Decomposition of log crepant birational morphisms between log terminal surfaces
arXiv:math/9906143
Abstract
We prove that every log crepant birational morphism between log terminal surfaces is decomposed into log-flopping type divisorial contraction morphisms and log blow-downs. Repeating these two kinds of contractions we reach a minimal log minimal surface from any log minimal surface.
4 pages, AMSTex v2.1