Rational torsion points on abelian surfaces with quaternionic multiplication

Let A be an abelian surface over ${\mathbb {Q}}$ whose geometric endomorphism ring is a maximal order in a non-split quaternion algebra. Inspired by Mazur’s theorem for elliptic curves, we show that the torsion subgroup of $A({\mathbb {Q}})$ is $12$ -torsion and has order at most...

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Bibliographic Details
Published in:Forum of Mathematics, Sigma
Main Authors: Jef Laga, Ciaran Schembri, Ari Shnidman, John Voight
Format: Article
Language:English
Published: Cambridge University Press 2024-01-01
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Online Access:https://www.cambridge.org/core/product/identifier/S2050509424001051/type/journal_article
Description
Summary:Let A be an abelian surface over ${\mathbb {Q}}$ whose geometric endomorphism ring is a maximal order in a non-split quaternion algebra. Inspired by Mazur’s theorem for elliptic curves, we show that the torsion subgroup of $A({\mathbb {Q}})$ is $12$ -torsion and has order at most $18$ . Under the additional assumption that A is of $ {\mathrm{GL}}_2$ -type, we give a complete classification of the possible torsion subgroups of $A({\mathbb {Q}})$ .
ISSN:2050-5094