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Enriched categories, topoi, abelian categories, monoidal categories, homological algebra.

36 votes
3 answers
3k views

The set-theoretic multiverse as a (bi)category

Joel Hamkin's The set-theoretic multiverse has featured in MO questions before, e.g., here and here. But I was wondering about the best category theoretic angle to take on it. In the paper Joel write …
David Corfield's user avatar
25 votes

whence commutative diagrams?

There's Russell's example from 1919, see here where conjugacy between relations is expressed diagrammatically.
David Corfield's user avatar
21 votes
2 answers
1k views

When and why do universal objects have extra properties?

I'm interested in situations where universal objects come with more structure than their definitions suggest. A classic case of this is where the free abelian group on one element has a ring structure …
David Corfield's user avatar
13 votes
0 answers
337 views

Is there a common framework for Tannaka and Gabriel-Ulmer reconstruction theorems?

Gabriel-Ulmer duality is a biequivalence between the 2-category of finite limit categories and the 2-category of locally finitely presentable categories. It allows for the reconstruction of a theory f …
David Corfield's user avatar
11 votes

Is there an introduction to probability theory from a structuralist/categorical perspective?

For a recent approach that looks to provide a better categorical environment for probability theory: Chris Heunen, Ohad Kammar, Sam Staton, Hongseok Yang, A Convenient Category for Higher-Order Prob …
David Corfield's user avatar
10 votes
Accepted

Reference request: 2-Grothendieck Construction

I. Bakovic, Grothendieck construction for bicategories.
David Corfield's user avatar
9 votes

What is an Elementary "Homotopy, Model" Topos?

Since the time when Denis referred in the comments to the relevant nLab page, there has been a new proposal written up by Mike Shulman there: An elementary $(\infty,1)$-topos is an $(\infty,1)$-categ …
David Corfield's user avatar
9 votes

What are some examples of interesting uses of the theory of combinatorial species?

One further line of response would again invoke Rota: "What can you prove with exterior algebra that you cannot prove without it?" Whenever you hear this question raised about some new piece …
David Corfield's user avatar
8 votes
0 answers
445 views

Does any 'logical' theory have a bounded ∞-pretopos as syntactic category?

Stone duality may be understood as providing a duality between syntax and semantics for propositional logic, so that a theory may be recovered from its models. In order to do likewise for first-order …
David Corfield's user avatar
7 votes

What can't be described by categories?

There's an interesting variant of your question, which may perhaps have been included in the first part of it, as to whether there are parts of mathematics where categories have little traction, and w …
David Corfield's user avatar
6 votes
Accepted

A terminal coalgebra of a certain functor on Mes

Final coalgebras for functors on measurable spaces, Lawrence S. Moss and Ignacio D. Viglizzo: "We prove that every functor on the category Meas of measurable spaces built from the identity and consta …
David Corfield's user avatar
6 votes

Categorification of logic

Try Mike Shulman's page.
David Corfield's user avatar
6 votes

What is a monoidal metric space?

Did you follow the thread Simon Willerton started on profunctors between metric spaces, which took us all the way to optimal transport theory?
David Corfield's user avatar
6 votes

What is the precise relationship between pyknoticity and cohesiveness?

We have a case of relative cohesion used in an algebraic geometric setting discussed at the nLab. The entry for differential algebraic K-theory interprets Ulrich Bunke, Georg Tamme, Regulators and …
David Corfield's user avatar
5 votes

Is there a relationship between model theory and category theory?

We had a chat about this topic over here, prompted by remarks by David Kazhdan.
David Corfield's user avatar

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