[geometry-ml:04089] 東工大幾何セミナー (7/17, Zoom)

[Yoshinori Hashimoto]

皆様，

下記の要領で東工大幾何セミナーをZoom上で開催しますのでお知らせいたします．

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講演者：Nicholas Lindsay 氏（ShanghaiTech University）

日時：7月17日（金）16:30〜18:00

タイトル：Hamiltonian group actions and non-Kahler symplectic structures.

要約：There are many examples of symplectic manifolds which cannot have a Kahler structure. However, in the presence of a Hamiltonian torus action, such examples are more scarce. For example Delzant proved that if there is a Hamiltonian action of a half dimensional torus then the symplectic manifold is necessarily Kahler. Also, Karshon proved that the existence of a Hamiltonian circle action on a closed symplectic 4-manifold, implies the manifold is Kahler. For a long time, it was unknown whether a closed symplectic manifold with a Hamiltonian torus action with finite fixed point set has an invariant Kahler metric. Then, Tolman constructed a closed symplectic 6-manifold with a Hamiltonian T^2-action with 6 fixed points not having a T^2-invariant Kahler metric.
 
Recently, Goertsches, Konstantis and Zoller shows that Tolmans manifold is diffeomorphic to a projective bundle over CP^2, hence has some Kahler metric.  I will discuss a joint work with Dmitri Panov, in which we showed that the symplectic form constructed by Tolman has no compatible Kahler metric. The settles the problem of finding a compact symplectic manifold with a Hamiltonian circle action with finite fixed point set not having a compatible Kahler metric.

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Googleフォーム https://forms.gle/f1ZfmdE3EXy4Jd4y5 <https://forms.gle/f1ZfmdE3EXy4Jd4y5> にて参加登録を行います．
参加を希望される方は，7月16日（木）までに登録をお願いいたします．
セミナー当日に，登録いただいたメールアドレスにセミナーのZoom URLを送付いたします．

今後のセミナーの予定については以下をご覧ください．
http://www.math.titech.ac.jp/page_05.html <http://www.math.titech.ac.jp/page_05.html>

皆様のご参加をお待ちしております．
どうぞよろしくお願いいたします．

橋本義規
東京工業大学理学院数学系


Yoshinori Hashimoto
Department of Mathematics
Tokyo Institute of Technology
2-12-1 Ookayama, Meguro-ku,
Tokyo 152-8551
JAPAN


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