$\sqrt{-3}$-Selmer groups, ideal class groups and large $3$-Selmer ranks

Fuente: arXiv
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Autori principali: Jha, Somnath, Majumdar, Dipramit, Shingavekar, Pratiksha
Natura: Preprint
Pubblicazione: 2025
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author Jha, Somnath
Majumdar, Dipramit
Shingavekar, Pratiksha
author_facet Jha, Somnath
Majumdar, Dipramit
Shingavekar, Pratiksha
contents We consider the family of elliptic curves $E_{a,b}:y^2=x^3+a(x-b)^2$ with $a,b \in \mathbb{Z}$. These elliptic curves have a rational $3$-isogeny, say $φ$. We give an upper and a lower bound on the rank of the $φ$-Selmer group of $E_{a,b}$ over $K:=\mathbb{Q}(ζ_3)$ in terms of the $3$-part of the ideal class group of certain quadratic extension of $K$. Using our bounds on the Selmer groups, we construct infinitely many curves in this family with arbitrary large $3$-Selmer rank over $K$ and no non-trivial $K$-rational point of order $3$. We also show that for a positive proportion of natural numbers $n$, the curve $E_{n,n}/\mathbb{Q}$ has root number $-1$ and $3$-Selmer rank $=1$.
format Preprint
id arxiv_https___arxiv_org_abs_2502_01069
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle $\sqrt{-3}$-Selmer groups, ideal class groups and large $3$-Selmer ranks
Jha, Somnath
Majumdar, Dipramit
Shingavekar, Pratiksha
Number Theory
We consider the family of elliptic curves $E_{a,b}:y^2=x^3+a(x-b)^2$ with $a,b \in \mathbb{Z}$. These elliptic curves have a rational $3$-isogeny, say $φ$. We give an upper and a lower bound on the rank of the $φ$-Selmer group of $E_{a,b}$ over $K:=\mathbb{Q}(ζ_3)$ in terms of the $3$-part of the ideal class group of certain quadratic extension of $K$. Using our bounds on the Selmer groups, we construct infinitely many curves in this family with arbitrary large $3$-Selmer rank over $K$ and no non-trivial $K$-rational point of order $3$. We also show that for a positive proportion of natural numbers $n$, the curve $E_{n,n}/\mathbb{Q}$ has root number $-1$ and $3$-Selmer rank $=1$.
title $\sqrt{-3}$-Selmer groups, ideal class groups and large $3$-Selmer ranks
topic Number Theory
url https://arxiv.org/abs/2502.01069