User Sam Hopkins

99 votes

3 answers

5k views

Why do combinatorial abstractions of geometric objects behave so well?

asked Nov 27, 2016 at 18:55

39 votes

17 answers

8k views

Examples of "unsuccessful" theories with afterlives

asked Sep 18, 2019 at 22:06

34 votes

1 answer

3k views

Updates to Stanley's 1999 survey of positivity problems in algebraic combinatorics?

asked Dec 30, 2019 at 22:17

23 votes

1 answer

970 views

Why 'excedances' of permutations? [closed]

asked May 8, 2020 at 1:24

22 votes

3 answers

1k views

Cyclic action on Kreweras walks

asked Feb 1, 2020 at 20:12

21 votes

4 answers

3k views

Which fields have multiplicative group isomorphic to additive group times Z/2Z?

asked Nov 15, 2013 at 6:09

20 votes

2 answers

854 views

Counting problems where unlabeled is easier than labeled

asked Mar 6, 2016 at 22:04

20 votes

4 answers

2k views

Non-enumerative proof that, in average, less than 50% of tiles in domino tiling of 2-by-n rectangle are vertical?

asked Sep 9, 2021 at 1:28

19 votes

1 answer

2k views

Why did _Research in the Mathematical Sciences_ change from open access to subscription-based?

asked Aug 23, 2018 at 21:38

19 votes

2 answers

1k views

Is it possible that the GHKK canonical basis for cluster algebras is the Lusztig/Kashiwara dual canonical basis?

asked Jul 5, 2019 at 9:11

17 votes

0 answers

796 views

Is there a n/2 version of the Erdős-Hanani conjecture?

asked Feb 16, 2013 at 1:02

17 votes

3 answers

711 views

Matrices of combinatorial sequences that are inverse in two ways

asked Mar 16, 2022 at 12:53

16 votes

0 answers

322 views

Row of the character table of symmetric group with most negative entries

asked Apr 22, 2022 at 16:54

15 votes

5 answers

1k views

Longest increasing subsequence as measure of randomness

asked Apr 13, 2022 at 16:31

15 votes

2 answers

518 views

Is there a natural notion of completion of a Coxeter system?

asked Mar 5, 2014 at 3:24

15 votes

4 answers

674 views

Unified framework for posets with order polynomial product formulas

asked Jul 31, 2019 at 2:02

14 votes

2 answers

432 views

Ehrhart period collapse for $123\ldots k$-avoiding Birkhoff polytope?

asked Jan 1, 2021 at 3:07

14 votes

3 answers

657 views

Log-concavity of matroids: characterization of equality?

asked May 1, 2021 at 20:15

13 votes

2 answers

787 views

Cycle generating function of permutations with only odd cycles

asked Aug 13, 2018 at 15:32

13 votes

1 answer

514 views

Minuscule weights of parabolic sub-root systems are not far from dominant

asked Mar 2, 2018 at 23:06

13 votes

2 answers

694 views

Basis of coinvariant algebra on which reflection group acts as regular representation

asked Apr 30, 2018 at 17:40

13 votes

2 answers

976 views

Significance of half-sum of positive roots belonging to root lattice?

asked Nov 30, 2016 at 17:58

13 votes

1 answer

518 views

Bijective proof of recurrence for rooted unlabeled trees

asked Nov 25, 2021 at 23:59

12 votes

3 answers

885 views

Expected number of compositions needed to get constant function

asked Dec 1, 2021 at 12:19

12 votes

2 answers

485 views

Dynamics of RSK

asked Feb 6, 2015 at 15:08

12 votes

1 answer

589 views

Order polynomial of shifted double staircase

asked Oct 3, 2019 at 1:02

11 votes

6 answers

4k views

Non-constructive proofs vs. efficient algorithms

asked Dec 30, 2012 at 0:25

11 votes

1 answer

242 views

Infinite vertex-transitive graph where every automorphism has a fixed vertex

asked Apr 19, 2022 at 18:43

10 votes

1 answer

177 views

Reversals of autonomous subsets in right-angled Coxeter groups

asked Nov 17, 2021 at 15:45

10 votes

0 answers

341 views

Pattern Avoidance in Poset Permutations

asked Jul 31, 2015 at 1:40

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105 Questions

Why do combinatorial abstractions of geometric objects behave so well?

Examples of "unsuccessful" theories with afterlives

Updates to Stanley's 1999 survey of positivity problems in algebraic combinatorics?

Why 'excedances' of permutations? [closed]

Cyclic action on Kreweras walks

Which fields have multiplicative group isomorphic to additive group times Z/2Z?

Counting problems where unlabeled is easier than labeled

Non-enumerative proof that, in average, less than 50% of tiles in domino tiling of 2-by-n rectangle are vertical?

Why did _Research in the Mathematical Sciences_ change from open access to subscription-based?

Is it possible that the GHKK canonical basis for cluster algebras is the Lusztig/Kashiwara dual canonical basis?

Is there a n/2 version of the Erdős-Hanani conjecture?

Matrices of combinatorial sequences that are inverse in two ways

Row of the character table of symmetric group with most negative entries

Longest increasing subsequence as measure of randomness

Is there a natural notion of completion of a Coxeter system?

Unified framework for posets with order polynomial product formulas

Ehrhart period collapse for $123\ldots k$-avoiding Birkhoff polytope?

Log-concavity of matroids: characterization of equality?

Cycle generating function of permutations with only odd cycles

Minuscule weights of parabolic sub-root systems are not far from dominant

Basis of coinvariant algebra on which reflection group acts as regular representation

Significance of half-sum of positive roots belonging to root lattice?

Bijective proof of recurrence for rooted unlabeled trees

Expected number of compositions needed to get constant function

Dynamics of RSK

Order polynomial of shifted double staircase

Non-constructive proofs vs. efficient algorithms

Infinite vertex-transitive graph where every automorphism has a fixed vertex

Reversals of autonomous subsets in right-angled Coxeter groups

Pattern Avoidance in Poset Permutations