English

Commuting varieties in bad characteristic

Algebraic Geometry 2026-02-04 v1 Rings and Algebras Representation Theory

Abstract

Let kk be an algebraically closed field of characteristic 22. We consider the commuting variety and the commuting nilpotent variety of the Lie algebra sp2n\mathfrak{sp}_{2n}, namely the sets C2(sp2n)={(x,y)sp2n×sp2n[x,y]=0}\mathcal{C}_2(\mathfrak{sp}_{2n})=\{ (x,y) \in \mathfrak{sp}_{2n} \times \mathfrak{sp}_{2n} \mid [x,y]=0\} and C2nil(sp2n)={(x,y)sp2n×sp2nx,y nilpotent, [x,y]=0}\mathcal{C}_2^{\text{nil}}(\mathfrak{sp}_{2n})=\{ (x,y) \in \mathfrak{sp}_{2n} \times \mathfrak{sp}_{2n} \mid x,y \text{ nilpotent, } [x,y]=0\} and prove that they are both irreducible, of dimensions dim(sp2n)+2n\dim(\mathfrak{sp}_{2n}) + 2n and dim(sp2n)+n1\dim(\mathfrak{sp}_{2n}) + n-1, respectively.

Keywords

Cite

@article{arxiv.2602.02935,
  title  = {Commuting varieties in bad characteristic},
  author = {Vlad Roman},
  journal= {arXiv preprint arXiv:2602.02935},
  year   = {2026}
}
R2 v1 2026-07-01T09:33:13.465Z