The Tannakian Schottky Conjecture in Genus Five

Abstract

Using the Tannakian formalism, one can attach to a principally polarized abelian variety a reductive group, along with a representation. We show that this group and the representation characterize Jacobians in genus up to $5$. More generally, our results hold on the bielliptic Prym locus in all genera. This gives the first evidence towards a recent conjecture by Weissauer and Kr\"amer. The main tool in our proof is a criterion for detecting Jacobians relying on Chern-Mather classes.