Degenerations of (1,7)-polarized abelian surfaces

Abstract

The moduli space of (1,7)-polarized abelian surfaces with a level structure was shown by Manolache and Schreyer to be rational with compactification a Fano 3-fold of genus 12 which is also a compactification of the variety of powersum presentations of the Klein quartic curve. In this paper the possible degenerations of the abelian surfaces are classified in terms of degenerations of powersum presentations. In particular, the surface degenerations into fourteen planes are recovered. These were independently discovered by Alfio Marini using degenerations of twisted cubic curves.