User Tony Huynh

65 votes

What are your favorite instructional counterexamples?

answered Mar 3, 2010 at 18:12

51 votes

Major mathematical advances past age fifty

answered May 23, 2010 at 7:20

44 votes

Accepted

For consecutive primes $a\lt b\lt c$, prove that $a+b\ge c$.

answered Nov 19, 2012 at 16:27

41 votes

Accepted

What happens if you strip everything but the “between” relation in metric spaces

answered Mar 31, 2020 at 13:47

40 votes

What are the external triumphs of matroid theory?

answered May 3, 2011 at 21:51

37 votes

When are two proofs of the same theorem really different proofs

answered Sep 27, 2014 at 17:49

36 votes

Accepted

Can one measure the infeasibility of four color proofs?

answered Sep 16, 2013 at 0:34

32 votes

Accepted

Function of $(x_1,x_2,x_3,x_4)$ that factors in two ways as $\phi_1 (x_1 ,x_2 )\phi_2(x_3 ,x_4 )=\psi_1 (x_1,x_3)\psi_2(x_2,x_4)$

answered Oct 16, 2020 at 6:54

31 votes

Obstructions for embedding a graph on a surface of genus g

answered Nov 19, 2010 at 18:37

29 votes

What are your favorite instructional counterexamples?

answered Mar 3, 2010 at 16:50

29 votes

Important open problems that have already been reduced to a finite but infeasible amount of computation

answered Nov 11, 2012 at 23:42

28 votes

Can a problem be simultaneously polynomial time and undecidable?

answered Dec 2, 2010 at 10:14

28 votes

Most intricate and most beautiful structures in mathematics

answered Dec 17, 2010 at 17:18

25 votes

What is your favorite isomorphism?

answered Sep 2, 2010 at 19:29

25 votes

Can a convex polytope with $f$ facets have more than $f$ facets when projected into $\mathbb{R}^2$?

answered Jan 21, 2017 at 18:02

23 votes

Difficult examples for Frankl's union-closed conjecture

answered Nov 6, 2016 at 17:34

23 votes

What well known results with countability assumptions can be naturally extended to uncountable settings?

answered Jan 7, 2022 at 2:17

23 votes

Accepted

Realizing groups as automorphism groups of graphs.

answered Sep 1, 2010 at 8:30

23 votes

How to tell if two random polynomials are identical

answered Sep 23, 2010 at 14:00

23 votes

Counting non-isomorphic graphs with prescribed number of edges and vertices

answered Jun 17, 2011 at 3:22

22 votes

Generalizing a problem to make it easier

answered Sep 26, 2010 at 12:48

22 votes

Does minimal degree $n$ imply a $K_n$ minor

answered Jan 31, 2020 at 16:36

20 votes

Menger's theorem via matroids

answered Nov 17, 2010 at 15:44

19 votes

Is there a version of König's theorem for tripartite 3-graphs?

answered Apr 29, 2010 at 2:41

19 votes

Does every convex polyhedron have a combinatorially isomorphic counterpart whose faces all have rational areas?

answered May 4, 2013 at 23:08

19 votes

Accepted

Lagrange four-squares theorem --- deterministic complexity

answered Apr 19, 2019 at 14:36

18 votes

Accepted

Category theoretic interpretation of matroids?

answered Mar 16, 2010 at 1:03

18 votes

Favorite popular math book

answered Feb 24, 2010 at 21:46

17 votes

Applications of infinite graph theory

answered Sep 22, 2010 at 22:26

17 votes

The concept of duality

answered Sep 11, 2011 at 7:26

Stack Exchange Network

475 Answers

What are your favorite instructional counterexamples?

Major mathematical advances past age fifty

For consecutive primes $a\lt b\lt c$, prove that $a+b\ge c$.

What happens if you strip everything but the “between” relation in metric spaces

What are the external triumphs of matroid theory?

When are two proofs of the same theorem really different proofs

Can one measure the infeasibility of four color proofs?

Function of $(x_1,x_2,x_3,x_4)$ that factors in two ways as $\phi_1 (x_1 ,x_2 )\phi_2(x_3 ,x_4 )=\psi_1 (x_1,x_3)\psi_2(x_2,x_4)$

Obstructions for embedding a graph on a surface of genus g

What are your favorite instructional counterexamples?

Important open problems that have already been reduced to a finite but infeasible amount of computation

Can a problem be simultaneously polynomial time and undecidable?

Most intricate and most beautiful structures in mathematics

What is your favorite isomorphism?

Can a convex polytope with $f$ facets have more than $f$ facets when projected into $\mathbb{R}^2$?

Difficult examples for Frankl's union-closed conjecture

What well known results with countability assumptions can be naturally extended to uncountable settings?

Realizing groups as automorphism groups of graphs.

How to tell if two random polynomials are identical

Counting non-isomorphic graphs with prescribed number of edges and vertices

Generalizing a problem to make it easier

Does minimal degree $n$ imply a $K_n$ minor

Menger's theorem via matroids

Is there a version of König's theorem for tripartite 3-graphs?

Does every convex polyhedron have a combinatorially isomorphic counterpart whose faces all have rational areas?

Lagrange four-squares theorem --- deterministic complexity

Category theoretic interpretation of matroids?

Favorite popular math book

Applications of infinite graph theory

The concept of duality