Identifying central endomorphisms of an abelian variety via Frobenius endomorphisms

Abstract

Assuming the Mumford-Tate conjecture, we show that the center of the endomorphism ring of an abelian variety defined over a number field can be recovered from an appropriate intersection of the fields obtained from its Frobenius endomorphisms. We then apply this result to exhibit a practical algorithm to compute this center.

12 pages, minor revision