Wilberd van der Kallen's user avatar
Wilberd van der Kallen's user avatar
Wilberd van der Kallen's user avatar
Wilberd van der Kallen
  • Member for 14 years
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51 votes

Conceptual reason why the sign of a permutation is well-defined?

35 votes
Accepted

How to prove this polynomial always has integer values at all integers?

21 votes
Accepted

Universal cover of SL2(R) admits no central extensions?

14 votes
Accepted

Is Lusztig's conjecture solved?

14 votes
Accepted

Tensor product of rings of Witt vectors

14 votes
Accepted

Invariants of matrices (by simultaneous $\mathrm{GL}_n$ conjugation) over arbitrary rings

11 votes

Non-finite version of Nakayama's lemma?

10 votes
Accepted

Question about the representation theory of SL(n,Z)

9 votes

Proper subgroup of GL(n,Z) isomorphic to GL(n,Z)?

9 votes

Normalizer of SL_2(Z) in GL_2(R)

8 votes
Accepted

Are homogeneous components of f.g graded modules f.g ?

8 votes

How to think about parabolic induction.

8 votes
Accepted

For regular tetrahedron $ABCD$ with center $O$, and $\overrightarrow{NO}=-3\overrightarrow{MO}$, is $NA+NB+NC+ND\geq MA+MB+MC+MD$?

8 votes
Accepted

Connected components of the orthogonal group O(2n) in characteristic 2.

7 votes
Accepted

Subgroups of $GL_n(\mathbb Z)$ with finite coinvariants

7 votes

Isomorphism between varieties of char 0

7 votes

GIT over integers

6 votes
Accepted

Lifting $G$-invariants from characteristic $p\gg 0$ to characteristic 0 for a reductive algebraic group $G$

6 votes
Accepted

Global homological dimension of reductive groups

6 votes

Polynomial ring $S[X]$ over domain $S$

5 votes
Accepted

Behavior of invariants under reduction mod p

5 votes

A question about the additive group of a finitely generated integral domain

5 votes
Accepted

Can the 'linkages' between equivalent extensions of modules of an algebraic group be taken to have bounded length?

5 votes
Accepted

Intersections of conjugates of the icosahedral group in SO(3)

5 votes

Applications of finite continued fractions

4 votes

Are the Weyl modules projectives?

4 votes

$R$ a DVR with fraction field $K.$ What are the $R$-submodules of $K^n?$

4 votes
Accepted

Tilting modules in positive characteristic

3 votes
Accepted

finite generation of a certain type of subring

3 votes

Quotient space of algebraic group