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* categories: The New York City Category Theory Seminar Fall 2023 line up of speakers.
@ 2023-09-05 22:15 Noson
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The New York City

Category Theory Seminar

Department of Computer Science <> 
Department of Mathematics <>  
The Graduate Center of The City University of New York

Time: Wednesdays 07:00 PM Eastern Time (US and Canada) 

365 Fifth Avenue (at 34th Street) map

(Diagonally across from the Empire State Building) 
New York, NY 10016-4309 
Room 6417 
The videos of the lectures will be put up on YouTube a few hours after the

Meeting ID: 832 4345 1066 
Passcode: NYCCTS1 

Seminar web page.
Videoed talks.
Previous semesters.
<> page.

Contact N. Yanofsky <>  to schedule a
or to add a name to the seminar mailing list. 



Fall 2023 





*  Speaker:     Tomáš Gonda, University of Innsbruck. 

*  Date and Time:     Wednesday September 27, 2023, 5:00 - 6:00 PM. ZOOM

*  Title:     A Framework for Universality in Physics, Computer Science, and

*  Abstract: Turing machines and spin models share a notion of universality
according to which some simulate all others. We set up a categorical
framework for universality which includes as instances universal Turing
machines, universal spin models, NP completeness, top of a preorder,
denseness of a subset, and others. By identifying necessary conditions for
universality, we show that universal spin models cannot be finite. We also
characterize when universality can be distinguished from a trivial one and
use it to show that universal Turing machines are non-trivial in this sense.
We leverage a Fixed Point Theorem inspired by a result of Lawvere to
establish that universality and negation give rise to unreachability (such
as uncomputability). As such, this work sets the basis for a unified
approach to universality and invites the study of further examples within
the framework. 



*  Speaker:     Thiago Alexandre, ???. 

*  Date and Time:     Wednesday October 11, 2023, 7:00 - 8:30 PM. 

*  Title:     ...derivator.... . 

*  Abstract: 



*  Speaker:     Michael Shulman, University of San Diego. 

*  Date and Time:     Wednesday October 18, 2023, 7:00 - 8:30 PM. 

*  Title:     The derivator of setoids. 

*  Abstract: 



*  Speaker:     Emilio Minichiello, CUNY Graduate Center. 

*  Date and Time:     Wednesday October 25, 2023, 7:00 - 8:30 PM. IN PERSON

*  Title:     A Mathematical Model of Package Management Systems. 

*  Abstract: In this talk, I will review some recent joint
<>  work with Gershom Bazerman and Raymond
Puzio. The motivation is simple: provide a mathematical model of package
management systems, such as the Hackage package respository for Haskell, or
Homebrew for Mac users. We introduce Dependency Structures with Choice (DSC)
which are sets equipped with a collection of possible dependency sets for
every element and satisfying some simple conditions motivated from real life
use cases. We define a notion of morphism of DSCs, and prove that the
resulting category of DSCs is equivalent to the category of antimatroids,
which are mathematical structures found in combinatorics and computer
science. We analyze this category, proving that it is finitely complete, has
coproducts and an initial object, but does not have all coequalizers.
Further, we construct a functor from a category of DSCs equipped with a
certain subclass of morphisms to the opposite of the category of finite
distributive lattices, making use of a simple finite characterization of the
Bruns-Lakser completion. 



*  Speaker:     Larry Moss, Indiana University, Bloomington . 

*  Date and Time:     Wednesday November 8, 2023, 7:00 - 8:30 PM. ZOOM TALK 

*  Title:     On Kripke, Vietoris, and Hausdorff Polynomial Functors. 

*  Abstract: The Vietoris space of compact subsets of a given Hausdorff
space yields an endofunctor V on the category of Hausdorff spaces. Vietoris
polynomial endofunctors on that category are built from V, the identity and
constant functors by forming products, coproducts and compositions. These
functors are known to have terminal coalgebras and we deduce that they also
have initial algebras. We present an analogous class of endofunctors on the
category of extended metric spaces, using in lieu of V the Hausdorff functor
H. We prove that the ensuing Hausdorff polynomial functors have terminal
coalgebras and initial algebras. Whereas the canonical constructions of
terminal coalgebras for Vietoris polynomial functors takes omega steps, one
needs \omega + \omega steps in general for Hausdorff ones. We also give a
new proof that the closed set functor on metric spaces has no fixed points. 



*  Speaker:     Pedro Sota, TBA. 

*  Date and Time:     Wednesday November 22, 2023, 7:00 - 8:30 PM. 

*  Title:     TBA. 

*  Abstract: 

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