The automorphism group of torsion points of an elliptic curve over a field of characteristic $\ge 5$

Fuente: arXiv
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Main Authors: Im, Bo-Hae, Kim, Hansol
Format: Preprint
Published: 2025
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author Im, Bo-Hae
Kim, Hansol
author_facet Im, Bo-Hae
Kim, Hansol
contents For a field $\mathbb{K}$ of characteristic $p\ge5$ containing $\mathbb{F}_{p}^{\operatorname{alg}}$ and the elliptic curve $E_{s,t}: y^{2} = x^{3} + sx + t$ defined over the function field $\mathbb{K}\left(s,t\right)$ of two variables $s$ and $t$, we prove that for a non-negative positive integer $e$ and a positive integer $N$ which is not divisible by $p$, the automorphism group of the normal extension $\mathbb{K}\left(s,t\right)\left(E_{s,t}\left[p^{e} N\right]\right)$ over $\mathbb{K}\left(s,t\right)$ is isomorphic to $\left(\mathbb{Z}/p^{e}\mathbb{Z}\right)^{\times} \times \operatorname{SL}_{2} \left(\mathbb{Z}/N\mathbb{Z}\right)$.
format Preprint
id arxiv_https___arxiv_org_abs_2504_14859
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The automorphism group of torsion points of an elliptic curve over a field of characteristic $\ge 5$
Im, Bo-Hae
Kim, Hansol
Number Theory
14H52
For a field $\mathbb{K}$ of characteristic $p\ge5$ containing $\mathbb{F}_{p}^{\operatorname{alg}}$ and the elliptic curve $E_{s,t}: y^{2} = x^{3} + sx + t$ defined over the function field $\mathbb{K}\left(s,t\right)$ of two variables $s$ and $t$, we prove that for a non-negative positive integer $e$ and a positive integer $N$ which is not divisible by $p$, the automorphism group of the normal extension $\mathbb{K}\left(s,t\right)\left(E_{s,t}\left[p^{e} N\right]\right)$ over $\mathbb{K}\left(s,t\right)$ is isomorphic to $\left(\mathbb{Z}/p^{e}\mathbb{Z}\right)^{\times} \times \operatorname{SL}_{2} \left(\mathbb{Z}/N\mathbb{Z}\right)$.
title The automorphism group of torsion points of an elliptic curve over a field of characteristic $\ge 5$
topic Number Theory
14H52
url https://arxiv.org/abs/2504.14859