On the classification of crepant analytically extremal contractions of smooth three-folds

[摘要] We discuss the problem of classifying crepant analytically extremal contractions $X o Y$ from a smooth 3-fold, contracting an irreducible normal divisor D in X to a point P in Y. We prove that, if D has degree $(-K_D)^2 geq 5$, the analytic structure of the contraction is completely determined by the isomorphism class of the exceptional locus and its normal bundle. This was previously known only for a smooth exceptional locus D.

[学科分类] 数学（综合）