You're reading the public-facing archive of the Category Theory Zulip server.
To join the server you need an invite. Anybody can get an invite by contacting Matteo Capucci at name dot surname at gmail dot com.
For all things related to this archive refer to the same person.
John Baez (Sep 16 2020 at 21:14):Here's another seminar series - they're having a seminar today:
Talks on are Wednesdays 7:00 - 8:30 PM Eastern Time. It seems to be run by Noson Yanofsky.
John Baez (Sep 16 2020 at 21:15):Date and Time: Wednesday September 16, 2020, 7:00 - 8:30 PM., on Zoom.
Speaker: Rick Jardine, University of Western Ontario.
Title: Posets, metric spaces, and topological data analysis.
John Baez (Sep 16 2020 at 21:15):Date and Time: Wednesday September 23, 2020, 7:00 - 8:30 PM., on Zoom.
Nothing yet.
John Baez (Sep 16 2020 at 21:16):Date and Time: Wednesday September 30, 2020, 7:00 - 8:30 PM., on Zoom.
Speaker: David Ellerman, University of Ljubljana.
Title: The Logical Theory of Canonical Maps: The Elements & Distinctions Analysis of the Morphisms, Duality, Canonicity, and Universal Constructions in Sets.
John Baez (Sep 16 2020 at 21:16):Date and Time: Wednesday October 7, 2020, 7:00 - 8:30 PM., on Zoom.
Nothing yet.
John Baez (Sep 16 2020 at 21:17):Date and Time: Wednesday October 14, 2020, 6:00 - 7:30PM (NOTICE DIFFERENT TIME) on Zoom.
Speaker: Jonathon Funk, Queensborough CUNY.
Title: Pseudogroup Torsors.
John Baez (Sep 16 2020 at 21:17):Date and Time: Wednesday October 21, 2020, 7:00 - 8:30 PM., on Zoom.
Speaker: Andrei V. Rodin, Saint Petersburg State University.
Title: ???
John Baez (Sep 16 2020 at 21:18):Date and Time: Wednesday October 28, 2020, 7:00 - 8:30 PM., on Zoom.
Speaker: Larry Moss, Indiana University.
Title: Coalgebra in Continuous Mathematics.
John Baez (Sep 16 2020 at 21:18):Date and Time: Wednesday November 4, 2020, 7:00 - 8:30 PM., on Zoom.
Speaker: Luis Scoccola, Michigan State University.
Title: Locally persistent categories and approximate homotopy theory.
John Baez (Sep 16 2020 at 21:19):Date and Time: Wednesday November 11, 2020, 7:00 - 8:30 PM., on Zoom.
Speaker: Noah Chrein, University of Maryland.
Title: Yoneda ontologies.
John Baez (Sep 16 2020 at 21:19):Date and Time: Wednesday November 18, 2020, 7:00 - 8:30 PM., on Zoom.
Speaker: Enrico Ghiorzi, Appalachian State University.
Title: Internal enriched categories.
John Baez (Sep 16 2020 at 21:19):Date and Time: Wednesday November 25, 2020, 7:00 - 8:30 PM., on Zoom.
Nothing yet.
John Baez (Sep 16 2020 at 21:20):Date and Time: Wednesday December 2, 2020, 7:00 - 8:30 PM., on Zoom.
Nothing yet.
John Baez (Sep 16 2020 at 21:20):Date and Time: Wednesday December 9, 2020, 7:00 - 8:30 PM., on Zoom.
Speaker: Dan Shiebler, Oxford University.
Title: Functorial Manifold Learning and Overlapping Clustering.
Matteo Capucci (he/him) (Sep 16 2020 at 23:11):Added to the calendar: https://teamup.com/ksfss6k4j1bxc8vztb
John Baez (Sep 17 2020 at 00:00):Thanks!!!
John Baez (Feb 09 2021 at 05:57):The New York City Category Theory Seminar is starting up again!
Wed Feb 10 19:00 Eastern Time: Peter Hines - Shuffling cards as an operad.
Wed Feb 17 19:00 Eastern Time: Richard Blute - Finiteness spaces, generalized polynomial rings and topological groupoids.
Wed Mar 03 19:00 Eastern Time: Joshua Sussan - Categorification and quantum topology.
Wed Mar 17 19:00 Eastern Time: Tobias Fritz - Categorical probability and the de Finetti theorem.
Wed Apr 14 19:00 Eastern Time: Ross Street - Absolute colimits for differential graded categories.
Wed May 05 19:00 Eastern Time: Juan Orendain - Categorical general boundary formulation.
John Baez (Feb 09 2021 at 05:59):The zoom information to log on will be posted on the Seminar Web page on the day of the talk, here:
http://www.sci.brooklyn.cuny.edu/~noson/CTseminar.html
You can also see abstracts for some talks there.
Some talks will be uploaded to YouTube here:
http://www.youtube.com/channel/UCNOfhimbNwZwJO2ltv1AZOw/videos
John Baez (Feb 09 2021 at 06:05):There are also a bunch of videos of talks already there!
John Baez (Feb 09 2021 at 06:29):Here's the talk this Wednesday, February 10th:
Speaker: Peter Hines, University of York.
Date and Time: Wednesday February 10, 2021, 19:00 - 20:30 Eastern Time, on Zoom.
Title: Shuffling cards as an operad.
Abstract: The theory of how two packs of cards may be shuffled together to form a single pack has been remarkably well-studied in combinatorics, group theory, statistics, and other areas of mathematics. This talk aims to study natural extensions where 1/ We may have infinitely many cards in a deck, 2/ We may take the result of a previous shuffle as one of our decks of cards (i.e. shuffles are hierarchical), and 3/ There may even be an infinite number of decks of cards.
Far from being 'generalisation for generalisation's sake', the original motivation came from theoretical & practical computer science. The mathematics of card shuffles is commonly used to describe processing in multi-threaded computations. Moving to the infinite case gives a language in which one may talk about potentially non-terminating processes, or servers with an unbounded number of clients, etc.
However, this talk is entirely about algebra & category theory -- just as in the finite case, the mathematics is of interest in its own right, and should be studied as such.
We model shuffles using operads. The intuition behind them of allowing for arbitrary n-ary operations that compose in a hierarchical manner makes them a natural, inevitable choice for describing such processes such as merging multiple packs of cards.
We use very concrete examples, based on endomorphism operads in groupoids of arithmetic operations. The resulting structures are at the same time both simple (i.e. elementary arithmetic operations), and related to deep structures in mathematics and category theory (topologies, tensors, coherence, associahedra, etc.)
We treat this as a feature, not a bug, and use it to describe complex structures in elementary terms. We also aim to give previously unobserved connections between distinct areas of mathematics.
Matteo Capucci (he/him) (Feb 09 2021 at 08:25):The NYC CT Seminar is great, but they don't have a machine-readable calendar anywhere. Do you think you're in a position to ask one to be created, @John Baez ? Otherwise I'll input the talk in the calendar by hand
Tom Hirschowitz (Feb 09 2021 at 08:59):@Matteo Capucci (he/him) Do you mean your personal calendar? Or is there a shared community calendar? That would be great, wouldn't it?
Matteo Capucci (he/him) (Feb 09 2021 at 09:06):Yes, there's a shared community calendar!
Tom Hirschowitz (Feb 09 2021 at 09:40):It is great!
Matteo Capucci (he/him) (Feb 09 2021 at 10:04)::)
Jules Hedges (Feb 09 2021 at 10:39):Neat, I ended up having to think a bunch about the operad of (order preserving) shuffles while thinking about the formal theory of comb diagrams... interleaving the legs of 2 combs is a lot like shuffling 2 packs of cards together... I have some unreleased notes where I defined that operad in purely categorical terms, I'll have to watch to compare notes :grinning_face_with_smiling_eyes:
John Baez (Feb 09 2021 at 16:52):@Matteo Capucci (he/him) asked:
The NYC CT Seminar is great, but they don't have a machine-readable calendar anywhere. Do you think you're in a position to ask one to be created?
Is their researchseminars.org calendar machine-readable?
https://researchseminars.org/seminar/Category_Theory
If not, that's a bit sad, because researchseminars.org is widely used.
Matteo Capucci (he/him) (Feb 09 2021 at 17:03):Definitely! I don't know how I missed that... I went for it immediately
Matteo Capucci (he/him) (Feb 09 2021 at 17:03):Indeed, most of the events on the community calendar come actually from my fav list on researchseminars.org
John Baez (Feb 09 2021 at 17:06):Ok, so I won't pester Noson Yanofsky, who runs that seminar.