A result on the birational map between two normal 3-folds (Q1192396)

The author studies crepant morphisms of algebraic threefolds. The main result of the paper (corollary 2, \S2) states that a birational map \(f:X\to Y\), of normal threefolds \(X\) and \(Y\) with only terminal singularities is always an isomorphism in codimension one, provided the canonical class \(K_ Y\) is nef. This result is obtained as a consequence of some results of \textit{Miles Reid} (resp. the \textit{weak index theorem}) and of some transitive properties of crepancy, proved by the author (see \S2).