darij grinberg's user avatar
darij grinberg's user avatar
darij grinberg's user avatar
darij grinberg
  • Member for 14 years, 3 months
  • Last seen this week
57 votes
5 answers
8k views

How to make Ext and Tor constructive?

82 votes
4 answers
7k views

Wanted: a "Coq for the working mathematician"

44 votes
4 answers
7k views

What motivates modern algebraic geometry for a combinatorial/constructive algebraist?

52 votes
3 answers
7k views

Function extensionality: does it make a difference? why would one keep it out of the axioms?

12 votes
1 answer
6k views

Chinese Remainder Theorem for rings: why not for modules?

45 votes
3 answers
5k views

Putnam 2020 inequality for complex numbers in the unit circle

48 votes
4 answers
5k views

How to constructively/combinatorially prove Schur-Weyl duality?

12 votes
5 answers
5k views

reduced ⊗ reduced = reduced; what about connected?

30 votes
7 answers
5k views

Shuffle Hopf algebra: how to prove its properties in a slick way?

64 votes
1 answer
4k views

How to be rigorous about combinatorial algorithms?

17 votes
4 answers
4k views

Induction of tensor product vs. tensor product of inductions

9 votes
2 answers
3k views

Jacobson radical = intersection of all maximal two-sided ideals

39 votes
4 answers
3k views

Chain homotopy: Why du+ud and not du+vd?

22 votes
3 answers
3k views

Splitting the determinant polynomial into linear factors - a Dedekind problem

29 votes
4 answers
3k views

A mysterious Heisenberg algebra identity from Sylvester, 1867

11 votes
3 answers
3k views

Gauss sum (with sign) through algebra

26 votes
6 answers
2k views

Why is the right permutohedron order (aka weak order) on $S_n$ a lattice?

8 votes
4 answers
2k views

"Why" is every polynomial representation of SL(2) selfdual?

10 votes
1 answer
2k views

Sum of difference moduli vs. sum of modulus differences

32 votes
2 answers
2k views

Generalization of Tamarkin's ARO 1993, final round, problem 10/8: still a conjecture?

4 votes
1 answer
2k views

Create djvu from jpeg - best practices and tutorial? [closed]

13 votes
2 answers
2k views

How ugly is the isomorphism R[GxH] = R[G] (X) R[H] for groups G, H?

31 votes
2 answers
2k views

The logic of convex sets

21 votes
2 answers
2k views

Has Reifegerste's Theorem on RSK and Knuth relations received a slick proof by now?

18 votes
3 answers
2k views

A binomial sum is divisible by p^2

15 votes
3 answers
2k views

Hom(A,C) ⊗ Hom(B,D) injects into Hom(A⊗B,C⊗D): when? why?

8 votes
1 answer
2k views

Condition on a bipartite graph to have an $m$-factor

13 votes
4 answers
2k views

Representations of Pin vs. Representations of Clifford

15 votes
1 answer
2k views

Graded commutativity of cup in Hochschild cohomology

31 votes
3 answers
2k views

"Nyldon words": understanding a class of words factorizing the free monoid increasingly

1
2 3 4 5 6