The dualizing sheaf on first-order deformations of toric surface singularities

Abstract

We explicitly describe infintesimal deformations of cyclic quotient singularities that satisfy one of the deformation conditions introduced by Wahl, Kollár-Shepherd-Barron and Viehweg. The conclusion is that in many cases these three notions are different from each other. In particular, we see that while the KSB and the Viehweg versions of the moduli space of surfaces of general type have the same underlying reduced subscheme, their infinitesimal structures are different.

The introduction has been expanded. Moreover, we have corrected a couple of misprints and a mistake in the quotation of the T1 formula