Normal closures of mapping classes

Geometry Topology Seminar
Tuesday, June 20, 2017 - 14:05
1 hour (actually 50 minutes)
Skiles 006
Georgia Tech
We give a simple geometric criterion for an element to normally generate the mapping class group of a surface. As an application of this criterion, we show that when a surface has genus at least 3, every periodic mapping class except for the hyperelliptic involution normally generates. We also give examples of pseudo-Anosov elements that normally generate when genus is at least 2, answering a question of D. Long.