Geometry and Topology Seminar——Extendability over the 4-sphere and invariant spin structures of surface automorphisms
报告人：王炜飚（英国威廉希尔公司）
时间：2023-05-17 13:00-15:00
地点：Room 1114, Sciences Building No. 1
Abstract: Shicheng Wang and Zhongzi Wang showed that for an automorphism f of an oriented closed surface, if and only if f has a bounding invariant spin structure, we can embed the surface in the 4-sphere such that f extends to an automorphism of the 4-sphere. Using this criterion, for each oriented closed surface of genus g>1 except for g=4, we construct a period-8 map that is never extendable over the 4-sphere. We also show that each surface automorphism has an invariant spin structure. As a consequence, every surface automorphism is extendable over the 4-sphere after a stabilization. It is joint work with Zhongzi Wang.
