arXiv subjects

A. Silverberg

Publications and source records attributed to A. Silverberg.

20 records · Page 2Linked to original sources

arXiv1996

Images of $\ell$-adic representations and automorphisms of abelian varieties

Suppose $F$ is either a global field or a finitely generated extension of ${\mathbf Q}$, $A$ is an abelian variety over $F$, and $\ell$ is a prime not equal to the characteristic of $F$. Let $Z$ denote the center of the endomorphism algebra of $A$. Let $G$ denote the group of ${\mathbf Q}_\ell$-points of the identity connected component of the Zariski closure of the image of the $\ell$-adic representation associated to $A$. We prove the $\ell$-independence of the intersection of $G$ with the torsion subgroup of $Z$. Our results provide evidence in the direction of the Mumford-Tate Conjecture.

alg-geom↗

arXiv1995

Hodge groups of abelian varieties with purely multiplicative reduction

The main result of the paper is that if $A$ is an abelian variety over a subfield $F$ of ${\bold C}$, and $A$ has purely multiplicative reduction at a discrete valuation of $F$, then the Hodge group of $A$ is semisimple. Further, we give necessary and sufficient conditions for the Hodge group to be semisimple. We obtain bounds on certain torsion subgroups for abelian varieties which do not have purely multiplicative reduction at a given discrete valuation, and therefore obtain bounds on torsion for abelian varieties, defined over number fields, whose Hodge groups are not semisimple.

alg-geom↗