Extension theorems for differential forms and Bogomolov-Sommese vanishing on log canonical varieties

Daniel Greb, Stefan Kebekus, Sándor J. Kovács

Published 2008-08-27, updated 2009-04-27Version 3

Given a p-form defined on the smooth locus of a normal variety, and a resolution of singularities, we study the problem of extending the pull-back of the p-form over the exceptional set of the desingularization. For log canonical pairs and for certain values of p, we show that an extension always exists, possibly with logarithmic poles along the exceptional set. As a corollary, it is shown that sheaves of reflexive differentials enjoy good pull-back properties. A natural generalization of the well-known Bogomolov-Sommese vanishing theorem to log canonical threefold pairs follows.