Theta divisors with curve summands and the Schottky problemStefan Schreieder
We prove the following converse of Riemann's Theorem: Let (A,\Theta) be an indecomposable principally polarized abelian variety whose theta divisor can be written as a sum of a curve and a codimension two subvariety \Theta=C+Y. Then C is smooth, A is the Jacobian of C, and Y is a translate of W_{g2}(C). As applications, we solve the DPC Problem for theta divisors and characterize Jacobians by the existence of a ddimensional subvariety with curve summand whose twisted ideal sheaf is a GVsheaf. Document Actions 
