User Qiaochu Yuan

33 votes

Mathematicians who were late learners?-list

answered Oct 31, 2009 at 20:38

99 votes

Your favorite surprising connections in mathematics

answered Feb 8, 2010 at 5:13

12 votes

How is it possible for PA+¬Con(PA) to be consistent?

answered Oct 5, 2023 at 5:22

5 votes

Epimorphisms of relations

answered Sep 26, 2023 at 3:26

7 votes

Understanding the condition $\frac{1}{p} + \frac{1}{q} = 1$ in the estimate $xy \le \frac{1}{p}x^p + \frac{1}{q}y^q$

answered Sep 25, 2023 at 7:21

4 votes

Accepted

Is a compactly generated Hausdorff space functionally Hausdorff?

answered Sep 23, 2010 at 0:45

20 votes

Are there any undecidability results that are not known to have a diagonal argument proof?

answered Sep 7, 2023 at 2:23

12 votes

Reference for group-algebra/exp-log like identites in combinatorics

answered Sep 1, 2023 at 19:27

2 votes

Knot theory without planar diagrams?

answered Aug 6, 2012 at 18:19

4 votes

Why are characters so well-behaved?

answered Oct 27, 2009 at 14:28

10 votes

Formal power series vs localization at non-constant polynomials

answered Feb 13, 2023 at 22:19

10 votes

Accepted

Why is $\operatorname{SO}(4)$ not a simple Lie group?

answered Feb 10, 2023 at 19:46

9 votes

Which functors preserve the number of connected components?

answered Oct 29, 2022 at 18:22

13 votes

Computation on characteristic classes

answered Jan 30, 2023 at 21:53

5 votes

Proofs of the Frobenius characteristic map

answered Jan 27, 2023 at 7:16

5 votes

Accepted

Classification of Lie group structures on $\mathbb{R}^n$

answered Jan 24, 2023 at 8:25

10 votes

Counting degrees of freedom in Lie algebra structure constants (aka why are there any nontrivial Lie algebras of dim >5?)

answered Jan 18, 2023 at 23:06

2 votes

Classifications of finite simple objects

answered Apr 3, 2011 at 18:00

10 votes

Accepted

Reference for a proof of Euclid's Theorem for the infinitude of primes

answered Dec 28, 2022 at 16:38

13 votes

Does anyone still seriously doubt the consistency of $ZFC$?

answered Dec 25, 2022 at 2:39

10 votes

Combinatorial results without known combinatorial proofs

answered Nov 13, 2009 at 22:44

13 votes

Axioms for the category of groups

answered Oct 22, 2022 at 1:50

10 votes

Is Monsky's theorem provable in $\mathsf{RCA}_0$?

answered Oct 12, 2022 at 2:32

36 votes

Do rings of smooth functions differ from rings of continuous functions?

answered Oct 3, 2022 at 2:04

2 votes

"C choose k" where C is topological space

answered Dec 29, 2010 at 15:57

8 votes

Arrows, furnished by Yoneda

answered Sep 28, 2022 at 22:11

21 votes

Is $e^{{e^{\ \dots\ }}^n}$ ever an integer?

answered Sep 28, 2022 at 5:39

5 votes

Wild classification problems and Borel reducibility

answered Sep 23, 2022 at 22:43

2 votes

Does the Lie algebra structure on rational homotopy groups reflect similar information to the formal group structure in characteristic p?

answered Sep 23, 2022 at 20:25

4 votes

Accepted

In what sense is Bass-Serre theory the one-dimensional version of orbifold theory

answered Sep 23, 2022 at 21:11

Stack Exchange Network

931 Answers

Mathematicians who were late learners?-list

Your favorite surprising connections in mathematics

How is it possible for PA+¬Con(PA) to be consistent?

Epimorphisms of relations

Understanding the condition $\frac{1}{p} + \frac{1}{q} = 1$ in the estimate $xy \le \frac{1}{p}x^p + \frac{1}{q}y^q$

Is a compactly generated Hausdorff space functionally Hausdorff?

Are there any undecidability results that are not known to have a diagonal argument proof?

Reference for group-algebra/exp-log like identites in combinatorics

Knot theory without planar diagrams?

Why are characters so well-behaved?

Formal power series vs localization at non-constant polynomials

Why is $\operatorname{SO}(4)$ not a simple Lie group?

Which functors preserve the number of connected components?

Computation on characteristic classes

Proofs of the Frobenius characteristic map

Classification of Lie group structures on $\mathbb{R}^n$

Counting degrees of freedom in Lie algebra structure constants (aka why are there any nontrivial Lie algebras of dim >5?)

Classifications of finite simple objects

Reference for a proof of Euclid's Theorem for the infinitude of primes

Does anyone still seriously doubt the consistency of $ZFC$?

Combinatorial results without known combinatorial proofs

Axioms for the category of groups

Is Monsky's theorem provable in $\mathsf{RCA}_0$?

Do rings of smooth functions differ from rings of continuous functions?

"C choose k" where C is topological space

Arrows, furnished by Yoneda

Is $e^{{e^{\ \dots\ }}^n}$ ever an integer?

Wild classification problems and Borel reducibility

Does the Lie algebra structure on rational homotopy groups reflect similar information to the formal group structure in characteristic p?

In what sense is Bass-Serre theory the one-dimensional version of orbifold theory