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

18 votes
3 answers
1k views

Is there a natural measurable structure on the $\sigma$-algebra of a measurable space?

Let $(X, \Sigma)$ denote a measurable space. Is there a non-trivial $\sigma$-algebra $\Sigma^1$ of subsets of $\Sigma$ so that $(\Sigma, \Sigma^1)$ is also a measurable space? Here is one natural …
6 votes

Corollaries of the Yoneda Lemma in Analysis?

Thanks William for reaching out (and thanks David Roberts for the hat tip to my talk). Let me give an intentionally fuzzy, high-level answer. Generally speaking, the Yoneda Lemma allows you to make a …
David Roberts's user avatar
  • 35.5k
4 votes
0 answers
128 views

Metrized categories

Motivation: Let $\Gamma = (V,E)$ be a directed graph. To each edge $e \in E$, choose a value $\kappa^e \in \mathbb R$, representing the cost of transporting one unit of "stuff" through the edge. Let $ …
3 votes
3 answers
425 views

What are the symmetries of a principal homogeneous bundle?

Let $\operatorname{Klein}$ denote the category of principal homogeneous bundles. An object in this category is a tuple $\mathbf Q = (Q, P; G, H; q, a, \tilde a)$, where: $G$ is a Lie group, and $H$ …
39 votes
4 answers
5k views

What is an $(\infty,1)$-topos, and why is this a good setting for doing differential geometry?

In this post on the n-Category Café, Urs Schreiber says that, "The theory of G-principal bundles makes sense in any $(\infty,1)$-topos." I followed the link to the nLab and tried to chase definitions, …
7 votes

Can one view the Independent Product in Probability categorially?

One resource you may like is this recent paper by Culbertson and Sturtz on A Categorical Foundation for Bayesian Probability. Here are some thoughts on the category $\mathrm{Meas}$ of measurable sp …
Tom LaGatta's user avatar
  • 8,532
18 votes
1 answer
1k views

Applications of the Giry monad in probability and statistics

In another thread, I asked about the $M$ endofunctor on the category $\operatorname{Meas}$ of measurable spaces, which sends a space $X$ to its space of measures $M(X)$. Will Sawin described the mon …
2 votes

Fixed objects of the M endofunctor on category Meas

Here is a candidate class of examples. I have made this community wiki so please feel free to edit it if you can answer it. Or, copy the text and make a new answer so we can give you reputation points …
Tom LaGatta's user avatar
  • 8,532
9 votes
2 answers
586 views

Fixed objects of the M endofunctor on category Meas

Consider the category $\operatorname{Meas}$ of measurable spaces: its objects are sets equipped with $\sigma$-algebras, and its morphisms are measurable functions between spaces. As Gerald Edgar & M …
5 votes
0 answers
198 views

Diffusion processes in wide generality

It is common knowledge among schoolchildren that one may define jump diffusion processes in wide generality. Hard question: What are the most general structures on which one may define something whi …