English

Moduli of certain wild covers of curves

Algebraic Geometry 2019-08-13 v3

Abstract

A fine moduli space is constructed, for cyclic-by-p\mathsf{p} covers of an affine curve over an algebraically closed field kk of characteristic p>0\mathsf{p}>0. An intersection of finitely many fine moduli spaces for cyclic-by-p\mathsf{p} covers of affine curves gives a moduli space for p\mathsf{p}'-by-p\mathsf{p} covers of an affine curve. A local moduli space is also constructed, for cyclic-by-p\mathsf{p} covers of Spec(k((x)))Spec(k((x))), which is the same as the global moduli space for cyclic-by-p\mathsf{p} covers of P1{0}\mathbb{P}^1-\{0\} tamely ramified over \infty with the same Galois group. Then it is shown that a restriction morphism is finite with degrees on connected components p\mathsf{p} powers: There are finitely many deleted points of an affine curve from its smooth completion. A cyclic-by-p\mathsf{p} cover of an affine curve gives a product of local covers with the same Galois group of the punctured infinitesimal neighbourhoods of the deleted points. So there is a restriction morphism from the global moduli space to a product of local moduli spaces.

Keywords

Cite

@article{arxiv.1904.03763,
  title  = {Moduli of certain wild covers of curves},
  author = {Jianru Zhang},
  journal= {arXiv preprint arXiv:1904.03763},
  year   = {2019}
}

Comments

some typos corrected and minor changes made