58:14
publiée le 30 octobre 2025
Equivariant trisections for group actions on four-manifolds
De Jeffrey Meier
Claspers, graspers, barbells
Apparaît dans la collection : Jean Morlet Chair - Trisections and related topics / Chaire Jean Morlet - Trisections et interactions
Infinite lists of non-isotopic and independent diffeomorphisms of S^1 x S^3 have been constructed by Budney and Gabai using barbells, and by Watanabe using claspers. In this talk I will explain how barbells can be obtained from families of dancing circles, called graspers. This perspective is powerful in certain settings, where it provides quick proofs of existence of infinite subgroups of mapping class groups.
