User Anton Fetisov

62 votes

Intuition for coends

answered Nov 11, 2011 at 23:16

47 votes

No matter how many algebraic invariants we attach to topological spaces, there will always be nonhomeomorphic spaces agreeing on all their invariants

answered Mar 23, 2016 at 11:33

24 votes

Nonequivalent definitions in Mathematics

answered Nov 23, 2017 at 2:04

19 votes

Accepted

Semi group of polynomials which all roots lie on the unit circle

answered Nov 28, 2017 at 22:54

12 votes

What's a good introduction to category theory for someone doing analysis?

answered Aug 16, 2015 at 23:22

12 votes

Accepted

Delooping in homotopy type theory

answered Aug 10, 2014 at 21:36

11 votes

Accepted

Topology of categories, very basic facts surrounding Quillen's Higher Algebraic K-Theory I

answered Dec 5, 2015 at 17:55

11 votes

Accepted

Connective spectra and infinite loop spaces

answered Sep 12, 2017 at 20:22

10 votes

An abstract nonsense proof of the Hurewicz theorem

answered Oct 11, 2017 at 19:43

10 votes

Accepted

Automorphisms of Eilenberg-Mac Lane spaces and semidirect products (and the odd line)

answered Nov 8, 2015 at 11:30

10 votes

Accepted

What is the significance of the Spec of non-affine structure sheaf sections?

answered Dec 4, 2013 at 2:21

8 votes

Accepted

Is lim R_i = O(colim Spec R_i) true for finite (co)limits?

answered Apr 2, 2012 at 20:33

8 votes

What is Yoneda's Lemma a generalization of?

answered Jan 22, 2012 at 0:28

8 votes

Is there an algebraic approach to metric spaces?

answered Apr 1, 2012 at 15:01

8 votes

Accepted

What is the relationship between $BU$ and $\textrm{Fred}_0(H)$?

answered Nov 11, 2014 at 2:47

8 votes

Can one make a category concrete by "enlarging the universe"?

answered Dec 13, 2014 at 0:52

8 votes

Accepted

"Monoid objects" without points

answered Dec 22, 2017 at 17:43

7 votes

The main theorems of category theory and their applications

answered Dec 15, 2011 at 0:42

7 votes

What is the homotopy fiber of a fold map?

answered Jun 26, 2013 at 19:27

6 votes

What is the canonical isomorphism between the tensor products of the top exterior powers associated to exact sequences of vector spaces?

answered Apr 29, 2012 at 1:22

6 votes

Accepted

Can Homotopy Type Theory or algebraic geometry deal with homotopy fibers in terms of families?

answered Dec 8, 2017 at 3:14

5 votes

Accepted

Is there an analog of adjoint functor theorem for adjunctions of two variables?

answered Mar 21, 2013 at 13:19

5 votes

Examples of toposes for analysts

answered Dec 19, 2013 at 21:04

5 votes

Accepted

Isomorphism class of locally trivial object classified by some $H^1$ ?

answered Mar 15, 2012 at 9:15

4 votes

Interesting Calculus Questions/Exercises

answered Apr 1, 2012 at 15:21

4 votes

The groupoid of algebraic expressions and proofs

answered Feb 19, 2015 at 22:53

4 votes

Accepted

How to proceed with a type-theoretic proof that $\Sigma \mathbb{S}^1 \simeq \mathbb{S}^2$?

answered Feb 19, 2015 at 23:42

4 votes

If a $\otimes$-idempotent object has a dual, must it be self-dual?

answered Aug 9, 2017 at 0:28

4 votes

Accepted

A groupoid which is homotopy equivalent to $BG$

answered Dec 7, 2017 at 11:27

3 votes

Special $\Gamma$-categories and symmetric monoidal categories

answered Nov 12, 2017 at 22:17

Stack Exchange Network

42 Answers

Intuition for coends

No matter how many algebraic invariants we attach to topological spaces, there will always be nonhomeomorphic spaces agreeing on all their invariants

Nonequivalent definitions in Mathematics

Semi group of polynomials which all roots lie on the unit circle

What's a good introduction to category theory for someone doing analysis?

Delooping in homotopy type theory

Topology of categories, very basic facts surrounding Quillen's Higher Algebraic K-Theory I

Connective spectra and infinite loop spaces

An abstract nonsense proof of the Hurewicz theorem

Automorphisms of Eilenberg-Mac Lane spaces and semidirect products (and the odd line)

What is the significance of the Spec of non-affine structure sheaf sections?

Is lim R_i = O(colim Spec R_i) true for finite (co)limits?

What is Yoneda's Lemma a generalization of?

Is there an algebraic approach to metric spaces?

What is the relationship between $BU$ and $\textrm{Fred}_0(H)$?

Can one make a category concrete by "enlarging the universe"?

"Monoid objects" without points

The main theorems of category theory and their applications

What is the homotopy fiber of a fold map?

What is the canonical isomorphism between the tensor products of the top exterior powers associated to exact sequences of vector spaces?

Can Homotopy Type Theory or algebraic geometry deal with homotopy fibers in terms of families?

Is there an analog of adjoint functor theorem for adjunctions of two variables?

Examples of toposes for analysts

Isomorphism class of locally trivial object classified by some $H^1$ ?

Interesting Calculus Questions/Exercises

The groupoid of algebraic expressions and proofs

How to proceed with a type-theoretic proof that $\Sigma \mathbb{S}^1 \simeq \mathbb{S}^2$?

If a $\otimes$-idempotent object has a dual, must it be self-dual?

A groupoid which is homotopy equivalent to $BG$

Special $\Gamma$-categories and symmetric monoidal categories