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arXiv · 1305.1698

Poisson deformations and birational geometry

Yoshinori Namikawa
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Abstract

Let π: Y -> X be a crepant projective resolution of an affine symplectic variety X with a good C^*-action. We interpret the second cohomology H^2(Y, C) in two ways. First, H^2(Y, C) is the Picard group of Y tensorised with C. By the ample cones of different crepant resolutions of X, there is a natural chamber structure in H^2(Y, C). The second interpretation of H^2(Y, C) is the base space of the universal Poisson deformation $\mathcal Y$ of Y. Let D \subset H^2(Y, C) be the locus where the corresponding Poisson varieties are not affine. Then D is the union of finite number of hyperplanes, which gives a chamber structure in H^2(Y, C). These two chamber structures coincide.

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Yoshinori Namikawa. 2014-04-06. Poisson deformations and birational geometry. https://arxiv.org/abs/1305.1698

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