The New York City
Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
TIME: Wednesdays 02:00-3:00 PM New York City Time.
PLACE: 365 Fifth Avenue (at 34th Street) map
(Diagonally across from the Empire State Building)
New York, NY 10016-4309
Room 4214.03.
If you cannot join us in person, please join us on Zoom. All talks are hybrid.
ZOOM INFORMATION:
https://brooklyn-cuny-edu.zoom.us/j/86376186975?pwd=50afg19K9jUacVc7ikNa6cY0vjkwtf.1
Meeting ID: 863 7618 6975
Passcode: NYCCTS
Seminar web page.
Videoed talks.
Previous semesters.
List of previous speakers.
Researchseminars.org page.
Co-organizers: Emilio Minichiello and Noson S. Yanofsky.
Contact E. Minichiello or N. Yanofsky to
schedule a speaker
or to add a name to the
seminar mailing list.
Fall 2026
Speaker: TBA, TBA.
Date and Time: Wednesday September 2, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
Abstract: TBA
Speaker: TBA, TBA.
Date and Time: Wednesday September 9, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
Abstract: TBA
Speaker: Sridhar Ramesh, TBA.
Date and Time: Wednesday September 23, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: Categorical structures for Gödel incompleteness and Löb’s theorem.
Abstract: A remarkably simple category-theoretic structure serves as an abstract environment for deriving Löb’s theorem, of which Gödel's incompleteness theorems are a special case. Specifically, an “introspective theory” is any category with finite limits T, with an internal category with finite limits C, along with a natural transformation from the self-indexing of T to C (construed as contravariant functors from T to the category of categories with finite limits). Amazingly, such minimal structure is in itself enough to derive Löb’s theorem as a guarded fixed point operation!
This abstraction (originally defined in the speaker's dissertation, on which this talk is based) unifies disparate contexts of Gödel-Löb phenomena, including traditional logic or arithmetic universes a la Joyal, along with the interpretation of guarded recursion for presheaves over well-founded orders by Birkedal et al, along with the distinct classical interpretation of the GL modal logic in well-founded transitive Kripke frames. We also explore the free introspective theory, which admits an explicit description ("the theory of geminal categories"), and discuss some illuminating relationships between introspective theories and geminal categories.
Speaker: Amar Hadzihasanovic, TBA.
Date and Time: Wednesday October 7, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: On the coherent self-dual omega-equivalence.
Abstract: The "walking equivalence" is the 2-category free on two morphisms going in opposite directions, together with 2-morphisms witnessing that those are each other's weak inverse. This 2-category is not coherent (which, in this case, means not contractible): a coherent replacement is the "walking adjoint equivalence", where the weak invertibility witnesses additionally satisfy the triangle equations.
The same problem appears for (naive) walking equivalences between higher categories, only worse because there is no obvious fix. Recently, I, Loubaton, Ozornova, and Rovelli constructed a coherent model of the walking equivalence of omega-categories, which, however, gives up one nice property: it is not self-dual with respect to the exchange of a morphism with its weak inverse. In this talk, I will present some recent work towards the construction of a coherent self-dual model, involving an operad arising in the combinatorics of noncrossing partitions.
Speaker: Emilio Minichiello, CUNY CityTech.
Date and Time: Wednesday October 21, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: Introduction to Locally Presentable Categories.
Abstract: This will be an expository talk about locally presentable categories. We will approach them in a very naive way, looking at what properties of the category of Sets we wish to generalize, and what we get from these properties. This talk will be taken from Appendix C in my notes.
Speaker: Raymond Puzio
Date and Time: Wednesday November 4, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
Abstract: TBA
Speaker: TBA, TBA.
Date and Time: Wednesday November 25, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: Jonathon Funk, Queensborough, CUNY.
Date and Time: Wednesday December 2, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
Abstract: TBA
Speaker: Krista Zehr, University of Albany.
Date and Time: Wednesday December 9, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
Abstract: TBA
Speaker: TBA, TBA.
Date and Time: Wednesday December 16, 2026, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Spring 2027
Speaker: TBA, TBA.
Date and Time: Wednesday February 3, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
Abstract: TBA
Speaker: TBA, TBA.
Date and Time: Wednesday February 10, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: TBA, TBA.
Date and Time: Wednesday February 24, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: TBA, TBA.
Date and Time: Wednesday March 3, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: TBA, TBA.
Date and Time: Wednesday March 17, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: TBA, TBA.
Date and Time: Wednesday April 7, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: TBA, TBA.
Date and Time: Wednesday April 14, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: TBA, TBA.
Date and Time: Wednesday May 5, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: TBA, TBA.
Date and Time: Wednesday May 12, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
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Speaker: TBA, TBA.
Date and Time: Wednesday May 19, 2027, 2:00 - 3:30 PM. NYC TIME.
Title: TBA.
Abstract: TBA