Geometry and Topology Seminar —— Topological disks, smoothing, and mapping class groups in dimension 4（1）
报告人：Cha, Jae Choon （POSTECH）
时间：2026-06-08 13:00-14:50
地点：王选报告厅（智华楼101）
【摘要】
In dimension 4, since the work of Freedman and Donaldson, it has been a highly successful area of research to investigate the differences between the topological and smooth categories in a variety of 4-dimensional settings. On the other hand, much less has been understood about when the topological and smooth cases are equivalent in dimension 4. We discuss recent results on light bulb smoothing for surfaces and “topological = smooth” for disks in 4-manifolds. We also discuss how disk smoothing allows us to transport smooth techniques to the topological category. As an application, we study structures in the mapping class groups of 4-manifolds, including non-smoothable ones.
