English

Holomorphic differentials of alternating four covers

Algebraic Geometry 2025-10-20 v1 Number Theory

Abstract

Suppose kk is an algebraically closed field of characteristic two, let A4A_4 be an alternating group on four letters, and let HH be the unique Sylow two-subgroup of A4A_4. Let XX be a smooth projective irreducible curve over kk with a faithful A4A_4-action such that the quotient curve X/HX/H is a projective line and the HH-cover XX/HX\to X/H is totally ramified, in the sense that it is ramified and every branch point is totally ramified. Under these assumptions, we determine the precise kA4kA_4-module structure of the space of holomorphic differentials of XX over kk. We show that there are infinitely many different isomorphism classes of indecomposable kA4kA_4-modules that can occur as direct summands, and we give precise formulas for the multiplicities with which they occur.

Keywords

Cite

@article{arxiv.2510.15743,
  title  = {Holomorphic differentials of alternating four covers},
  author = {Frauke M. Bleher and Margarita Bustos Gonzalez},
  journal= {arXiv preprint arXiv:2510.15743},
  year   = {2025}
}

Comments

38 pages; appendix on indecomposable modules in characteristic 2

R2 v1 2026-07-01T06:43:30.647Z