Kuga-Satake construction for K3 surfaces near the boundary of moduli -- Valery Alexeev, March 10, 2010
Mumford observed that the Torelli map from Mg (moduli of curves) to Ag (moduli of principally polarized abelian varieties), sending a smooth curve of genus g to its Jacobian, can be extended to a morphism between compactifications, the Deligne-Mumford compactification of Mg and a particular toroidal compactification of Ag. Namikawa showed how to make this construction geometric, and I explained how to make it functorial.
I will show that in several examples the Kuga-Satake construction, sending a K3 surface to an abelian variety, behaves in a similar way near the boundary of the respective moduli spaces.