Generators and splitting fields of certain elliptic $K3$ surfaces
Journal de théorie des nombres de Bordeaux, Tome 38 (2026) no. 2, pp. 317-339

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

Soit $k \subset {\mathbb{C}}$ un corps de nombres et $\mathcal{E}$ une courbe elliptique définie sur $k(t)$ qui est isomorphe à la fibre générique d’une surface elliptique $\pi : \mathcal{S}_{\mathcal{E}} \rightarrow {\mathbb{P}}^1_k$. Pour tout sous-corps $\mathcal{K}\subseteq {\mathbb{C}}$ de $k$, l’ensemble $\mathcal{E}(\mathcal{K}(t))$ des points rationnels de $\mathcal{E}$ est un groupe abélien de type fini. Le corps de décomposition de $\mathcal{E}$ défini sur $k(t)$ est la plus petite extension finie $\mathcal{K} \subset {\mathbb{C}}$ de $k$ telle que $\mathcal{E} ({\mathbb{C}} (t)) \cong \mathcal{E} (\mathcal{K}(t))$. Dans cet article, nous considérons les surfaces elliptiques $K3$ définies sur $k={\mathbb{Q}}$ de fibre générique donnée par l’équation de Weierstrass $\mathcal{E}_n : \displaystyle y^2=x^3 + t^n + 1/t^n$, $1\le n\le 6$, déterminons le corps de décomposition $\mathcal{K}_n$ et trouvons un ensemble explicite de générateurs linéairement indépendants pour $\mathcal{E}_n (\mathcal{K_n}(t))$ pour $1 \le n \le 6$.

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DOI : 10.5802/jtnb.1363
Classification : 14J27, 11G05
Keywords: Elliptic surface, Mordell–Weil lattice, Splitting field

Sajad Salami  1   ; Arman Shamsi Zargar  2

1 Institute of Mathematics and Statistics, State University of Rio de Janeiro, Rio Janeiro, RJ, Brazil
2 Department of Mathematics and Applications, Faculty of Mathematical Sciences, University of Mohaghegh Ardabili, Ardabil, Iran
Licence : CC-BY-ND 4.0
Droits d'auteur : Les auteurs conservent leurs droits
Sajad Salami; Arman Shamsi Zargar. Generators and splitting fields of certain elliptic $K3$ surfaces. Journal de théorie des nombres de Bordeaux, Tome 38 (2026) no. 2, pp. 317-339. doi: 10.5802/jtnb.1363
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