Speaker:
Thomas Kraemer

10.00--11.00 in S79

Title:
A converse to Riemann's theorem on Jacobian varieties

Abstract:
Jacobians of curves have been studied a lot since Riemann's theorem
which says that their theta divisor is a sum of copies of the curve.
Similarly, for intermediate Jacobians of smooth cubic threefolds Clemens
and Griffiths showed that the theta divisor is a sum of two copies of
the Fano surface. We prove that in both cases these are the only
decompositions, generalizing results of Casalaina-Martin, Popa and
Schreieder. Our ideas apply to a much wider context, they only rely on
the decomposition theorem for perverse sheaves and some representation
theory.