中国科学院数学与系统科学研究院
数学研究所
数学科学全国重点实验室
拓扑研讨班
Speaker: 沙熠（北京大学）
Inviter: 苏阳
Language: English
Title: Nielsen Realization Problem and Homotopy Coherent Action
Time & Venue: 2026年9月21日（星期一） 14:30-15:00 南楼N820
Abstract: The Nielsen realization problem asks whether finite subgroups of mapping class groups can be realized as genuine group actions on manifolds. From a homotopy-theoretic perspective, we can consider the more flexible notion of a homotopy coherent action instead of a genuine action. It is natural to ask whether a subgroup could be realized by a homotopy coherent action when it fails to be realized as a genuine action. In this talk, I will first survey recent progress on these questions and then present our result on K3-type 4-manifolds. Our main tool is family Seiberg–Witten invariants. This is joint work with Yujie Lin.