On Extremal Contractions from Threefolds to Surfaces: the Case of One non-Gorenstein Point

Abstract

Let $f:X\to S$ be an extremal contraction from a threefold with only terminal singularities to a surface. We study local analytic structure such contractions near degenerate fiber $C$ in the case when $C$ is irreducible and $X$ has on $C$ only one non-Gorenstein point.

arXiv commentLaTeX2e, to appear in Contemporary Math. AMS