Generators and splitting fields of certain elliptic K3 surfaces (2206.05372v2)

Abstract: Let $k \subset {\mathbb C}$ be a number field and ${\mathcal E}$ be an elliptic curve that is isomorphic to the generic fiber of an elliptic surface defined over the rational function field $k(t)$ of the projective line ${\mathbb P}^1_k$. The set ${\mathcal E}(K)$ of $K$-rational points of ${\mathcal E}$ is known to be a finitely generated abelian group for any subfield $K$ of ${\mathbb C}(t)$. The splitting field of ${\mathcal E}$ over $k(t)$ is the smallest subfield ${\mathcal K}$ of ${\mathbb C}$ which is a finite extension of $k$ and ${\mathcal E} ({\mathbb C} (t)) ={\mathcal E} ({\mathcal K}(t))$. In this paper, we consider the elliptic $K3$ surfaces defined over $k={\mathbb Q}$ with the generic fiber given by the Weierstrass equation ${\mathcal E}_n: \displaystyle y^2=x^3 + t^n + 1/t^n.$ We will determine the splitting field ${\mathcal K}_n$ and find an explicit set of independent generators for ${\mathcal E}_n ({\mathcal K_n}(t))$ for $1\leq n \leq 6$.