English

A local-global principle for polyquadratic twists of abelian surfaces

Number Theory 2024-01-26 v2

Abstract

We say that two abelian varieties AA and AA' defined over a field FF are polyquadratic twists if they are isogenous over a Galois extension of FF whose Galois group has exponent dividing 22. Let AA and AA' be abelian varieties defined over a number field KK of dimension g1g\geq 1. In this article we prove that, if g2g\leq 2, then AA and AA' are polyquadratic twists if and only if for almost all primes \p\p of KK their reductions modulo \p\p are polyquadratic twists. We exhibit a counterexample to this local-global principle for g=3g=3. This work builds on a geometric analogue by Khare and Larsen, and on a similar criterion for quadratic twists established by Fit\'e, relying itself on the works by Rajan and Ramakrishnan.

Keywords

Cite

@article{arxiv.2210.06317,
  title  = {A local-global principle for polyquadratic twists of abelian surfaces},
  author = {Francesc Fité and Antonella Perucca},
  journal= {arXiv preprint arXiv:2210.06317},
  year   = {2024}
}

Comments

17 pages. To appear in Indiana University Mathematics Journal. Mild expository changes