Shimura varieties and abelian covers of the line

Abstract

We prove that under some conditions on the monodromy, families of abelian covers of the projective line do not give rise to (higher dimensional) Shimura subvarieties in $A_g$. This is achieved by a reduction to $p$ argument. We also use another method based on monodromy computations to show that two dimensional subvarieties in the above locus are not special. In particular it is shown that such families have usually large monodromy groups. Together with our earlier results, the above mentioned results contribute to classifying the special families in the moduli space of abelian varieties and partially completes the work of several authors including the author's previous work.

21 pages. Accepted for publication in Houston Journal of Mathematics. arXiv admin note: text overlap with arXiv:1402.1900