Classification of extremal contractions from smooth fourfolds of <IMG ALIGN=MIDDLE HEIGHT=32 WIDTH=41>-type期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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Classification of extremal contractions from smooth fourfolds of -type

Authors:	Hiromichi Takagi

Institution:	Department of Mathematical Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-0041, Japan

Abstract:	We investigate divisorial contractions of extremal rays from smooth fourfolds. When the exceptional divisor is contracted to a curve, we prove that the divisor is a $\mathbb{P}^{2}$ -bundle or quadric bundle over a smooth curve and the contraction is the blowing up along the curve. Furthermore we determine the local analytic structure of the contraction.

Keywords:	Extremal ray contraction morphism

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