Measure Growth in Compact Simple Lie Groups

Yifan Jing

The celebrated product theorem says if A is a generating subset of a finite simple group of Lie type G, then |AAA| \gg \min \{ |A|^{1+c}, |G| \}. In this talk, I will show that a similar phenomenon appears in the continuous setting: If A is a subset of a compact simple Lie group G, then \mu(AAA) greater than \min \{ (3+c)\mu(A), 1 \}, where \mu is the normalized Haar measure on G. I will also talk about how to use this result to solve the Kemperman Inverse Problem, and discuss what will happen when G has high dimension or when G is non-compact.

https://www.ias.edu/video/measure-growth-compact-simple-lie-groups