## 幾何学コロキウム: Cohomology of the moduli space of graphs and groups of homology cobordisms of surfaces　（逆井卓也氏　東大数理）

2017年 　 11月 10日 16時 30分 ～ 2017年 　 11月 10日 18時 00分

3-204

Abstract: We construct an abelian quotient of the symplectic
derivation Lie algebra of the free Lie algebra generated by the
fundamental representation of the symplectic group. It gives an
alternative proof of the fact first shown by Bartholdi that the top
rational homology group of the moduli space of metric graphs of rank 7
is one dimensional. As an application, we construct a non-trivial
abelian quotient of the homology cobordism group of a surface of
positive genus. This talk is based on joint works with Shigeyuki
Morita, Masaaki Suzuki and Gwénaël Massuyeau.

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