报告学者：林剑锋

报告者单位：清华大学

报告时间：2024年4月24日下午3：00---4：30

报告地点：8教203

报告摘要： In 2018, Watanabe disproved the 4-dimensional Smale conjecture by showing that the diffeomorphism group of a 4-dimensional disk relative to its boundary is noncontractible. A central tool in Watanabe's argument is a version of Kontsevich's characteristic classes for disk bundles, which takes value in the  homology of certain chain complexes of graphs. I will talk about the definition of graph complexes and Kontsevich's characteristic classes. And I will discuss our recent work that these invariants only  depend on formal smooth structures (i.e.,  lift of the tangent microbundle to a vector bundle).  Some applications  about moduli spaces of 4-manifolds will be given . (This is a joint work with Yi Xie.)

学者简介：林剑锋副教授，2005-2012北京大学本科及硕士；于2016在美国加州大学洛杉矶分校获得博士学位，师从天才拓扑学家 Ciprian Manolescu. 2016-2019 美国麻省理工学院讲师；2019-2021美国加州大学圣地亚哥分校助理教授；2021年至今清华大学副教授。主要从事低维拓扑领域的研究工作。