English

On $p$-gonal fields of definition

Algebraic Geometry 2022-02-28 v1

Abstract

Let SS be a closed Riemann surface of genus g2g \geq 2 and φ\varphi be a conformal automorphism of SS of prime order pp such that S/φS/\langle \varphi \rangle has genus zero. Let KC{\mathbb K} \leq {\mathbb C} be a field of definition of SS. We provide an argument for the existence of a field extension F{\mathbb F} of K{\mathbb K}, of degree at most 2(p1)2(p-1), for which SS is definable by a curve of the form yp=F(x)F[x]y^{p}=F(x) \in {\mathbb F}[x], in which case φ\varphi corresponds to (x,y)(x,e2πi/py)(x,y) \mapsto (x,e^{2 \pi i/p} y). If, moreover, φ\varphi is also definable over K{\mathbb K}, then F{\mathbb F} can be chosen to be at most a quadratic extension of K{\mathbb K}. For p=2p=2, that is when SS is hyperelliptic and φ\varphi is its hyperelliptic involution, this fact is due to Mestre (for even genus) and Huggins and Lercier-Ritzenthaler-Sijslingit in the case that Aut(S)/φ{\rm Aut}(S)/\varphi\rangle is non-trivial.

Keywords

Cite

@article{arxiv.2202.12668,
  title  = {On $p$-gonal fields of definition},
  author = {Ruben A. Hidalgo},
  journal= {arXiv preprint arXiv:2202.12668},
  year   = {2022}
}

Comments

arXiv admin note: text overlap with arXiv:1309.6904