dummett's claim that the meaning of 'natural number' is inherently vague
- - - - 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 - - - -
There are a number of upcoming meetings of the Mid-Atlantic Mathematical Logic Seminar (MAMLS), listed below.
Place: University of Connecticut, Hartford
Saturday, April 5, 2025, 9am-6pm
Towson University, Towson, Maryland
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
Monday March 31, 3:30pm, Rutgers University, Hill Center, Hill 705
Examples of Distal Metric Structures
- - - - Tuesday, Apr 1, 2025 - - - -
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.
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 - - - -
CUNY Graduate Center
Friday, April 4, 11:00am NY time, Room 6496
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
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.
- - - - Monday, Apr 7, 2025 - - - -
Monday April 7, 3:30pm, Rutgers University, Hill Center, Hill 705
Date: Monday, April 4/7, 2-4pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
Daniel Isaacson, Oxford University
Consideration of Dummett's claim that the meaning of 'natural number' is inherently vague
- - - - 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 - - - -
There are a number of upcoming meetings of the Mid-Atlantic Mathematical Logic Seminar (MAMLS), listed below.
Place: University of Connecticut, Hartford
Saturday, April 5, 2025, 9am-6pm
Towson University, Towson, Maryland
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.
Logic Seminar 2 April 2025 17:00 hrs at NUS by Jia Zekun
No Nankai Logic Colloquium this week
Wednesday seminar
KGRC Set Theory talk April 10
This Week in Logic at CUNY
Monday April 7, 3:30pm, Rutgers University, Hill Center, Hill 705
Date: Monday, April 4/7, 2-4pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
Daniel Isaacson, Oxford University
Consideration of Dummett's claim that the meaning of 'natural number' is inherently vague
- - - - 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 - - - -
- - - - Monday, Apr 14, 2025 - - - -
- - - - Tuesday, Apr 15, 2025 - - - -
- - - - Wednesday, Apr 16, 2025 - - - -
- - - - Thursday, Apr 17, 2025 - - - -
- - - - Friday, Apr 18, 2025 - - - -
Conference Announcement: Special Session to Honor Jim Schmerl on His 85th Birthday
VIrtual
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.
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.
Logic Seminar Wed 9 Apr 2025 17:00 hrs at NUS by Frank Stephan
73rd Nankai Logic Colloquium
Wednesday seminar
No Nankai Logic Colloquium this week
Logic Seminar 16 April 2025 17:00 hrs at NUS by Isabella Scott, Wellington
Wednesday seminar
This Week in Logic at CUNY
- - - - Monday, Apr 21, 2025 - - - -
Date: Monday, April 21, 2-4pm (NY time)
Room: Graduate Center Room 7395
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].
Monday April 21, 3:30pm, Rutgers University, Hill Center, Hill 705
Careful Iterations
- - - - Tuesday, Apr 22, 2025 - - - -
Virtual
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.
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 - - - -
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 .
Friday, April 25, 2:00pm-3:30pm, Room 5417
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
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.
Monday April 28, 3:30pm, Rutgers University, Hill Center, Hill 705
- - - - Tuesday, Apr 29, 2025 - - - -
- - - - Wednesday, Apr 30, 2025 - - - -
- - - - Thursday, May 1, 2025 - - - -
Model Theory Seminar
Friday, May 2, 12:30pm NY time, Room: 5417
Friday, May 2, 2:00pm-3:30pm, Room 5417
- - - - 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.
74th Nankai Logic Colloquium
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
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
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.
Monday April 28, 3:30pm, Rutgers University, Hill Center, Hill 705
- - - - 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 - - - -
Model Theory Seminar
Friday, May 2, 12:30pm NY time, Room: 5417
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.
Friday, May 2, 2:00pm-3:30pm, Room 5417
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.
- - - - Monday, May 5, 2025 - - - -
Rutgers Logic Seminar
Monday May 5, 3:30pm, Rutgers University, Hill Center, Hill 705
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 - - - -
Friday, May 9, 12:30pm NY time, Room: 5417
Friday, May 9, 2:00pm-3:30pm, Room 5417
- - - - 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
Wednesday seminar
This Week in Logic at CUNY
- - - - Monday, May 5, 2025 - - - -
Rutgers Logic Seminar
Monday May 5, 3:30pm, Rutgers University, Hill Center, Hill 705
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 - - - -
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.
Friday, May 9, 2:00pm-3:30pm, Room 5417
- - - - 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 - - - -
- - - - 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.
75th Nankai Logic Colloquium
Wednesday seminar
Wednesday seminar
KGRC Set Theory talk May 15
This Week in Logic at CUNY
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 - - - -
- - - - Monday, May 19, 2025 - - - -
- - - - Tuesday, May 20, 2025 - - - -
- - - - Wednesday, May 21, 2025 - - - -
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
Title: Gentle Introduction to Synthetic Differential Geometry --- Part two.
- - - - Thursday, May 22, 2025 - - - -
- - - - Friday, May 23, 2025 - - - -
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
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
KGRC Set Theory talk May 22
Wednesday seminar
This Week in Logic at CUNY
- - - - Tuesday, May 20, 2025 - - - -
- - - - Wednesday, May 21, 2025 - - - -
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
Title: Gentle Introduction to Synthetic Differential Geometry --- Part two.
- - - - Thursday, May 22, 2025 - - - -
- - - - Friday, May 23, 2025 - - - -
- - - - Monday, May 26, 2025 - - - -
- - - - Tuesday, May 27, 2025 - - - -
- - - - Wednesday, May 28, 2025 - - - -
- - - - Thursday, May 29, 2025 - - - -
- - - - Friday, May 30, 2025 - - - -
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
ESTS Colloquium today
Wednesday seminar
78th Nankai Logic Colloquium
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
UPDATE - This Week in Logic at CUNY
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
MLTCS colloquium and Wednesday seminar
KGRC Set Theory talk June 5
79th Nankai Logic Colloquium
MLTCS colloquium and Wednesday seminar
KGRC Set Theory talk June 12
Wednesday seminar
Wednesday seminar
KGRC Set Theory talks June 26
Wednesday seminar
Wednesday seminar
Wednesday seminar
Wednesday seminar
Wednesday seminar
Wednesday seminar
Wednesday seminar
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 - - - -
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
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.
Monday October 20, 3:30pm, Rutgers University, Hill 705
- - - - 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
- - - - Thursday, Oct 23, 2025 - - - -
- - - - Friday, Oct 24, 2025 - - - -
CUNY Graduate Center
Friday, October 24, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)
- - - - 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 on October 15, 16, and 17
Wednesday seminar (location change) and MLTCS Colloquium
This Week in Logic at CUNY
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 - - - -
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 basis theorem of and Vopěnka's theorem to conclude the following: If there is a proper class of Woodin cardinals, then every 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 - - - -
CUNY Graduate Center
Friday, October 17, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)
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
KGRC talks October 9
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
This Week in Logic at CUNY
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
Room: Graduate Center Room 8203
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)
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 - - - -
CUNY Graduate Center
Friday, October 10, 11:00am NY time
Virtual (email Victoria Gitman vgitman@gmail.com for meeting ID)
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 --------
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 talk September 30
81st Nankai Logic Colloquium
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.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
This Week in Logic at CUNY
Rutgers Logic Seminar
Measurable Brooks's Theorem for Directed Graphs
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.
- - - - Wednesday, Sep 24, 2025 - - - -
- - - - Thursday, Sep 25, 2025 - - - -
- - - - Friday, Sep 26, 2025 - - - -
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)
- - - - Monday, Sep 29, 2025 - - - -
Rutgers Logic Seminar
On the cofinality of ultrafilters
Date: Monday, September 29, 2-4pm (NY time)
Room: Graduate Center Room 8203
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 - - - -
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 --------
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Wednesday seminar
KGRC talk September 25
UPDATE - This Week in Logic at CUNY
- - - - Monday, Sep 15, 2025 - - - -
Rutgers Logic Seminar
On some PCF configurations
- - - - Tuesday, Sep 16, 2025 - - - -
- - - - Wednesday, Sep 17, 2025 - - - -
New York City Category Theory Seminar
Department of Mathematics
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 - - - -
CUNY Graduate Center
Friday, September 19, 2:00pm-3:30pm, Room 6417
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.
- - - - Monday, Sep 22, 2025 - - - -
Rutgers Logic Seminar
Measurable Brooks's Theorem for Directed Graphs
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.
- - - - Wednesday, Sep 24, 2025 - - - -
- - - - Thursday, Sep 25, 2025 - - - -
- - - - Friday, Sep 26, 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 --------
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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.
80th Nankai Logic Colloquium
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
This Week in Logic at CUNY
- - - - Monday, Sep 15, 2025 - - - -
Rutgers Logic Seminar
On some PCF configurations
- - - - Tuesday, Sep 16, 2025 - - - -
- - - - Wednesday, Sep 17, 2025 - - - -
New York City Category Theory Seminar
Department of Mathematics
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 - - - -
CUNY Graduate Center
Friday, September 19, 2:00pm-3:30pm, Room 6417
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.
- - - - Monday, Sep 22, 2025 - - - -
Rutgers Logic Seminar
Measurable Brooks's Theorem for Directed Graphs
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.
- - - - Wednesday, Sep 24, 2025 - - - -
- - - - Thursday, Sep 25, 2025 - - - -
- - - - Friday, Sep 26, 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 --------
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RIMS workshop on Set Theory 2025
Wednesday seminar
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
Cardinal Characteristics at Large Cardinals
- - - - Tuesday, Sep 9, 2025 - - - -
- - - - Wednesday, Sep 10, 2025 - - - -
- - - - Thursday, Sep 11, 2025 - - - -
- - - - Friday, Sep 12, 2025 - - - -
CUNY Graduate Center
Friday, September 12, 11:00am NY time
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.
- - - - 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
- - - - Monday, Sep 8, 2025 - - - -
Rutgers Logic Seminar
Cardinal Characteristics at Large Cardinals
- - - - Tuesday, Sep 9, 2025 - - - -
- - - - Wednesday, Sep 10, 2025 - - - -
- - - - Thursday, Sep 11, 2025 - - - -
- - - - Friday, Sep 12, 2025 - - - -
CUNY Graduate Center
Friday, September 12, 11:00am NY time
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.
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.
- - - - Monday, Sep 15, 2025 - - - -
Rutgers Logic Seminar
On some PCF configurations
- - - - Tuesday, Sep 16, 2025 - - - -
- - - - Wednesday, Sep 17, 2025 - - - -
New York City Category Theory Seminar
Department of Mathematics
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 - - - -
CUNY Graduate Center
Friday, September 19, 2:00pm-3:30pm, Room 6417
- - - - Other Logic News - - - -
CONFERENCE ANNOUNCEMENT:
Fall Fest 2025
September 26-28, New Brunswick
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)
-------- ADMINISTRIVIA --------
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Wednesday seminar
Set Theory and Topology Conference, Messina, Italy, September 3–6, 2025
Set Theory in the United Kingdom, Leeds, May 16, 2025
Conference on the occasion of Jörg Brendle's 60th birthday, Kobe, September 2-5
The Roaming Logic Conference, Warsaw, 9-11 May, 2025
Set Theory in the United Kingdom 15, London, February 20
Young Topology and Set Theory Meeting, Catania and Mexico City, January 29-30
Jörg Brendle's 60th birthday conference, Kobe, September 1-5, 2025
58th Nankai Logic Colloquium
Logic Seminar 6 Nov 2024 17:00 hrs by Michael Takaaki Leong at NUS
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
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 - - - -
- - - - Wednesday, Nov 6, 2024 - - - -
Philosophy Colloquium
Wednesday Nov 6, 4:15 P.M. to 6:15 P.M, CUNY Graduate Center Room 9206/9207
“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 - - - -
Thursday November 7, 2pm, Rutgers University, Hill Center, Hill 423
Generic dichotomies for Borel homomorphisms for the finite Friedman-Stanley jumps
- - - - Friday, Nov 8, 2024 - - - -
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
- - - - Monday, Nov 11, 2024 - - - -
Monday November 11, 3:30pm, Rutgers University, Hill Center, Hill 705
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 - - - -
- - - - Wednesday, Nov 13, 2024 - - - -
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
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.
- - - - Thursday, Nov 14, 2024 - - - -
- - - - Friday, Nov 15, 2024 - - - -
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.
- - - - 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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If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.
Set Theory in the United Kingdom, Cambridge, November 18, 2024
Summer School on Topology, dynamics, and logic in interaction, in Cetraro, Italy, September 1-5, 2025
Set theory and topology seminar 05.11.2024 Paweł Krupski
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
This Week in Logic at CUNY
MOPA (Models of Peano Arithmetic)
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.
Monday October 28, 3:30pm, Rutgers University, Hill Center, Hill 705
Date: Monday, October 28, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
- - - - 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
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 - - - -
- - - - Monday, Nov 4, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, November 4, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
- - - - 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 - - - -
Thursday November 7, 2pm, Rutgers University, Hill Center, Hill 423
Generic dichotomies for Borel homomorphisms for the finite Friedman-Stanley jumps
- - - - Friday, Nov 8, 2024 - - - -
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
- - - - 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 31.10.2024 Carlos López Callejas
High dimensional sequential compactness
will be presented by
Carlos López Callejas
Abstract: In this talk, we will explore a multidimensional version of sequential compactness introduced by Kubis and Szeptycki, known as n-sequential compactness (n-sc), where n is a natural number. They demonstrated that this property holds in compact metric spaces and showed that it induces a hierarchy of sequential compactness; that is, for any n, if a space X is (n+1)-sc, then it is also n-sc. The question they pose is whether this hierarchy is strict—specifically, whether for each n, it is possible to construct a space that is n-sc but not (n+1)-sc. In this presentation, we will discuss some recent progress on this question and mention further generalizations of sequential compactness to any countable ordinal.
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 29.10.2024 Francisco Santiago Nieto de la Rosa
A property of Laver forcing parameterized
will be presented by
Francisco Santiago Nieto de la Rosa
Abstract: Recently, Cieslak and Matinez-Celis have studied the Marczewski ideal associated with the Miller-Laver forcing \(m^0\) and \(l^0\). In particular, they considered parameterized versions of such forcings with ideals over omega (I) and considered the Marczewski ideal associated with these forcings \(m^0(I)\) and \(l^0(I)\). They are interested in studying the cofinality of such ideals. It is known that if the Laver forcing associated with I L(I) has the 1 to 1 or constant property, then \(l^0(I)\) has higher formality than the continuum. The mentioned mathematicians proved that for a certain class of ideals I, L(I) has the mentioned property, however they wonder what happens with ideals that do not belong to that class, specifically for Fin x Fin. In this talk we will give an affirmative answer to that question.
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 29.10.2024 Ángel Jareb Navarro Castillo
Determinacy of Filter Games from the Closed-Set Covering Property
will be presented by
Ángel Jareb Navarro Castillo
Abstract: In this talk, we will prove the determinacy of some filter games (for example, \(G(F, \omega, F^∗)\) and \(G(F, [\omega]^{<\omega}, F^+)\)), assuming that the dual ideal satisfies the Closed-Set Covering Property. As corollaries, we obtain that these games are determined for every analytic filter (by a theorem of Solecki) and for every set in the Solovay model (by a theorem of Di Prisco and Todorcevic).
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
KGRC Set Theory talks October 28--October 31
Wednesday seminar + colloquium of the MLTCS department
Logic Seminar at NUS Wed 30 Oct 2024 by Desmond Lau
KGRC Set Theory talk October 24
This Week in Logic at CUNY
Monday October 21, 3:30pm, Rutgers University, Hill Center, Hill 705
Elementarity of Subgroups and Complexity of Theories for Profinite Groups
Date: Monday, October 21, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
CUNY Graduate Center
Friday, October 25, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
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.
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.- - - - Monday, Oct 28, 2024 - - - -
MOPA (Models of Peano Arithmetic)
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.
Monday October 28, 3:30pm, Rutgers University, Hill Center, Hill 705
Date: Monday, October 28, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
- - - - 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 - - - -
- - - - 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
(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.
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
57th Nankai Logic Colloquium
This Week in Logic at CUNY
- - - - Monday, Oct 14, 2024 - - - -
Rutgers Logic Seminar
Monday October 13, 3:30pm, Rutgers University, Hill Center, Hill 705
From set theory to combinatorics of simplicial maps
- - - - Tuesday, Oct 15, 2024 - - - -
- - - - Wednesday, Oct 16, 2024 - - - -
- - - - Thursday, Oct 17, 2024 - - - -
- - - - Friday, Oct 18, 2024 - - - -
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 to 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 proves without Powerset is consistent with a Reinhardt embedding, but the embedding in the Matthews' model does not satisfy the cofinality (i.e., for every set there is such that ). In this talk, I will show from that without Powerset is consistent with a cofinal Reinhardt embedding.
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 , the set of continuous real-valued functions on a topological space with pointwise operations and order, the 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 - - - -
Monday October 21, 3:30pm, Rutgers University, Hill Center, Hill 705
Elementarity of Subgroups and Complexity of Theories for Profinite Groups
Date: Monday, October 21, 4.15-6.15pm (NY time)
Room: Graduate Center Room 4419
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 - - - -
CUNY Graduate Center
Friday, October 25, 11:00am NY time, Room 3207
Hybrid: Please email Victoria Gitman (vgitman@gmail.com) for zoom info.
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
KGRC Set Theory talk October 17
Set theory and topology seminar 15.10.2024 Piotr Borodulin-Nadzieja
Piotr Borodulin-Nadzieja
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
Logic Seminar Wed 9 Oct 2024 17:00 hrs at NUS
Wednesday seminar
This Week in Logic at CUNY (heads up, no email next week)
Rutgers Logic Seminar
Monday September 30, 3:30pm, Rutgers University, Hill Center, Hill 705
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 - - - -
- - - - Monday, Oct 7, 2024 - - - -
Monday October 7, 3:30pm, Rutgers University, Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, October 7, 4.15-6.15pm (NY time), GC 4419
- - - - 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)
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 - - - -
- - - - Other Logic News - - - -
- - - - Web Site - - - -
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
-------- ADMINISTRIVIA --------
To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.
If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.
KGRC Set Theory talks September 30 - October 4
Wednesday seminar
Wednesday seminar
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday September 23, 3:30pm, Rutgers University, Hill Center, Hill 705
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
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
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 - - - -
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 -ideal generated by closed null sets
Let denote the -ideal generated by closed null sets on . We show that the uniformity and the covering of can be added to Cichoń's maximum with distinct values, more specifically, it is consistent that holds.
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 from the universe of sets into a transitive submodel . The clear pattern the large cardinals in that region follow is that the closer the submodel is to 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 of (a fragment) of set theory (usually , the theory with powerset axiom removed). Elementary embeddings of are often by-definable with the existence of certain ultrafilters or systems of ultrafilters. The classical example is that is measurable if and only if there is a -complete ultrafilter on . The model is then the transitive collapse of the ultrapower of by . 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 follows the following template: for every , there is a (technical condition) model , with , for which there is an -ultrafilter on with (technical properties). A subset is an -ultrafilter if the structure , with a predicate for , satisfies that is a -complete ultrafilter on , meaning that measures all the sets in and its completeness applies to sequences that are elements of . The reason we need to add a predicate for is that in most interesting case, and in contrast to the situation with measurable cardinals, is not an element of (indeed in most cases, does not exist in ). While the structure usually satisfies some large fragment of , once, we add a predicate for the -ultrafilter , the structure can fail to satisfy even -separation. In this talk, I will discuss how smaller large cardinals follow the pattern that the more set theory the structure 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.
- - - - Monday, Sep 30, 2024 - - - -
Rutgers Logic Seminar
Monday September 30, 3:30pm, Rutgers University, Hill Center, Hill 705
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 - - - -
- - - - 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
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
- - - - Friday, Sep 20, 2024 - - - -
- - - - Monday, Sep 23, 2024 - - - -
Rutgers Logic Seminar
Monday September 9, 3:30pm, Rutgers University, Hill Center, Hill 705
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
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
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 - - - -
CUNY Graduate Center
Friday September 27, 2:00pm-3:30pm, Room 4419
- - - - 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 18 September 2024 16:45 hrs at NUS by Le Quy Thuong
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
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 - - - -
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.
- - - - 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)
- - - - 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
- - - - 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.
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
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 - - - -
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
Wednesday seminar
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.
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 -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
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 - - - -
CUNY Graduate Center
Friday September 13, 2:00pm-3:30pm, Room 6417 (NOTICE THE CHANGE! BACK TO OUR PRE-2023 ROOM)
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.
Location change -- Wednesday seminar -- Macpherson
Wednesday seminar -- Macpherson
Logic Seminar 28 August 2024 17:00 hrs by Linus Richter, NUS
Logic Seminar at NUS on 21 Aug 2024 17:00 hrs by Vo Ngoc Thieu
KGRC talk August 16
Logic Seminar 7 August 2024 17:00 hrs at NUS by Zhang Jing
Logic Seminar 31 July 2024 17:00 hrs at NUS by George Barmpalias, CAS
Kyoto University RIMS Set Theory Workshop, October 9-11, 2024
Wednesday seminar
Set theory and topology seminar 25.06.2024 everybody
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.
(on behalf of the organizers, i.e. Piotr Borodulin-Nadzieja, Paweł Krupski, Aleksandra Kwiatkowska, Grzegorz Plebanek, Robert Rałowski and myself)
Wednesday seminar
Set theory and topology seminar 18.06.2024 Aleksander Cieślak
Aleksander Cieślak
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
Wednesday seminar
KGRC talk June 20
56th Nankai Logic Colloquium
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).
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.
Best wishes,
Ming Xiao
Set theory and topology seminar 11.06.2024 Jadwiga Świerczyńska
Jadwiga Świerczyńska
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
KGRC talks June 11 -13
55th Nankai Logic Colloquium
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).
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.
Time :16:00pm, Jun. 7, 2024(Beijing Time)
Zoom Number : 436 658 8683
Passcode :477893
Best wishes,
Ming Xiao
Wednesday seminar
Cross-Alps Logic Seminar (speaker: Lorenz Halbeisen)
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
Set theory and topology seminar 4.06.2024 Andres Uribe-Zapata (TU Wien)
Andres Uribe-Zapata (TU Wien)
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.
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
KGRC Talk - June 6
54th Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the afternoon.
Our speaker this week will be 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).
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)
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
This Week in Logic at CUNY
- - - - 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.
- - - - Friday, May 24, 2024 - - - -
- - - - Monday, May 27, 2024 - - - -
- - - - Tuesday, May 28, 2024 - - - -
- - - - Wednesday, May 29, 2024 - - - -
- - - - Thursday, May 30, 2024 - - - -
- - - - Friday, May 31, 2024 - - - -
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 - May 24
Wednesday seminar
53rd Nankai Logic Colloquium
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.
_____________________________________________________________________
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
Hi everyone,
- - - - Tuesday, May 14, 2024 - - - -
Tuesday, May 14, Time 2:00 - 4:00 PM (EDT)
zoom link: ask Sergei Artemov sartemov@gmail.com
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 - - - -
- - - - 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.
- - - - Friday, May 24, 2024 - - - -
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
- - - - Tuesday, May 14, 2024 - - - -
Tuesday, May 14, Time 2:00 - 4:00 PM (EDT)
zoom link: ask Sergei Artemov sartemov@gmail.com
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 - - - -
- - - - Monday, May 20, 2024 - - - -
- - - - Tuesday, May 21, 2024 - - - -
- - - - Wednesday, May 22, 2024 - - - -
- - - - Thursday, May 23, 2024 - - - -
- - - - Friday, May 24, 2024 - - - -
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
Set Theory in the United Kingdom, Oxford, 16 May 2024
Wednesday seminar
KGRC Set Theory Talks - May 12-17
This Week in Logic at CUNY
Logic and Metaphysics Workshop
Date: Monday, May 6, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
CUNY Graduate Center
Virtual (email Victoria Gitman (vgitman@gmail.com) for meeting id)
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.
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 - - - -
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.
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.
- - - - 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 - - - -
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 8 May 2024 17:00 hrs at NUS
Fwd: 9 FMP: przestrzenie Banacha: geometria i operatory
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
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
UPDATE: This Week in Logic at CUNY
Rutgers Logic Seminar
Monday Apr 29, 3:30pm Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, April 29, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
CUNY Graduate Center
Friday May 3, 12:30pm NY time, Room: 6495
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.
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.
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).
- - - - Monday, May 6, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, May 6, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
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.
Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)
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.
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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Cross-Alps Logic Seminar (speaker: Spencer Unger)
Spencer Unger (University of Toronto)
will give a talk on
Iterated ultrapower methods
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday Apr 29, 3:30pm Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, April 29, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
- - - - Wednesday, May 1, 2024 - - - -
- - - - Thursday, May 2, 2024 - - - -
- - - - Friday, May 3, 2024 - - - -
CUNY Graduate Center
Friday May 3, 12:30pm NY time, Room: 6495
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.
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.
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).
- - - - Monday, May 6, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, May 6, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
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.
Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)
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.
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
-------- ADMINISTRIVIA --------
To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.
If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.
KGRC Set Theory Talk - May 2
Wednesday seminar
51st Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the afternoon.
Our speaker this week will be Jiachen Yuan from the University of Leeds. This talk is going to take place this Friday, Apr 26, from 4pm to 5pm(UTC+8, Beijing time).
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 51st Nankai Logic Colloquium -- Jiachen Yuan
Time :16:00pm, Apr. 26, 2024(Beijing Time)
Zoom Number : 734 242 5443
Passcode :477893
Link :https://zoom.us/j/7342425443?pwd=NnO2EFts9VOfCR9eDFUkoI3lNn2QTo.1&omn=84627872662
_____________________________________________________________________
Best wishes,
Ming Xiao
This Week in Logic at CUNY
*** CUNY SPRING RECESS APRIL 22 - 30 ***
Monday Apr 22, 3:30pm Hill Center, Hill 705
Dave Marker, University of Illinois at Chicago
Rigid real closed fields
- - - - Tuesday, Apr 23, 2024 - - - -
Computational Logic Seminar
Spring 2024 (online)
zoom link: ask Sergei Artemov (sartemov@gmail.com)
Speaker: Thomas Schlögl, Technische Universität Wien
Title: Epistemic Modeling of Truly Private Updates and a Glance at
a New Epistemic Model Checking and Visualization Tool
Abstract: Epistemic logic has been successfully applied to the modeling of epistemic and doxastic attitudes of agents in distributed systems. Dynamic Epistemic Logic (DEL) adds communication via model transforming updates. Since agents in distributed systems often exchange information without other agents knowing, however, the commonly known model updates in DEL are generally not adequate for describing fully private communication. In this talk, I will present a novel update mechanism for solving the fully private consistent update synthesis task: designing a model update that makes a given goal formula true while maintaining the consistency of the agents’ beliefs.
In addition, I will provide a first glimpse of the alpha version of a performant epistemic model checking and visualization tool I am currently working on. Model-checking allows us to verify whether a finite-state model (typically represented as a Kripke structure) satisfies a given specification. Many model-checking tools exist for a variety of logical languages, including epistemic logic. To effectively support foundational theoretical research like developing sound and efficient fully private model updates, however, a tool is needed that simultaneously provides:
.) a flexible and intuitive user interface,
.) powerful visualization capabilities for large models (>10,000 states),
.) a performant model-checking algorithm that also provides explanations/proofs/counter-examples
.) easy extendability w.r.t. logical language features and model generation/updates
- - - - Wednesday, Apr 24, 2024 - - - -
- - - - Thursday, Apr 25, 2024 - - - -
- - - - Friday, Apr 26, 2024 - - - -
*** CUNY SPRING RECESS APRIL 22 - 30 ***
Logic and Metaphysics Workshop
Date: Monday, April 29, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
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 - - - -
- - - - Wednesday, May 1, 2024 - - - -
- - - - Thursday, May 2, 2024 - - - -
- - - - Friday, May 3, 2024 - - - -
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.
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).
Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)
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.
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
Set theory and topology seminar 23.04.2024 Tomasz Żuchowski
Tomasz Żuchowski
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
KGRC Talks - April 25
50th Nankai Logic Colloquium
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.
Time(Stevo Todorcevic) :14:30pm, Apr. 19, 2024(Beijing Time)
Time(Dilip Raghavan) :16:00pm, Apr. 19, 2024(Beijing Time)
Zoom Number : 734 242 5443
Passcode :477893
Link :https://zoom.us/j/7342425443?pwd=NnO2EFts9VOfCR9eDFUkoI3lNn2QTo.1&omn=81450804954
_____________________________________________________________________
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best wishes,
Ming Xiao
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday Apr 15, 3:30pm Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, April 15, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Imaging is Alpha + Aizerman
Abstract: I give a non-probabilistic account of the imaging revision process. Most familiar in its various probabilistic forms, imaging was introduced by David Lewis (1976) as the form of belief revision appropriate for supposing subjunctively that a hypothesis be true. It has played a central role in the semantics of subjunctive conditionals, in causal decision theory, and, less well known to philosophers, in the computational theory of information retrieval. In the economics literature, non-probabilistic imaging functions have been called “pseudo-rationalizable choice functions”. I show that the imaging functions are precisely those which satisfy both Sen’s Alpha Principle (aka “Chernoff’s Axiom”) and the Aizerman Axiom. This result allows us to see very clearly the formal relationship between non-probabilistic imaging and AGM revision (which is Alpha + Beta).
- - - - Tuesday, Apr 16, 2024 - - - -
Computational Logic Seminar
Spring 2024 (online)
Tuesday, April 16, Time 2:00 - 4:00 PM
zoom link: contact Sergei Artemov (sartemov@gmail.com)
Speaker: Lukas Zenger, University of Bern
Title: Intuitionistic modal logic with the master modality
- - - - Wednesday, Apr 17, 2024 - - - -
- - - - Thursday, Apr 18, 2024 - - - -
- - - - Friday, Apr 19, 2024 - - - -
CUNY Graduate Center
Friday April 19, 2:00pm-3:30pm, Room 5417
Some applications of model theory to lattice-ordered groups
When does a hyperarchimedean lattice-ordered group embed into a hyperarchimedean lattice-ordered group with strong unit? After explaining the meaning of this question, I will describe some partial answers obtained via model theory.
- - - - Monday, Apr 22, 2024 - - - -
*** CUNY SPRING RECESS APRIL 22 - 30 ***
- - - - Tuesday, Apr 23, 2024 - - - -
*** CUNY SPRING RECESS APRIL 22 - 30 ***
- - - - Wednesday, Apr 24, 2024 - - - -
*** CUNY SPRING RECESS APRIL 22 - 30 ***
- - - - Thursday, Apr 25, 2024 - - - -
*** CUNY SPRING RECESS APRIL 22 - 30 ***
- - - - Friday, Apr 26, 2024 - - - -
Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)
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.
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 - April 18
Set theory and toplogy seminar 16.04.2024 Krzysztof Zakrzewski (UW)
Krzysztof Zakrzewski (MIM UW)
Wednesday seminar
Two Related Seminars in Geometry and Topology by Shlpak Banerjee and in Logic by Philipp Kunde on Wednesday 17 April 2024
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday Apr 8, Hill Center, Hill 705, SPECIAL TIME: 4:00pm
Jing Zhang, Toronto
Squares, ultrafilters and forcing axioms
Logic and Metaphysics Workshop
Date: Monday, April 8, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Social construction and meta-ground
Abstract: The notion of social construction plays an important role in many areas of social philosophy, including the philosophy of gender, the philosophy of race, and social ontology. But it is far from clear how this notion (or cluster of notions) is to be understood. One promising proposal, which has been championed in recent years by Aaron Griffith (2017, 2018) and Jonathan Schaffer (2017), is that the notion of constitutive social construction may be analyzed in terms of the notion of metaphysical grounding. In this paper, I argue that a simple ground-theoretic analysis of social construction is subject to two sorts of problem cases and that existing ground-theoretic accounts do not avoid these problems. I then develop a novel ground-theoretic account of social construction in terms of meta-ground, and I argue that it avoids the problems. The core idea of the account is that in cases of social construction, the meta-ground of the relevant grounding fact includes a suitable connective social fact.
- - - - Tuesday, Apr 9, 2024 - - - -
MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Virtual (email Victoria Gitman for meeting id)
Tuesday, April 9, 1pm
Athar Abdul-Quader, Purchase College
Representations of lattices
- - - - Wednesday, Apr 10, 2024 - - - -
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
Date and Time: Wednesday April 10, 2024, 7:00 - 8:30 PM. IN-PERSON
Title: Pulse Diagrams and Category Theory.
Abstract: ``Pulse diagrams'' are motivated by the ubiquity of pulsation in biology, from action potentials, to heartbeat, to respiration, and at longer time-scales to circadian rhythms and even to human behavior. The syntax of the diagrams is simple, and the semantics are easy to define and simulate with Python code. They express behaviors of parts and wholes as in categorical mereology, but are missing a compositional framework, like string diagrams. Examples to discuss include cellular automata, leaky-integrate-and-fire neurons, harmonic frequency generation, Gillespie algorithm for the chemical master equation, piecewise-linear genetic regulatory networks, Lotka-Volterra systems, and if time permits, aspects of the adaptive immune system. The talk is more about questions than about answers.
- - - - Thursday, Apr 11, 2024 - - - -
- - - - Friday, Apr 12, 2024 - - - -
CUNY Graduate Center
Friday, April 12, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Boban Velickovic University of Paris
Logic Workshop
CUNY Graduate Center
Friday April 12, 2:00pm-3:30pm, Room 5417
Hans Schoutens, CUNY
Geometric tools for the decidability of the existential theory of
I will give a brief survey how tools from algebraic geometry can be used in finding solutions to Diophantine equations over and similar rings. These tools include Artin approximation, arc spaces, motives and resolution of singularities. This approach yields the definability of the existential theory of (in the ring language with a constant for ) contingent upon the validity of resolution of singularities (Denef-Schoutens). Anscombe-Fehm proved a weaker result using model-theoretic tools and together with Dittmann, they gave a proof assuming only the weaker 'local uniformization conjecture.'
- - - - Monday, Apr 15, 2024 - - - -
Rutgers Logic Seminar
Monday Apr 15, 3:30pm Hill Center, Hill 705
Logic and Metaphysics Workshop
Date: Monday, April 15, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Imaging is Alpha + Aizerman
Abstract: I give a non-probabilistic account of the imaging revision process. Most familiar in its various probabilistic forms, imaging was introduced by David Lewis (1976) as the form of belief revision appropriate for supposing subjunctively that a hypothesis be true. It has played a central role in the semantics of subjunctive conditionals, in causal decision theory, and, less well known to philosophers, in the computational theory of information retrieval. In the economics literature, non-probabilistic imaging functions have been called “pseudo-rationalizable choice functions”. I show that the imaging functions are precisely those which satisfy both Sen’s Alpha Principle (aka “Chernoff’s Axiom”) and the Aizerman Axiom. This result allows us to see very clearly the formal relationship between non-probabilistic imaging and AGM revision (which is Alpha + Beta).
- - - - Tuesday, Apr 16, 2024 - - - -
- - - - Wednesday, Apr 17, 2024 - - - -
- - - - Thursday, Apr 18, 2024 - - - -
- - - - Friday, Apr 19, 2024 - - - -
CUNY Graduate Center
Friday April 19, 2:00pm-3:30pm, Room 5417
Some applications of model theory to lattice-ordered groups
When does a hyperarchimedean lattice-ordered group embed into a hyperarchimedean lattice-ordered group with strong unit? After explaining the meaning of this question, I will describe some partial answers obtained via model theory.
Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)
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.
Logic Seminar Tuesday 9 April 2023 by Piotr Kowalski
KGRC Talk - April 11
Nankai Logic Colloquium paused for two weeks
Set theory and topology seminar 9.04.2024 Jakub Rondos
Jakub Rondos (University of Vienna)
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
Cross-Alps Logic Seminar (speaker: Luca Motto Ros)
This Week in Logic at CUNY
Logic and Metaphysics Workshop
Date: Monday, April 1, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Andrew Tedder (Vienna).
Title: Relevant logics as topical logics
Abstract: There is a simple way of reading a structure of topics into the matrix models of a given logic, namely by taking the topics of a given matrix model to be represented by subalgebras of the algebra reduct of the matrix, and then considering assignments of subalgebras to formulas. The resulting topic-enriched matrix models bear suggestive similarities to the two-component frame models developed by Berto et. al. in Topics of Thought. In this talk I’ll show how this reading of topics can be applied to the relevant logic R, and its algebraic characterisation in terms of De Morgan monoids, and indicate how we can, using this machinery and the fact that R satisfies the variable sharing property, read R as a topic-sensitive logic. I’ll then suggest how this approach to modeling topics can be applied to a broader range of logics/classes of matrices, and gesture at some avenues of research.
- - - - Tuesday, Apr 2, 2024 - - - -
MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Virtual (email Victoria Gitman for meeting id)
Tuesday, April 2, 1pm
Athar Abdul-Quader, Purchase College
Representations of lattices
Following up on the series of talks on the history of the problem, in this talk we will discuss the main technique for realizing finite lattices as interstructure lattices, due to Schmerl in 1986. We will motivate this technique by studying an example: the Boolean algebra . We will see how we can modify the technique to produce elementary extensions realizing specific ranked lattices to ensure that such extensions are end, cofinal, or mixed extensions.
Spring 2024 (online)
Abstract: In this presentation I focus on a framework that generalizes dynamic epistemic logic in order to model a wider range of scenarios including those in which agents read or communicate (or somehow gain access to) all the information stored at specific sources, or possessed by some other agents (including information of a non-propositional nature, such as data, passwords, secrets etc). The resulting framework allows one to reason about the state of affairs in which one agent (or group of agents) has ‘epistemic superiority’ over another agent (or group). I will present different examples of epistemic superiority and I will draw a connection to the logic of functional dependence by A. Baltag and J. van Benthem. At the level of group attitudes, I will further introduce the new concept of 'common distributed knowledge', which combines features of both common knowledge and distributed knowledge. This presentation is based on joint work with A. Baltag in [1].
[1] A. Baltag and S. Smets, Learning what others know, in L. Kovacs and E. Albert (eds.), LPAR23 proceedings of the International Conference on Logic for Programming, AI and Reasoning, EPiC Series in Computing, 73:90-110, 2020. https://doi.org/10.29007/plm4
- - - - Wednesday, Apr 3, 2024 - - - -
- - - - Thursday, Apr 4, 2024 - - - -
- - - - Friday, Apr 5, 2024 - - - -
April 5, Friday, 10 AM
Zoom meeting, please contact Rohit Parikh for zoom link
CUNY Graduate Center
Friday, April 5, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Kameryn Williams Bard College at Simon's Rock
Logic Workshop
CUNY Graduate Center
Friday April 5, 2:00pm-3:30pm, Room 5417
Decision problem for groups as equivalence relations
In 1911, Dehn proposed three decision problems for finitely presented groups: the word problem, the conjugacy problem, and the isomorphism problem. These problems have been central to both group theory and logic, and were each proven to be undecidable in the 50's. There is much current research studying the decidability of these problems in certain classes of groups.
Classically, when a decision problem is undecidable, its complexity is measured using Turing reducibility. However, Dehn's problems can also be naturally thought of as computably enumerable equivalence relations (ceers). We take this point of view and measure their complexity using computable reductions. This yields behaviors different from the classical context: for instance, every Turing degree contains a word problem, but not every ceer degree does. This leads us to study the structure of ceer degrees containing a word problem and other related questions.
- - - - Monday, Apr 8, 2024 - - - -
Rutgers Logic Seminar
Monday Apr 8, 3:30pm, Hill Center, Hill 705
Jing Zhang
Logic and Metaphysics Workshop
Date: Monday, April 8, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Social construction and meta-ground
Abstract: The notion of social construction plays an important role in many areas of social philosophy, including the philosophy of gender, the philosophy of race, and social ontology. But it is far from clear how this notion (or cluster of notions) is to be understood. One promising proposal, which has been championed in recent years by Aaron Griffith (2017, 2018) and Jonathan Schaffer (2017), is that the notion of constitutive social construction may be analyzed in terms of the notion of metaphysical grounding. In this paper, I argue that a simple ground-theoretic analysis of social construction is subject to two sorts of problem cases and that existing ground-theoretic accounts do not avoid these problems. I then develop a novel ground-theoretic account of social construction in terms of meta-ground, and I argue that it avoids the problems. The core idea of the account is that in cases of social construction, the meta-ground of the relevant grounding fact includes a suitable connective social fact.
- - - - Tuesday, Apr 9, 2024 - - - -
- - - - Wednesday, Apr 10, 2024 - - - -
- - - - Thursday, Apr 11, 2024 - - - -
- - - - Friday, Apr 12, 2024 - - - -
CUNY Graduate Center
Friday, April 12, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Boban Velickovic University of Paris
Logic Workshop
CUNY Graduate Center
Friday April 12, 2:00pm-3:30pm, Room 5417
Hans Schoutens, CUNY
Geometric tools for the decidability of the existential theory of
I will give a brief survey how tools from algebraic geometry can be used in finding solutions to Diophantine equations over and similar rings. These tools include Artin approximation, arc spaces, motives and resolution of singularities. This approach yields the definability of the existential theory of (in the ring language with a constant for ) contingent upon the validity of resolution of singularities (Denef-Schoutens). Anscombe-Fehm proved a weaker result using model-theoretic tools and together with Dittmann, they gave a proof assuming only the weaker 'local uniformization conjecture.'
Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)
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.
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
Wednesday seminar
49th Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the afternoon.
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 49th Nankai Logic Colloquium -- Aristotelis Panagiotopoulos
Time :16:00pm, Mar. 29, 2024(Beijing Time)
Zoom Number : 734 242 5443
Passcode :477893
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best wishes,
Ming Xiao
Logic Seminar Talks 27 March 2024 and 3 April 2024 at NUS
UPDATE: This Week in Logic at CUNY
Rutgers Logic Seminar
Monday Mar 25, 3:30pm, Hill Center, Hill 705
Date: Monday, March 25, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: A moderate theory of overall resemblance
Abstract: This paper defends the moderate theory of overall resemblance stated by: A) y is at least as similar to x as z is iff: i) every resemblance property shared by x and z is also shared by x and y, and ii) for any resemblance family of properties F, y is at least as similar to x as z is with respect to F. In this account, a resemblance property is a property that corresponds to a genuine respect in which two things can resemble each other, whereas a resemblance family is a set of properties with respect to which things can be more or less similar to each other. An example of a resemblance property is being cubical, an example of a non-resemblance property is being either a gold cube or a silver sphere, and an example of a resemblance family is the set of specific mass properties.
- - - - Tuesday, Mar 26, 2024 - - - -
MOPA (Models of Peano Arithmetic)
CUNY Graduate Center
Virtual (email Victoria Gitman for meeting id)
Tuesday, March 26, 1pm
Roman Kossak, CUNY
The lattice problem for models of PA: Part ii
The lattice problem for models of PA is to determine which lattices can be represented either as lattices of elementary substructures of a model of PA or, more generally, which can be represented as lattices of elementary substructures of a model N that contain a given elementary substructure M of N. I will talk about the history of the problem, from the seminal paper of Haim Gaifman from 1976 and other early results to some recent work of Jim Schmerl. There is much to talk about.
Computational Logic Seminar
Spring 2024 (online)
Tuesday, March 26 Time 2:00 - 4:00 PM
zoom link: contact Sergei Artemov (sartemov@gmail.com)
Speaker: Thomas Studer, University of Bern
Title: Simplicial Complexes for Epistemic Logic
- - - - Wednesday, Mar 27, 2024 - - - -
- - - - Thursday, Mar 28, 2024 - - - -
- - - - Friday, Mar 29, 2024 - - - -
- - - - Monday, Apr 1, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, April 1, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Andrew Tedder (Vienna).
Title: Relevant logics as topical logics
Abstract: There is a simple way of reading a structure of topics into the matrix models of a given logic, namely by taking the topics of a given matrix model to be represented by subalgebras of the algebra reduct of the matrix, and then considering assignments of subalgebras to formulas. The resulting topic-enriched matrix models bear suggestive similarities to the two-component frame models developed by Berto et. al. in Topics of Thought. In this talk I’ll show how this reading of topics can be applied to the relevant logic R, and its algebraic characterisation in terms of De Morgan monoids, and indicate how we can, using this machinery and the fact that R satisfies the variable sharing property, read R as a topic-sensitive logic. I’ll then suggest how this approach to modeling topics can be applied to a broader range of logics/classes of matrices, and gesture at some avenues of research.
- - - - Tuesday, Apr 2, 2024 - - - -
- - - - Wednesday, Apr 3, 2024 - - - -
- - - - Thursday, Apr 4, 2024 - - - -
- - - - Friday, Apr 5, 2024 - - - -
CUNY Graduate Center
Friday, April 5, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Kameryn Williams Bard College at Simon's Rock
Logic Workshop
CUNY Graduate Center
Friday April 5, 2:00pm-3:30pm, Room 5417
Decision problem for groups as equivalence relations
In 1911, Dehn proposed three decision problems for finitely presented groups: the word problem, the conjugacy problem, and the isomorphism problem. These problems have been central to both group theory and logic, and were each proven to be undecidable in the 50's. There is much current research studying the decidability of these problems in certain classes of groups.
Classically, when a decision problem is undecidable, its complexity is measured using Turing reducibility. However, Dehn's problems can also be naturally thought of as computably enumerable equivalence relations (ceers). We take this point of view and measure their complexity using computable reductions. This yields behaviors different from the classical context: for instance, every Turing degree contains a word problem, but not every ceer degree does. This leads us to study the structure of ceer degrees containing a word problem and other related questions.
Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)
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.
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
Set theory and topology seminar 26.03.2024 Tomasz Żuchowski
Tomasz Żuchowski
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday Mar 25, 3:30pm, Hill Center, Hill 705
Date: Monday, March 25, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: A moderate theory of overall resemblance
Abstract: This paper defends the moderate theory of overall resemblance stated by: A) y is at least as similar to x as z is iff: i) every resemblance property shared by x and z is also shared by x and y, and ii) for any resemblance family of properties F, y is at least as similar to x as z is with respect to F. In this account, a resemblance property is a property that corresponds to a genuine respect in which two things can resemble each other, whereas a resemblance family is a set of properties with respect to which things can be more or less similar to each other. An example of a resemblance property is being cubical, an example of a non-resemblance property is being either a gold cube or a silver sphere, and an example of a resemblance family is the set of specific mass properties.
- - - - Tuesday, Mar 26, 2024 - - - -
Computational Logic Seminar
Spring 2024 (online)
Tuesday, March 26 Time 2:00 - 4:00 PM
zoom link: contact Sergei Artemov (sartemov@gmail.com)
Speaker: Thomas Studer, University of Bern
Title: Simplicial Complexes for Epistemic Logic
- - - - Wednesday, Mar 27, 2024 - - - -
- - - - Thursday, Mar 28, 2024 - - - -
- - - - Friday, Mar 29, 2024 - - - -
- - - - Monday, Apr 1, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, April 1, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Andrew Tedder (Vienna).
Title: Relevant logics as topical logics
Abstract: There is a simple way of reading a structure of topics into the matrix models of a given logic, namely by taking the topics of a given matrix model to be represented by subalgebras of the algebra reduct of the matrix, and then considering assignments of subalgebras to formulas. The resulting topic-enriched matrix models bear suggestive similarities to the two-component frame models developed by Berto et. al. in Topics of Thought. In this talk I’ll show how this reading of topics can be applied to the relevant logic R, and its algebraic characterisation in terms of De Morgan monoids, and indicate how we can, using this machinery and the fact that R satisfies the variable sharing property, read R as a topic-sensitive logic. I’ll then suggest how this approach to modeling topics can be applied to a broader range of logics/classes of matrices, and gesture at some avenues of research.
- - - - Tuesday, Apr 2, 2024 - - - -
- - - - Wednesday, Apr 3, 2024 - - - -
- - - - Thursday, Apr 4, 2024 - - - -
- - - - Friday, Apr 5, 2024 - - - -
CUNY Graduate Center
Friday, April 5, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Kameryn Williams Bard College at Simon's Rock
Logic Workshop
CUNY Graduate Center
Friday April 5, 2:00pm-3:30pm, Room 5417
Decision problem for groups as equivalence relations
In 1911, Dehn proposed three decision problems for finitely presented groups: the word problem, the conjugacy problem, and the isomorphism problem. These problems have been central to both group theory and logic, and were each proven to be undecidable in the 50's. There is much current research studying the decidability of these problems in certain classes of groups.
Classically, when a decision problem is undecidable, its complexity is measured using Turing reducibility. However, Dehn's problems can also be naturally thought of as computably enumerable equivalence relations (ceers). We take this point of view and measure their complexity using computable reductions. This yields behaviors different from the classical context: for instance, every Turing degree contains a word problem, but not every ceer degree does. This leads us to study the structure of ceer degrees containing a word problem and other related questions.
Speakers:
Paul Baginski (Fairfield)
Artem Chernikov (Maryland)
Alf Dolich (CUNY)
Alexei Kolesnikov (Towson)
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.
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
Wednesday seminar
48th Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the afternoon.
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 48th Nankai Logic Colloquium -- Dominique LecomteTime :16:00pm, Mar. 22, 2024(Beijing Time)
Zoom Number : 734 242 5443
Passcode :477893
Link :https://zoom.us/j/7342425443?pwd=NnO2EFts9VOfCR9eDFUkoI3lNn2QTo.1&omn=87996387829
_____________________________________________________________________
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best wishes,
Ming Xiao
Logic Seminar 20 March 2024 17:00 hrs by Sun Mengzhou
This Week in Logic at CUNY
Logic and Metaphysics Workshop
Date: Monday, March 18, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Modal quantifiers, potential infinity, and Yablo sequences
Abstract: When properly arithmetized, Yablo’s paradox results in a set of formulas which (with local disquotation in the background) turns out to be consistent, but omega-inconsistent. Adding either uniform disquotation or the omega-rule results in inconsistency. Since the paradox involves an infinite sequence of sentences, one might think that it doesn’t arise in finitary contexts. We study whether it does. It turns out that the issue depends on how the finitistic approach is formalized. On one of them, proposed by Marcin Mostowski, all the paradoxical sentences simply fail to hold. This happens at a price: the underlying finitistic arithmetic itself is omega-inconsistent. Finally, when studied in the context of a finitistic approach which preserves the truth of standard arithmetic, the paradox strikes back — it does so with double force, for now the inconsistency can be obtained without the use of uniform disquotation or the omega-rule.
Note: This is joint work with Rafał Urbaniak (Gdańsk).
- - - - Tuesday, Mar 19, 2024 - - - -
Roman Kossak, CUNY
The lattice problem for models of PA
The lattice problem for models of PA is to determine which lattices can be represented either as lattices of elementary substructures of a model of PA or, more generally, which can be represented as lattices of elementary substructures of a model N that contain a given elementary substructure M of N. I will talk about the history of the problem, from the seminal paper of Haim Gaifman from 1976 and other early results to some recent work of Jim Schmerl. There is much to talk about.
Spring 2024 (online)
Title: Logics of Intuitionistic Knowledge and Verification
The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL: http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker: Sina Hazratpour, Johns Hopkins University.
Date and Time: Wednesday March 20, 2024, 7:00 - 8:30 PM.
Title: Fibred Categories in Lean.
Abstract: Fibred categories are one of the most important and useful concepts in category theory and its application in categorical logic. In this talk I present my recent formalization of fibred categories in the interactive theorem prover Lean 4. I begin by highlighting certain technical challenges associated with handling the equality of objects and functors within the extensional dependent type system of Lean, and how they can be overcome. In this direction, I will demonstrate how we can take advantage of dependent coercion, instance synthesis, and automation tactics from the Lean toolbox. Finally I will discuss a formalization of Homotopy Type Theory in Lean 4 using a fired categorical framework.
- - - - Thursday, Mar 21, 2024 - - - -
- - - - Friday, Mar 22, 2024 - - - -
CUNY Graduate Center
Friday, March 22, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Arthur Apter, CUNY
A choiceless answer to a question of Woodin
In a lecture presented in July 2023, Moti Gitik discussed the following question from the 1980s due to Woodin, as well as approaches to its solution and why it is so difficult to solve:
Question: Assuming there is no inner model of ZFC with a strong cardinal, is it possible to have a model of ZFC such that ' and for every ', together with the existence of an inner model of ZFC such that for the so that and ' is measurable and '?I will discuss how to find answers to this question, if we drop the requirement that satisfies the Axiom of Choice. I will also briefly discuss the phenomenon that on occasion, when the Axiom of Choice is removed from consideration, a technically challenging question or problem becomes more tractable. One may, however, end up with models satisfying conclusions that are impossible in ZFC.
Reference: A. Apter, 'A Note on a Question of Woodin', Bulletin of the Polish Academy of Sciences (Mathematics), volume 71(2), 2023, 115--121.
CUNY Graduate Center
Mediate cardinals
In the late 1910s Bertrand Russell was occupied with two things: getting into political trouble for his pacifism and trying to understand the foundations of mathematics. His students were hard at work with him on this second occupation. One of those students was Dorothy Wrinch. In 1923 she gave a characterization of the axiom of choice in terms of a generalization of the notion of a Dedekind-finite infinite set. Unfortunately, her career turned toward mathematical biology and her logical work was forgotten by history.
This talk is part of a project of revisiting Wrinch's work from a modern perspective. I will present the main result of her 1923 paper, that AC is equivalent to the non-existence of what she termed mediate cardinals. I will also talk about some new independence results. The two main results are: (1) the smallest for which a -mediate cardinal exists can consistently be any regular and (2) the collection of regular for which exact -mediate cardinals exist can consistently be any class.
- - - - Monday, Mar 25, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, March 25, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: A moderate theory of overall resemblance
Abstract: This paper defends the moderate theory of overall resemblance stated by: A) y is at least as similar to x as z is iff: i) every resemblance property shared by x and z is also shared by x and y, and ii) for any resemblance family of properties F, y is at least as similar to x as z is with respect to F. In this account, a resemblance property is a property that corresponds to a genuine respect in which two things can resemble each other, whereas a resemblance family is a set of properties with respect to which things can be more or less similar to each other. An example of a resemblance property is being cubical, an example of a non-resemblance property is being either a gold cube or a silver sphere, and an example of a resemblance family is the set of specific mass properties.
- - - - Tuesday, Mar 26, 2024 - - - -
- - - - Wednesday, Mar 27, 2024 - - - -
- - - - Thursday, Mar 28, 2024 - - - -
- - - - Friday, Mar 29, 2024 - - - -
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
KGRC Talk - March 21
Set theory and topology seminar 19.03.2024 Piotr Szewczak
Piotr Szewczak (UKSW)
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
Wednesday seminar
47th Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the morning.
Our speaker this week will be Sumun Iyer from Cornell University. This talk is going to take place this Friday, Mar 15, from 9am to 10am(UTC+8, Beijing time).
This is going to be an online event. Follow the link below to join the Zoom meeting. Please use your real name to join the meeting.
Title :The 47th Nankai Logic Colloquium -- Sumun Iyer
Time :9:00am, Mar. 15, 2024(Beijing Time)
Zoom Number : 734 242 5443
Passcode :477893
Link :https://zoom.us/j/7342425443?pwd=EG6I3uatr8anqkk6HM5wZ9FKjhkjbC.1&omn=87197636384
_____________________________________________________________________
Best wishes,
Ming Xiao
This Week in Logic at CUNY
Logic and Metaphysics Workshop
Date: Monday, March 11, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Dispensing with the grounds of logical necessity
Abstract: Logical laws are typically conceived as being necessary. But in virtue of what is this the case? That is, what are the grounds of logical necessity? In this paper, I examine four different answers to this question in terms of: truth-conditions, invariance of truth-values under different interpretations, possible worlds, and brute facts. I ultimately find all of them wanting. I conclude that an alternative conception of logic that dispenses altogether with grounds of logical necessity provides a less troublesome alternative. I then indicate some of the central features of this conception.
- - - - Tuesday, Mar 12, 2024 - - - -
Albert Visser, Utrecht University
Restricted completions
This talk reports on research in collaboration with Ali Enayat and Mateusz Łełyk.
Steffen Lempp and Dino Rossegger asked: is there a consistent completion of that is axiomatised by sentences of bounded quantifier-alternation complexity? We show that there is no such restricted completion. We also show that, if one changes the measure of complexity to being , there is a restricted completion. Specifically, we show that the true theory of the non-negative part of can be axiomatised by a single sentence plus a set of -sentences.In our talk we will sketch these two answers. One of our aims is to make clear is that the negative answer for the case of quantifier-alternation complexity simply follows from Rosser's Theorem viewed from a sufficiently abstract standpoint.
- - - - Wednesday, Mar 13, 2024 - - - -
- - - - Thursday, Mar 14, 2024 - - - -
- - - - Friday, Mar 15, 2024 - - - -
CUNY Graduate Center
Friday, March 15, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Squares, ultrafilters and forcing axioms
A uniform ultrafilter over a cardinal is called indecomposable if, whenever and , there is a set such that is countable. Indecomposability is a natural weakening of -completeness and has a number of implications for, e.g., the structure of ultraproducts. In the 1980s, Sheard answered a question of Silver by proving the consistency of the existence of an inaccessible but not weakly compact cardinal carrying an indecomposable ultrafilter. Recently, however, Goldberg proved that this situation cannot hold above a strongly compact cardinal: If is strongly compact and carries an indecomposable ultrafilter, then is either measurable or a singular limit of countably many measurable cardinals. We prove that the same conclusion follows from the Proper Forcing Axiom, thus adding to the long list of statements first shown to hold above a strongly compact or supercompact cardinal and later shown also to follow from PFA. Time permitting, we will employ certain indexed square principles to prove that our results are sharp. This is joint work with Assaf Rinot and Jing Zhang.
CUNY Graduate Center
Tennebaum's Theorem for quotient presentations and model-theoretic skepticism
A computable quotient presentation of a mathematical structure consists of a computable structure on the natural numbers , meaning that the operations and relations of the structure are computable, and an equivalence relation on , not necessarily computable but which is a congruence with respect to this structure, such that the quotient is isomorphic to the given structure . Thus, one may consider computable quotient presentations of graphs, groups, orders, rings and so on.
A natural question asked by B. Khoussainov in 2016, is if the Tennenbaum Thoerem extends to the context of computable presentations of nonstandard models of arithmetic. In a joint work with J.D. Hamkins we have proved that no nonstandard model of arithmetic admits a computable quotient presentation by a computably enumerable equivalence relation on the natural numbers.
However, as it happens, there exists a nonstandard model of arithmetic admitting a computable quotient presentation by a co-c.e. equivalence relation. Actually, there are infinitely many of those. The idea of the proof consists is simulating the Henkin construction via finite injury priority argument. What is quite surprising, the construction works (i.e. injury lemma holds) by Hilbert's Basis Theorem. The latter argument is joint work with T. Slaman and L. Harrington.
- - - - Monday, Mar 18, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, March 18, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Modal quantifiers, potential infinity, and Yablo sequences
Abstract: When properly arithmetized, Yablo’s paradox results in a set of formulas which (with local disquotation in the background) turns out to be consistent, but omega-inconsistent. Adding either uniform disquotation or the omega-rule results in inconsistency. Since the paradox involves an infinite sequence of sentences, one might think that it doesn’t arise in finitary contexts. We study whether it does. It turns out that the issue depends on how the finitistic approach is formalized. On one of them, proposed by Marcin Mostowski, all the paradoxical sentences simply fail to hold. This happens at a price: the underlying finitistic arithmetic itself is omega-inconsistent. Finally, when studied in the context of a finitistic approach which preserves the truth of standard arithmetic, the paradox strikes back — it does so with double force, for now the inconsistency can be obtained without the use of uniform disquotation or the omega-rule.
Note: This is joint work with Rafał Urbaniak (Gdańsk).
- - - - Tuesday, Mar 19, 2024 - - - -
- - - - Wednesday, Mar 20, 2024 - - - -
The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL: http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker: Sina Hazratpour, Johns Hopkins University.
Date and Time: Wednesday March 20, 2024, 7:00 - 8:30 PM.
Title: Fibred Categories in Lean.
Abstract: Fibred categories are one of the most important and useful concepts in category theory and its application in categorical logic. In this talk I present my recent formalization of fibred categories in the interactive theorem prover Lean 4. I begin by highlighting certain technical challenges associated with handling the equality of objects and functors within the extensional dependent type system of Lean, and how they can be overcome. In this direction, I will demonstrate how we can take advantage of dependent coercion, instance synthesis, and automation tactics from the Lean toolbox. Finally I will discuss a formalization of Homotopy Type Theory in Lean 4 using a fired categorical framework.
- - - - Thursday, Mar 21, 2024 - - - -
- - - - Friday, Mar 22, 2024 - - - -
CUNY Graduate Center
Friday, March 22, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
Arthur Apter, CUNY
A choiceless answer to a question of Woodin
In a lecture presented in July 2023, Moti Gitik discussed the following question from the 1980s due to Woodin, as well as approaches to its solution and why it is so difficult to solve:
Question: Assuming there is no inner model of ZFC with a strong cardinal, is it possible to have a model of ZFC such that ' and for every ', together with the existence of an inner model of ZFC such that for the so that and ' is measurable and '?I will discuss how to find answers to this question, if we drop the requirement that satisfies the Axiom of Choice. I will also briefly discuss the phenomenon that on occasion, when the Axiom of Choice is removed from consideration, a technically challenging question or problem becomes more tractable. One may, however, end up with models satisfying conclusions that are impossible in ZFC.
Reference: A. Apter, 'A Note on a Question of Woodin', Bulletin of the Polish Academy of Sciences (Mathematics), volume 71(2), 2023, 115--121.
CUNY Graduate Center
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
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KGRC Talks - March 11-15
Set theory and topology seminar 12.03.2024 Grigor Sargsyan
Grigor Sargsyan (IMPAN)
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
Wednesday seminar
KGRC Set Theory Talks - March 4-8
Alexi Block Gorman, Ohio State University, Columbus, US (host: Matthias Aschenbrenner) visits March 3–9
Elliot Kaplan, McMaster University, Hamilton, CA, Columbus, US (host: Nigel Pynn-Coates) visits March 3–9
Silvan Horvath, ETH Zurich, CH (host: Vera Fischer) visits March 4–July 31
* * * * * * * * *
KGRC/Institute of Mathematics invites you to the following talks:
(updates at https://kgrc.univie.ac.at/) )
SET THEORY SEMINAR
Kolingasse 14–16, 1090, 1st floor, SR 10,
Thursday, March 7, 11:30am – 12:00pm, hybrid mode
”Magic Sets”
S. Horvath (ETH Zurich, CH)
A Magic Set is a set M of reals with the property that for all nowhere constant, continuous functions f and
g on the reals it holds that f [M ] ⊆ g[M ] implies f = g.
I will cover some of the basic results on magic sets and introduce magic forcing - a forcing notion that adds
a new magic set to the ground model.
Zoom: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at.
Meeting ID: 671 1734 6051
Passcode: kgrc
Please direct any questions about this talk to vera.fischer@univie.ac.at.
* * * * * * * * *
SET THEORY SEMINAR
Kolingasse 14–16, 1090, 1st floor, SR 10,
Thursday, March 7, 12:00pm – 13:00pm, hybrid mode
”A general theory of iterated forcing using finitely additive measures”
A. F. Uribe Zapata (TU Wien)
Saharon Shelah in 2000 introduced a finite-support iteration using finitely additive measures to prove that,
consistently, the covering of the null ideal may have countable cofinality. In 2019, Jakob Kellner, Saharon
Shelah, and Anda R. T ̆anasie achieved some new results and applications using such iterations.
In this talk, based on the works mentioned above, we present a general theory of iterated forcing using
finitely additive measures, which was developed in the speaker’s master’s thesis. For this purpose, we intro-
duce two new notions: on the one hand, we define a new linkedness property, which we call ”FAM-linked”
and, on the other hand, we generalize the idea of intersection number to forcing notions, which justifies the
limit steps of our iteration theory. Finally, we show a new separation of the left-side of Cicho ́n’s diagram
allowing a singular value.
Zoom info
Zoom: If you have not received the Zoom data by the day before the talk, please contact petra.czarnecki@univie.ac.at.
Passcode: kgrc
Please direct any questions about this talk to vera.fischer@univie.ac.at.
* * * * * * * * *
VIDEO recordings available so far of the LOGIC COLLOQUIUM:
January 25: Y. Khomskii (Amsterdam U College, NL and U Hamburg, DE) "Trees, Transcendence and Quasi-generic reals"https://ucloud.univie.ac.at/index.php/s/Wd9DPzXqQsnBPzC
November 16: D. A. Mejía (Shizuoka U, JP) ”Iterations with ultrafilter-limits and fam-limits” https://ucloud.univie.ac.at/index.php/s/T6pD2XgwTfNPYtn
—–
The LECTURE NOTE for Diego Mejía’s mini-course available so far of the Set Theory Seminar:
January 25: D. A. Mejıa (Shizuoka U, JP) ”Forcing techniques for Cicho ́n’s Maximum” https://mathematik.univie.ac.at/fileadmin/user_upload/f_mathematik/Events_News/Vortraege_Events/2023-24/20240122_Mejia_minicourse-1.pdf.
VIDEO recordings available so far of the SET THEORY SEMINAR:
January 25: D. A. Mejía (Shizuoka U, JP), ”Forcing techniques for Cicho ́n’s Maximum VI” video: https://ucloud.univie.ac.at/index.php/s/8EyKfLZW3NBH4f2
January 18: D. A. Mejía (Shizuoka U, JP), ”Forcing techniques for Cicho ́n’s Maximum V” video:https://ucloud.univie.ac.at/index.php/s/QrKjY6CYtJMx7WT
January 11: D. A. Mejía (Shizuoka U, JP), ”Forcing techniques for Cicho ́n’s Maximum IV” https://ucloud.univie.ac.at/index.php/s/KFpbqsLjQm3tcKn
December 7: "Forcing techniques for Cichoń's Maximum: FS iterations II" video:https://ucloud.univie.ac.at/index.php/s/iwqKFiYCEpPaPsN
November 30: "Forcing techniques for Cichoń's Maximum I" video: https://ucloud.univie.ac.at/index.php/s/xWjSe9eA92ReRV9
-- Mag. Petra Czarnecki de Czarnce-Chalupa Institute of Mathematics (Kurt Goedel Research Center, Logic) University of Vienna Kolingasse 14-16, #7.48 1090 Vienna, Austria Phone: +43/ (0)1 4277-50501
NUS Logic Seminar Talk by Rupert Hoelzl on 6 March 2024 17:00 hrs
Set theory and topology seminar 5.03.2024 Agnieszka Widz
Agnieszka Widz
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday, March 4, 3:30pm, Rutgers University, Hill 705
Logic and Metaphysics Workshop
Date: Monday, March 4, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Elise Crull (CUNY).
Title: Declaring no dependence
Abstract: Viable fundamental ontologies require at least one suitably stable, generic-yet-toothy metaphysical dependence relation to establish fundamentality. In this talk I argue that recent experiments in quantum physics using Page-Wootters devices to model global vs. local dynamics cast serious doubt on the existence of such metaphysical dependence relations when – and arguably, inevitably within any ontological framework – physical systems serve as the relata.
- - - - Tuesday, Mar 5, 2024 - - - -
Tightness and solidity in fragments of Peano Arithmetic
It was shown by Visser that Peano Arithmetic has the property that no two distinct extensions of it (in its language) are bi-interpretable. Enayat proposed to refer to this property of a theory as tightness and to carry out a more systematic study of tightness and its stronger variants, which he called neatness and solidity.
Enayat proved that not only , but also , , and are solid; and on the other hand, that finitely axiomatisable fragments of them are not even tight. Later work by a number of authors showed that many natural proper fragments of these theories are also not tight.
Enayat asked whether there are proper solid subtheories (containing some basic axioms that depend on the theory) of the theories listed above. We answer this question in the case of by proving that for every there exists a solid theory strictly between and . Furthermore, we can require that the theory does not interpret , and that if any true arithmetic sentence is added to it, the theory still does not prove .
Joint work with Leszek Kołodziejczyk and Mateusz Łełyk.
Spring 2024 (online) For a zoom link contact S.Artemov
Tuesday, March 5, Time 2:00 - 4:00 PM
Speaker: Sergei Artemov, Graduate Center
Title: On Tolerance Analysis in Extensive-Form Games.
- - - - Wednesday, Mar 6, 2024 - - - -
The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL: http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker: Jean-Pierre Marquis, Universite de Montreal.
Date and Time: Wednesday March 6, 2024, 7:00 - 8:30 PM. IN PERSON TALK!
Title: Hom sweet Hom: a sketch of the history of duality in category theory.
Abstract: Duality, in its various forms and roles, played a surprisingly important part in the development of category theory. In this talk, I will concentrate on the development of these forms and roles that lead to the categorical formulation of Stone-type dualities in the 1970s. I will emphasize the epistemological gain and loss along the way.
- - - - Thursday, Mar 7, 2024 - - - -
- - - - Friday, Mar 8, 2024 - - - -
CUNY Graduate Center
Friday, March 8, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
- - - - Monday, Mar 11, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, March 11, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Dispensing with the grounds of logical necessity
Abstract: Logical laws are typically conceived as being necessary. But in virtue of what is this the case? That is, what are the grounds of logical necessity? In this paper, I examine four different answers to this question in terms of: truth-conditions, invariance of truth-values under different interpretations, possible worlds, and brute facts. I ultimately find all of them wanting. I conclude that an alternative conception of logic that dispenses altogether with grounds of logical necessity provides a less troublesome alternative. I then indicate some of the central features of this conception.
- - - - Tuesday, Mar 12, 2024 - - - -
Albert Visser, Utrecht University
Restricted completions
This talk reports on research in collaboration with Ali Enayat and Mateusz Łełyk.
Steffen Lempp and Dino Rossegger asked: is there a consistent completion of that is axiomatised by sentences of bounded quantifier-alternation complexity? We show that there is no such restricted completion. We also show that, if one changes the measure of complexity to being , there is a restricted completion. Specifically, we show that the true theory of the non-negative part of can be axiomatised by a single sentence plus a set of -sentences.In our talk we will sketch these two answers. One of our aims is to make clear is that the negative answer for the case of quantifier-alternation complexity simply follows from Rosser's Theorem viewed from a sufficiently abstract standpoint.
- - - - Wednesday, Mar 13, 2024 - - - -
- - - - Thursday, Mar 14, 2024 - - - -
- - - - Friday, Mar 15, 2024 - - - -
CUNY Graduate Center
Friday, March 15, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
CUNY Graduate Center
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
-------- ADMINISTRIVIA --------
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Wednesday seminar
Wednesday seminar
45th Nankai Logic Colloquium
Hello everyone,
Our speaker this week will be Takayuki Kihara from Nagoya University. This talk is going to take place this Friday, Mar. 01, from 4pm to 5pm(UTC+8, Beijing time).
[Title]
On the Wadge degrees of Borel partitions
[Abstract]
In descriptive set theory, there are a lot of semi-well-ordered hierarchies, such as the Borel hierarchy, the projective hierarchy, and the difference hierarchy. Under AD, their ultimate refinement is provided by the Wadge degrees, which is also semi-well-ordered.
Now, the question arises: what exactly gives rise to this semi-well-ordered structure?
Our goal is to reveal the true structure behind this semi-well-order. To achieve this, it is crucial to handle not subsets (two-valued functions) but partitions (k-valued functions). As long as we only observe two-valued functions, all dynamic mechanisms lurking behind collapse, appearing to our eyes only as a semi-well-order. By dealing with partitions, we can expose the ultimate dynamic structure that was concealed. What existed there is not a semi-well-order but rather a better quasi-order, -- a sort of transfinite "matryoshkas" of trees.
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best Wishes,
Ming Xiao
Cross-Alps Logic Seminar (speaker: Simon Henry)
This Week in Logic at CUNY
Logic and Metaphysics Workshop
Date: Monday, Feb 26, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Matteo Plebani (Turin).
Title: Semantic paradoxes as collective tragedies
Abstract: What does it mean to solve a paradox? A common assumption is that to solve a paradox we need to find the wrong step in a certain piece of reasoning. In this talk, I will argue while in the case of some paradoxes such an assumption might be correct, in the case of paradoxes such as the liar and Curry’s paradox it can be questioned.
- - - - Tuesday, Feb 27, 2024 - - - -
Computational Logic Seminar
Spring 2024 (online)
Tuesday, February 27, 2:00 - 4:00 PM
For a ZOOM link contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Vincent Peluce, Graduate Center
Title: What is Intuitionistic Arithmetic
- - - - Wednesday, Feb 28, 2024 - - - -
The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL: http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
- - - - Thursday, Feb 29, 2024 - - - -
- - - - Friday, Mar 1, 2024 - - - -
CUNY Graduate Center
Rehana Patel Wesleyan University
CUNY Graduate Center
Alf Dolich, CUNY
Component Closed Structures on the Reals
A structure, R, expanding is called component closed if whenever is definable so are all of 's connected components. Two basic examples of component closed structures are and . It turns out that these two structures are exemplary of a general phenomenon for component closed structures from a broad class of expansions of : either their definable sets are very 'tame' (as in the case of the real closed field) or they are quite 'wild' (as in the case of the real field expanded by the integers).
- - - - Monday, Mar 4, 2024 - - - -
Rutgers Logic Seminar
Monday, March 4, 3:30pm, Rutgers University, Hill 705
Logic and Metaphysics Workshop
Date: Monday, March 4, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Elise Crull (CUNY).
Title: Declaring no dependence
Abstract: Viable fundamental ontologies require at least one suitably stable, generic-yet-toothy metaphysical dependence relation to establish fundamentality. In this talk I argue that recent experiments in quantum physics using Page-Wootters devices to model global vs. local dynamics cast serious doubt on the existence of such metaphysical dependence relations when – and arguably, inevitably within any ontological framework – physical systems serve as the relata.
- - - - Tuesday, Mar 5, 2024 - - - -
- - - - Wednesday, Mar 6, 2024 - - - -
The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL: http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker: Jean-Pierre Marquis, Universite de Montreal.
Date and Time: Wednesday March 6, 2024, 7:00 - 8:30 PM. IN PERSON TALK!
Title: Hom sweet Hom: a sketch of the history of duality in category theory.
Abstract: Duality, in its various forms and roles, played a surprisingly important part in the development of category theory. In this talk, I will concentrate on the development of these forms and roles that lead to the categorical formulation of Stone-type dualities in the 1970s. I will emphasize the epistemological gain and loss along the way.
- - - - Thursday, Mar 7, 2024 - - - -
- - - - Friday, Mar 8, 2024 - - - -
CUNY Graduate Center
Friday, March 8, 12:30pm NY time
Virtual: Please email Victoria Gitman (vgitman@gmail.com) for meeting id.
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
-------- ADMINISTRIVIA --------
To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.
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Wednesday seminar
44th Nankai Logic Colloquium
Hello everyone,
Our speaker this week will be Clark Lyons from the University of California, Los Angeles. This talk is going to take place this Friday, Feb 23, from 9am to 10am(UTC+8, Beijing time).
Title: Baire Measurable Matchings in Non-amenable Graphs Abstract: Tutte's theorem provides a necessary and sufficient condition for a finite graph to have a perfect matching. In this talk I will present joint work with Kastner showing that if a locally finite Borel graph satisfies a strengthened form of Tutte's condition, then it has a perfect matching which is Baire measurable. As a consequence, the Schreier graph of a free action of a non-amenable group on a Polish space admits a Baire measurable perfect matching. This is analogous to the result of Csoka and Lippner on factor of IID perfect matchings for non-amenable Cayley graphs.
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best Wishes,
Ming Xiao
Set theory and topology seminar 27.02.2024 Grzegorz Plebanek
Grzegorz Plebanek
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
Wednesday seminar
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday, Feb 19, 3:30pm, Rutgers University, Hill 705
Artem Chernikov, Maryland
Intersecting sets in probability spaces and Shelah's classification
- - - - Tuesday, Feb 20, 2024 - - - -
Spring 2024 (online)
Title: Counterpossibles in relative computability theory: a closer look
HT If the validity problem were algorithmically solvable, then arithmetical truth would be also algorithmically decidable
As Jenny himself emphasizes, establishing that HT is a false counterpossible would be highly significant. According to the standard analysis of counterfactuals ([Lewis, 1973], [Stalnaker, 1968]) all counterpossibles are vacuously true. If HT is false, then, the standard analysis of counterfactuals is wrong.
In this paper, we will argue that HT admits two readings, which are expressed by two different ways of formalizing HT. Under the first reading, HT is clearly a counterpossible. Under the second reading, HT is clearly false. Hence, it is possible to read HT as a counterpossible (section 2) and it is possible to read HT as a false claim (section 3). However, it is unclear that it is possible to do both things at once, i.e. interpret HT as a false counterpossible.
It can be proven that the two readings are not equivalent. The formalization expressing the first reading is a mathematical theorem, which means that under the first reading, HT is a true counterpossible. On the other hand, I will argue that under the second reading HT, while false, is best interpreted as a counterpossible with a contingent antecedent.
- - - - Wednesday, Feb 21, 2024 - - - -
- - - - Thursday, Feb 22, 2024 - - - -
- - - - Friday, Feb 23, 2024 - - - -
CUNY Graduate Center
- - - - Monday, Feb 26, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, Feb 26, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Matteo Plebani (Turin).
Title: Semantic paradoxes as collective tragedies
Abstract: What does it mean to solve a paradox? A common assumption is that to solve a paradox we need to find the wrong step in a certain piece of reasoning. In this talk, I will argue while in the case of some paradoxes such an assumption might be correct, in the case of paradoxes such as the liar and Curry’s paradox it can be questioned.
- - - - Tuesday, Feb 27, 2024 - - - -
- - - - Wednesday, Feb 28, 2024 - - - -
The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL: http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
In this talk, we will construct semi-simplicial types in Displayed Type Theory [dTT], a fully semantically general homotopy type theory. Many of our main results are independent of type theory and will say something new and surprising about the homotopy theoretic notion of a classifier for semi-simplicial objects.
This talk is based on joint work with Michael Shulman. Reference: https://arxiv.org/abs/2311.18781
- - - - Thursday, Feb 29, 2024 - - - -
- - - - Friday, Mar 1, 2024 - - - -
CUNY Graduate Center
Rehana Patel Wesleyan University
CUNY Graduate Center
Alf Dolich, CUNY
Component Closed Structures on the Reals
A structure, R, expanding is called component closed if whenever is definable so are all of 's connected components. Two basic examples of component closed structures are and . It turns out that these two structures are exemplary of a general phenomenon for component closed structures from a broad class of expansions of : either their definable sets are very 'tame' (as in the case of the real closed field) or they are quite 'wild' (as in the case of the real field expanded by the integers).
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
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Logic Seminar Wed 21.02.2024 17:00 hrs at NUS by Neil Barton
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday, Feb 12, 3:30pm, Rutgers University, Hill 705
For a cardinal $\kappa\ge 2$, one can weaken the classical concept "x is ordinal definable" (i.e., x is the unique object satisfying some condition involving ordinal parameters) to "x is <$\kappa$-blurrily ordinal definable," meaning that x is one of fewer than $\kappa$ many objects satisfying some condition involving ordinal parameters. By considering the hereditary version of this, one naturally arrives at the inner model <$\kappa$-HOD, the class of all hereditarily <$\kappa$-blurrily ordinal definable sets. In ZFC, by varying $\kappa$, one obtains a hierarchy of inner models spanning the entire spectrum from HOD to V. Those stages in the hierarchy where something new is added I call leaps.
I will give an overview of what is known about this hierarchy: ZFC-provable facts regarding the relationships between the stages of the hierarchy and the basic structure of leaps, and consistency results on leap constellations, including consistency strength determinations.
- - - - Tuesday, Feb 13, 2024 - - - -
MOPA
The Borel hierarchy gives a robust way to stratify the complexity of sets of countable structures and is intimately tied with definability in infinitary logic via the Lopez-Escobar theorem. However, what happens with sets axiomatizable in finitary first-order logic, such as the set of structures satisfying a given finitary first-order theory T? Is the complexity of the set of T's models in any way related to the quantifier complexity of the sentences axiomatizing it? In particular, if a theory T is not axiomatizable by a set of sentences of bounded quantifier complexity, can the set of models of T still be at a finite level of the Borel hierarchy?
In this talk, we will present results concerning these questions:
In joint work with Andrews, Gonzalez, Lempp, and Zhu we show that the set of models of a theory T is -complete if and only if T does not have an axiomatization by sentences of bounded quantifier complexity, answering the last question in the negative. We also characterize the Borel complexity of the set of models of complete theories in terms of their finitary axiomatizations. Our results suggest that infinitary logic does not provide any efficacy when defining first-order properties, a phenomenon already observed by Wadge and Keisler and, recently, rediscovered by Harrison-Trainor and Kretschmer using different techniques.
Combining our results with recent results by Enayat and Visser, we obtain that a large class of theories studied in the foundations of mathematics, sequential theories, have a maximal complicated set of models.
Spring 2024 (online)
- - - - Wednesday, Feb 14, 2024 - - - -
- - - - Thursday, Feb 15, 2024 - - - -
- - - - Friday, Feb 16, 2024 - - - -
Largeness notions
Finite Ramsey Theorem states that fixed , there exists such that for each coloring of with colors, there is a homogeneous subset of of cardinality at least . Starting with the celebrated Paris-Harrington theorem, many Ramsey-like results have been studied using different largeness notions rather than the cardinality. I will introduce the largeness notion defined by Ketonen and Solovay based on fundamental sequences of ordinals. Then I will describe an alternative and more flexible largeness notion using blocks and barriers. If time allows, I will talk about how the latter can be used to study a more general Ramsey-like result.
CUNY Graduate Center
The Ginsburg-Sands theorem and computability
In their 1979 paper `Minimal Infinite Topological Spaces,’ Ginsburg and Sands proved that every infinite topological space has an infinite subspace homeomorphic to exactly one of the following five topologies on : indiscrete, discrete, initial segment, final segment, and cofinite. The proof, while nonconstructive, features an interesting application of Ramsey's theorem for pairs (). We analyze this principle in computability theory and reverse mathematics, using Dorais's formalization of CSC spaces. Among our results are that the Ginsburg-Sands theorem for CSC spaces is equivalent to while for Hausdorff spaces it is provable in . Furthermore, if we enrich a CSC space by adding the closure operator on points, then the Ginsburg-Sands theorem turns out to be equivalent to the Chain-Antichain Principle (). The most surprising case is that of the Ginsburg-Sands theorem restricted to spaces. Here, we show that the principle lies strictly between and , yielding perhaps the first natural theorem of ordinary mathematics (i.e., conceived outside of logic) to occupy this interval. I will discuss the proofs of both the implications and separations, which feature several novel combinatorial elements, and survey a new class of purely combinatorial principles below and not implied by revealed by our investigation. This is joint work with Heidi Benham, Andrew DeLapo, Reed Solomon, and Java Darleen Villano.
- - - - Monday, Feb 19, 2024 - - - -
- - - - Tuesday, Feb 20, 2024 - - - -
- - - - Wednesday, Feb 21, 2024 - - - -
- - - - Thursday, Feb 22, 2024 - - - -
- - - - Friday, Feb 23, 2024 - - - -
CUNY Graduate Center
WHERE: Rutgers, The State University of New Jersey.
WHEN: Saturday, March 23
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
-------- ADMINISTRIVIA --------
To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.
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Wednesday seminar
Logic Seminar Talk 7 February 2024 17:00 hrs by Alexander Rabinovich at NUS
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday, Feb 5, 3:30pm, Rutgers University, Hill 705
Filippo Calderoni, Rutgers
The L-space conjecture and descriptive set theory
Logic and Metaphysics Workshop
Date: Monday, Feb 5, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Some model theory for axiomatic theories of truth
Abstract: Tarski’s arithmetic is the complete theory of (N,+,x,Tr), where (N,+,x) is the standard model of arithmetic and Tr is the set of Gödel numbers of all true arithmetic sentences. An axiomatic theory of truth is an axiomatic subtheory of Tarski’s arithmetic. If (M,+,x,T) is a model of an axiomatic theory of truth, then we call T a truth class. In 1981, Kotlarski, Krajewski, and Lachlan proved that every completion of Peano’s arithmetic has a model that is expandable to a model with a truth class T that satisfies all biconditionals in Tarski’s definition of truth formalized in PA. If T is such a truth class, it assigns truth values to all sentences in the sense of M, standard and nonstandard. The proof showed that such truth classes can be quite pathological. For example, they may declare true some infinite disjunctions of the single sentence (0=1). In 2018, Enayat and Visser gave a much simplified model-theoretic proof, which opened the door for further investigations of nonstandard truths, and many interesting new results by many authors appeared. I will survey some of them, concentrating on their model-theoretic content.
- - - - Tuesday, Feb 6, 2024 - - - -
- - - - Wednesday, Feb 7, 2024 - - - -
The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL: http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker: Saeed Salehi, Univeristy of Tarbiz.
Date and Time: Wednesday February 7, 2024, 11:00AM - 12:00 NOON. NOTICE SPECIAL TIME!!! ZOOM TALK!!! (see website for zoom link)
Title: On Chaitin's two HP's: (1) Heuristic Principle and (2) Halting Probability.
Abstract: Two important achievements of Chaitin will be investigated: the Omega number, which is claimed to be the halting probability of input-free programs, and the heuristic principle, which is claimed to hold for program-size complexity. Chaitin's heuristic principle says that the theories cannot prove the heavier sentences; the sentences and the theories were supposedly weighed by various computational complexities, which all turned out to be wrong or incomplete. In this talk, we will introduce a weighting that is not based on any computational complexity but on the provability power of the theories, for which Chaitin's heuristic principle holds true. Also, we will show that the Omega number is not equal to the halting probability of the input-free programs and will suggest some methods for calculating this probability, if any.
- - - - Thursday, Feb 8, 2024 - - - -
- - - - Friday, Feb 9, 2024 - - - -
Speaker: Emma Dinowitz, Grad Center
CUNY Graduate Center
Friday, Feb 9, 12:30pm NY time, Room: 6494
Tukey-top ultrafilters under UA
In the first part of the talk, we will provide some background and motivation to study the Glavin property. In particular, we will present a recently discovered connection between the Galvin property and the Tukey order on ultrafilters. This is a joint result with Natasha Dobrinen. In the second part, we will introduce several diamond-like principles for ultrafilters, and prove some relations with the Galvin property. Finally, we use the Ultrapower Axiom to characterize the Galvin property in the known canonical inner models. The second and third part is joint work with Gabriel Goldberg.
CUNY Graduate Center
Properties of Generic Algebraic Fields
The algebraic field extensions of the rational numbers – equivalently, the subfields of the algebraic closure – naturally form a topological space homeomorphic to Cantor space. Consequently, one can speak of 'large' collections of such fields, in the sense of Baire category: collections that are comeager in the space. Under a standard definition, the 1-generic fields form a comeager set in this space. Therefore, one may think of a property common to all 1-generic fields as a property that one might reasonably expect to be true of an arbitrarily chosen algebraic field.
We will present joint work with Eisenträger, Springer, and Westrick that proves several intriguing properties to be true of all 1-generic fields . First, in every such , both the subring of the integers and the subring of the algebraic integers of cannot be defined within by an existential formula, nor by a universal formula. (Subsequent work by Dittman and Fehm has shown that in fact these subrings are completely undefinable in these fields.) Next, for every presentation of every such , the root set
is always of low Turing degree relative to that presentation, but is essentially always undecidable relative to the presentation. Moreover, the set known as Hilbert's Tenth Problem for ,
is exactly as difficult as , which is its restriction to single-variable polynomials. Finally, even the question of having infinitely many solutions,
is only as difficult as . These results are proven by using a forcing notion on the fields and showing that it is decidable whether or not a given condition forces a given polynomial to have a root, or to have infinitely many roots.
- - - - Monday, Feb 12, 2024 - - - -
Rutgers Logic Seminar
Monday, Feb 12, 3:30pm, Rutgers University, Hill 705
- - - - Tuesday, Feb 13, 2024 - - - -
MOPA
The Borel hierarchy gives a robust way to stratify the complexity of sets of countable structures and is intimately tied with definability in infinitary logic via the Lopez-Escobar theorem. However, what happens with sets axiomatizable in finitary first-order logic, such as the set of structures satisfying a given finitary first-order theory T? Is the complexity of the set of T's models in any way related to the quantifier complexity of the sentences axiomatizing it? In particular, if a theory T is not axiomatizable by a set of sentences of bounded quantifier complexity, can the set of models of T still be at a finite level of the Borel hierarchy?
In this talk, we will present results concerning these questions:
In joint work with Andrews, Gonzalez, Lempp, and Zhu we show that the set of models of a theory T is -complete if and only if T does not have an axiomatization by sentences of bounded quantifier complexity, answering the last question in the negative. We also characterize the Borel complexity of the set of models of complete theories in terms of their finitary axiomatizations. Our results suggest that infinitary logic does not provide any efficacy when defining first-order properties, a phenomenon already observed by Wadge and Keisler and, recently, rediscovered by Harrison-Trainor and Kretschmer using different techniques.
Combining our results with recent results by Enayat and Visser, we obtain that a large class of theories studied in the foundations of mathematics, sequential theories, have a maximal complicated set of models.
- - - - Wednesday, Feb 14, 2024 - - - -
- - - - Thursday, Feb 15, 2024 - - - -
- - - - Friday, Feb 16, 2024 - - - -
Largeness notions
Finite Ramsey Theorem states that fixed , there exists such that for each coloring of with colors, there is a homogeneous subset of of cardinality at least . Starting with the celebrated Paris-Harrington theorem, many Ramsey-like results have been studied using different largeness notions rather than the cardinality. I will introduce the largeness notion defined by Ketonen and Solovay based on fundamental sequences of ordinals. Then I will describe an alternative and more flexible largeness notion using blocks and barriers. If time allows, I will talk about how the latter can be used to study a more general Ramsey-like result.
CUNY Graduate Center
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
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Wednesday seminar
This Week in Logic at CUNY
Rutgers Logic Seminar
Monday, Jan 29, 3:30pm, Rutgers University, Hill 705
Jenna Zomback, Maryland
Boundary actions of free semigroups
- - - - Tuesday, Jan 30, 2024 - - - -
- - - - Wednesday, Jan 31, 2024 - - - -
- - - - Thursday, Feb 1, 2024 - - - -
- - - - Friday, Feb 2, 2024 - - - -
CUNY Graduate Center
Friday, Feb 2, 12:30pm NY time, Room: 6494
CUNY Graduate Center
- - - - Monday, Feb 5, 2024 - - - -
Logic and Metaphysics Workshop
Date: Monday, Feb 5, 4.15-6.15pm (NY time)
Room: Graduate Center Room 7395
Title: Some model theory for axiomatic theories of truth
Abstract: Tarski’s arithmetic is the complete theory of (N,+,x,Tr), where (N,+,x) is the standard model of arithmetic and Tr is the set of Gödel numbers of all true arithmetic sentences. An axiomatic theory of truth is an axiomatic subtheory of Tarski’s arithmetic. If (M,+,x,T) is a model of an axiomatic theory of truth, then we call T a truth class. In 1981, Kotlarski, Krajewski, and Lachlan proved that every completion of Peano’s arithmetic has a model that is expandable to a model with a truth class T that satisfies all biconditionals in Tarski’s definition of truth formalized in PA. If T is such a truth class, it assigns truth values to all sentences in the sense of M, standard and nonstandard. The proof showed that such truth classes can be quite pathological. For example, they may declare true some infinite disjunctions of the single sentence (0=1). In 2018, Enayat and Visser gave a much simplified model-theoretic proof, which opened the door for further investigations of nonstandard truths, and many interesting new results by many authors appeared. I will survey some of them, concentrating on their model-theoretic content.
- - - - Tuesday, Feb 6, 2024 - - - -
- - - - Wednesday, Feb 7, 2024 - - - -
The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
URL: http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker: Saeed Salehi, Univeristy of Tarbiz.
Date and Time: Wednesday February 7, 2024, 11:00AM - 12:00 NOON. NOTICE SPECIAL TIME!!! ZOOM TALK!!! (see website for zoom link)
Title: On Chaitin's two HP's: (1) Heuristic Principle and (2) Halting Probability.
Abstract: Two important achievements of Chaitin will be investigated: the Omega number, which is claimed to be the halting probability of input-free programs, and the heuristic principle, which is claimed to hold for program-size complexity. Chaitin's heuristic principle says that the theories cannot prove the heavier sentences; the sentences and the theories were supposedly weighed by various computational complexities, which all turned out to be wrong or incomplete. In this talk, we will introduce a weighting that is not based on any computational complexity but on the provability power of the theories, for which Chaitin's heuristic principle holds true. Also, we will show that the Omega number is not equal to the halting probability of the input-free programs and will suggest some methods for calculating this probability, if any.
- - - - Thursday, Feb 8, 2024 - - - -
- - - - Friday, Feb 9, 2024 - - - -
CUNY Graduate Center
Friday, Feb 9, 12:30pm NY time, Room: 6494
CUNY Graduate Center
Find us on the web at: nylogic.github.io
(site designed, built & maintained by Victoria Gitman)
-------- ADMINISTRIVIA --------
To subscribe/unsubscribe to this list, please email your request to jreitz@citytech.cuny.edu.
If you have a logic-related event that you would like included in future mailings, please email jreitz@citytech.cuny.edu.
43rd Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the morning.
Our speaker this week will be Alexander S. Kechris from the California Institute of Technology. This talk is going to take place this Friday, Jan 26, from 9am to 10am(UTC+8, Beijing time).
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best Wishes,
Ming Xiao
7th Workshop on Generalised Baire Spaces
Invitation to Logic Seminar 31 January 2024 17:00 hrs at NUS by Yu Liang
This Week in Logic at CUNY
- - - - Monday, Jan 22, 2024 - - - -
Rutgers Logic Seminar
Monday, Dec 11, 3:30pm, Rutgers University, Hill 705
Will Boney (Texas State)
- - - - Tuesday, Jan 23, 2024 - - - -
- - - - Wednesday, Jan 24, 2024 - - - -
- - - - Thursday, Jan 25, 2024 - - - -
- - - - Friday, Jan 26, 2024 - - - -
Memorial Lectures for Martin Davis
January 26, 2024
Courant Institute
All are welcome to attend this special event in memory of Professor Martin Davis.
There will be three lectures on his work from 1:00 - 2:30 pm, a memorial for Martin
and Virginia Davis from 2:45 - 3:45 pm, and a reception afterwards from 4-6 pm.
Preregistration is requested, ideally by January 15, using the website
https://cims.nyu.edu/dynamic/conferences/davis-memorial/
Next Week in Logic at CUNY:
- - - - Monday, Jan 29, 2024 - - - -
- - - - Tuesday, Jan 30, 2024 - - - -
- - - - Wednesday, Jan 31, 2024 - - - -
- - - - Thursday, Feb 1, 2024 - - - -
- - - - Friday, Feb 2, 2024 - - - -
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
Second Wrocław Logic Conference, Wrocław, 31 May to 2 Jun, 2024
Set Theory and Topology Seminar 23.01.2024 Łukasz Mazurkiewicz
Łukasz Mazurkiewicz
Abstract.
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
Urgent Announcement of Nankai Logic Colloquium: change to Voov (Tencent meeting)
Hello everyone,
Sorry, we have changed the meeting software to Voov (Tencent meeting) because the our Zoom account has been banned.
Please download Voov (Tencent meeting) from the following link:
https://voovmeeting.com/download-center.html?from=1002
the attachment is the Manual for using Voov (Tencent meeting)
Best Wishes,
Ming Xiao
Set Theory in the United Kingdom, London, February 15, 2024
42nd Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the afternoon.
Our speaker this week will be Gianluca Paolini from the University of Turin. This talk is going to take place this Friday, Jan 19, from 4pm to 5pm(UTC+8, Beijing time).
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best Wishes,
Ming Xiao
Cross-Alps Logic Seminar for World Logic Day (speaker: Charles Steinhorn)
On
Friday 19.01.2023 at 16:00
on
the occasion of World Logic Day 2024, a special session of the
Cross-Alps Logic Seminars will take place, with special guest
Charles
Steinhorn (Vassar College)
who
will give a talk on
O-minimality
as a framework for tame mathematical economics
Please
refer to the usual webpage of our LogicGroup for more
details and the abstract of the talk.
The
seminar will be held remotely through Webex. Please write to
vincenzo.dimonte [at] uniud [dot] it for the link to the event.
The
Cross-Alps Logic Seminar is co-organized by the logic groups of
Genoa, Lausanne, Turin and Udine as part of our collaboration in the
project PRIN 2022 'Models, sets and classification'.
Wednesday seminar
Logic Seminar at NUS Wed 17.01.2024 17:00 hrs by Tatsuta Makoto
41st Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the afternoon.
Our speaker this week will be Felipe Garcia-Ramos from Jagiellonian University. This talk is going to take place this Friday, Jan 12, from 4pm to 5pm(UTC+8, Beijing time).
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best Wishes,
Ming Xiao
KGRC Talks - January 8-12
set theory and topology seminar 9.01.2024 Piotr Borodulin-Nadzieja
Piotr Borodulin-Nadzieja
Abstract.
(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.
https://settheory.pwr.edu.pl/
http://www.math.uni.wroc.pl/seminarium/topologia
Wednesday seminar
40th Nankai Logic Colloquium
Hello everyone,
This week our weekly Nankai Logic Colloquium is going to be in the afternoon.
Our speaker this week will be Steve Jackson from the University of North Texas. This talk is going to take place this Friday, Jan 05, from 4pm to 5pm(UTC+8, Beijing time).
The records of past talks can be accessed at https://space.bilibili.com/253421893.
Best Wishes,
Ming Xiao