Donagi-Markman cubic for Hitchin systems

Abstract

The Donagi-Markman cubic is the differential of the period map for algebraic completely integrable systems. Here we prove a formula for the cubic in the case of Hitchin's system for arbitrary $\mathfrak{g}$. This was originally stated (without proof) by Pantev for ${\mathfrak{s}l}_n$.

Final version, minor changes made at request of referee