The New York City

Category Theory Seminar

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

THE TALKS WILL ALL BE DONE ON ZOOM THIS SEMESTER.
Time: Wednesdays 07:00 PM Eastern Time (US and Canada)
https://us02web.zoom.us/j/84134331639?pwd=TVRzVjlaZW5CNVh5ampxOGJ0RE5QQT09
Meeting ID: 841 3433 1639
Passcode: NYCCTS

Usually our talks take place at
365 Fifth Avenue (at 34th Street) map
(Diagonally across from the Empire State Building)
New York, NY 10016-4309
Room 6417
Wednesdays 7:00 - 8:30 PM

Videoed talks.
Previous semesters.
Research seminars page.

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




Fall 2021






  • Speaker:     Gemma De las Cuevas, University of Innsbruck.

  • Date and Time:     Wednesday October 6, 2021, 7:00 - 8:30 PM., on Zoom.

  • Title:     From simplicity to universality and undecidability.

  • Abstract: Why is it so easy to generate complexity? I will suggest that this is due to the phenomenon of universality — essentially every non-trivial system is universal, and thus able to explore all complexity in its domain. We understand universality in spin models, automata and neural networks. I will present the first step toward rigorously linking the first two, where we cast classical spin Hamiltonians as formal languages and classify the latter in the Chomsky hierarchy. We prove that the language of (effectively) zero-dimensional spin Hamiltonians is regular, one-dimensional spin Hamiltonians is deterministic context-free, and higher-dimensional and all-to-all spin Hamiltonians is context-sensitive. I will also talk about the other side of the coin of universality, namely undecidability, and will raise the question of whether universality is visible in Lawvere’s Theorem.

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  • Speaker:     Dan Shiebler, Oxford University.

  • Date and Time:     Wednesday October 20, 2021, 7:00 - 8:30 PM., on Zoom.

  • Title:     Out of Sample Generalization with Kan Extensions.

  • Abstract: A common problem in data science is use this function defined over this small set to generate predictions over that larger set. Extrapolation, interpolation, statistical inference and forecasting all reduce to this problem. The Kan extension is a powerful tool in category theory that generalizes this notion. In this work we explore several applications of Kan extensions to data science.

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  • Speaker:     Dusko Pavlovic, University of Hawai‘i at Mānoa.

  • Date and Time:     Wednesday November 3, 2021, 7:00 - 8:30 PM., on Zoom.

  • Title:     Geometry of computation and string-diagram programming in a monoidal computer.

  • Abstract: A monoidal computer is a monoidal category with a distinguished type carrying the structure of a single-instruction programming language. The instruction would be written as "run", but it is usually drawn as a string diagram. Equivalently, the monoidal computer structure can be viewed as a typed lambda-calculus without lambda abstraction, even implicit. Any Turing complete programming language, including Turing machines and partial recursive functions, gives rise to a monoidal computer. We have thus added yet another item to the Church-Turing list of models of computation. It differs from other models by its categoricity. While the other Church-Turing models can be programmed to simulate each other in many different ways, and each interprets even itself in infinitely many non-isomorphic ways, the structure of a monoidal computer is unique up to isomorphism. A monoidal category can be a monoidal computer in at most one way, just like it can be closed in at most one way, up to isomorphism. In other words, being a monoidal computer is a property, not structure. Computability is thus a categorical property, like completeness. This opens an alley towards an abstract treatment of parametrized complexity, one-way and trapdoor functions on one hand, and of algorithmic learning in the other.

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  • Speaker:     Marco Schorlemmer, Spanish National Research Council.

  • Date and Time:     Wednesday November 17, 2021, 7:00 - 8:30 PM., on Zoom.

  • Title:     TBA.

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  • Speaker:     Robert Geroch, University of Chicago.

  • Date and Time:     Wednesday December 1, 2021, 7:00 - 8:30 PM., on Zoom.

  • Title:     TBA.

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  • Speaker:     Samantha Jarvis, The CUNY Graduate Center.

  • Date and Time:     Wednesday December 15, 2021, 7:00 - 8:30 PM., on Zoom.

  • Title:     TBA.

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  • Speaker:     Todd Trimble, Western Connecticut State University.

  • Date and Time:     Wednesday December 22, 2021, 7:00 - 8:30 PM., on Zoom.

  • Title:     TBA.

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    Spring 2022








  • Speaker:     Ralph Wojtowicz, Shenandoah University.

  • Date and Time:     Wednesday February 2, 2022, 7:00 - 8:30 PM., on Zoom.

  • Title:     TBA.

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  • Speaker:     TBA, TBA.

  • Date and Time:     Wednesday February 16, 2022, 7:00 - 8:30 PM., on Zoom.

  • Title:     TBA.

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