Linked Questions

333 votes
34 answers
96k views

Why is a topology made up of 'open' sets? [closed]

I'm ashamed to admit it, but I don't think I've ever been able to genuinely motivate the definition of a topological space in an undergraduate course. Clearly, the definition distills the essence of ...
49 votes
28 answers
8k views

Problems where we can't make a canonical choice, solved by looking at all choices at once

It's a common theme in mathematics that, if there's no canonical choice (of basis, for example), then we shouldn't make a choice at all. This helps us focus on the heart of the matter without giving ...
53 votes
4 answers
24k views

When is $L^2(X)$ separable?

I have never studied any measure theory, so apologise in advance, if my question is easy: Let $X$ be a measure space. How can I decide whether $L^2(X)$ is separable? In reality, I am interested in ...
Bugs Bunny's user avatar
  • 12.3k
68 votes
2 answers
15k views

Is there a category structure one can place on measure spaces so that category-theoretic products exist?

The usual category of measure spaces consists of objects $(X, \mathcal{B}_X, \mu_X)$, where $X$ is a space, $\mathcal{B}_X$ is a $\sigma$-algebra on $X$, and $\mu_X$ is a measure on $X$, and measure ...
Damek Davis's user avatar
37 votes
5 answers
4k views

Reference for the Gelfand duality theorem for commutative von Neumann algebras

The Gelfand duality theorem for commutative von Neumann algebras states that the following three categories are equivalent: (1) The opposite category of the category of commutative von Neumann ...
Dmitri Pavlov's user avatar
27 votes
3 answers
4k views

Why is free probability a generalization of probability theory?

Note: This question was already asked on Math.SE nearly a week and a half ago but did not receive any responses. To the best of my knowledge, free probability is an active topic of research, so I hope ...
Chill2Macht's user avatar
  • 2,680
17 votes
4 answers
2k views

Good introduction to statistics from a algebraic point of view?

There are already lots of questions on this subject like Is there an introduction to probability theory from a structuralist/categorical perspective? Is there a combinatorial/topological treatment ...
doofin's user avatar
  • 283
26 votes
2 answers
3k views

Corollaries of the Yoneda Lemma in Analysis?

This is a cross-post of my ~2 weeks (canonically) unanswered question on Math.SE: https://math.stackexchange.com/questions/1830287/corollaries-of-the-yoneda-lemma-in-analysis. I am looking for some ...
Chill2Macht's user avatar
  • 2,680
25 votes
1 answer
1k views

Is the opposite category of commutative von Neumann algebras a topos?

By the "category of commutative von Neumann algebras" I mean the category of all commutative von Neumann algebras with normal unital $*$-homomorphisms between them (I don't want to restrict ...
Simon Henry's user avatar
  • 42.4k
15 votes
2 answers
1k views

Analytical origins of the Stone duality

I've asked this question in the HSM community, but by the nature of my question, some user told me to ask this question here. This is the original post https://hsm.stackexchange.com/q/13087/14296 ...
IJM98's user avatar
  • 281
11 votes
2 answers
1k views

Is there a relation between Gelfand duality and the spectrum of a ring (with its Zariski topology)?

Compare the following two results: Thm A) Let $A$ be a commutative $C^*$-algebra and let $X$ be its Gelfand spectrum. Gelfand duality says that there's a natural isometric $*$-isomorphism from $A$ to ...
Gabriel's user avatar
  • 711
3 votes
3 answers
654 views

Free probability with unbounded random variables?

This is partially inspired by this question and this blog post. When trying to express classical probability in the "free probability" setting one takes an algebra of random variables equipped with ...
Stefan Perko's user avatar
10 votes
2 answers
2k views

random category theory

This question is in some sense dual to the one asked in Is there an introduction to probability theory from a structuralist/categorical perspective? since contrary to the OP who asks for references ...
Sylvain JULIEN's user avatar
10 votes
2 answers
1k views

Why Kleisli Markov categories and not the Eilenberg-Moore categories of the associated monads

Why is there so much interest in the Markov categories which are Kleisli categories for monads corresponding to distributions etc. but not much discussion of the E.M. categories? For example, the E.M. ...
Q.Faustus's user avatar
  • 101
12 votes
1 answer
2k views

Making sense of "every non-commutative algebra has its own internal time evolution (aka a one-parameter group)"?

I've listened to many interviews and lectures of Alain Connes, in which he says something which goes roughly as follows "Every non-commutative algebra has its own time (evolution of), by which I ...
dohmatob's user avatar
  • 6,853

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