English

Ramification of $p$-power torsion points of formal groups

Number Theory 2022-05-11 v1

Abstract

Let pp be a rational prime, let FF denote a finite, unramified extension of Qp\mathbb{Q}_p, let KK be the completion of the maximal unramified extension of Qp\mathbb{Q}_p, and let K\overline{K} be some fixed algebraic closure of KK. Let AA be an abelian variety defined over FF, with good reduction, let A\mathcal{A} denote the N\'eron model of AA over Spec(OF){\rm Spec}(\mathcal{O}_F), and let A^\widehat{\mathcal{A}} be the formal completion of A\mathcal{A} along the identity of its special fiber, i.e. the formal group of AA. In this work, we prove two results concerning the ramification of pp-power torsion points on A^\widehat{\mathcal{A}}. One of our main results describes conditions on A^\widehat{\mathcal{A}}, base changed to Spf(OK)\text{Spf}(\mathcal{O}_K) , for which the field K(A^[p])/KK(\widehat{\mathcal{A}}[p])/K is a tamely ramified extension where A^[p]\widehat{\mathcal{A}}[p] denotes the group of pp-torsion points of A^\widehat{\mathcal{A}} over OK\mathcal{O}_{\overline{K}}. This result generalizes previous work when AA is 11-dimensional and work of Arias-de-Reyna when AA is the Jacobian of certain genus 2 hyperelliptic curves.

Keywords

Cite

@article{arxiv.2205.04608,
  title  = {Ramification of $p$-power torsion points of formal groups},
  author = {Adrian Iovita and Jackson S. Morrow and Alexandru Zaharescu},
  journal= {arXiv preprint arXiv:2205.04608},
  year   = {2022}
}

Comments

15 pages, comments welcome! arXiv admin note: substantial text overlap with arXiv:2107.09165