Capitulation discriminants of genus one curves

Abstract

In this paper we study the arithmetic and invariant theory of genus one normal curves embedded in $\mathbb{P}^{n-1}$. We generalize the notion of genus one model of degree $n$, introduced by Cremona, Fisher and Stoll for $n \leq 5$, to arbitrary odd $n$, and describe the invariant theory of a genus one curve of degree $n$ embedded in $ \mathbb{P}^{n-1}$ in terms of the minimal graded free resolution of its homogeneous ideal. We prove that everywhere locally soluble genus one curves over $ \mathbb{Q}$ admit minimal integral models, with the same invariants as those of the minimal model of their Jacobian elliptic curve. We then apply these results to study the capitulation problem for the Tate-Shafarevich group of an elliptic curve $E/\mathbb{Q}$. We prove that every element of $\text{Sha}(E/\mathbb{Q})[n]$ of odd index $n$ splits over a degree $n$ number field $K$, of absolute discriminant at most $c(n) H_E^{2n-2}$, where $H_E$ is the naive height of $E$ and $c(n)$ is a constant only depending on $n$.