The one percent property for free groups

Abstract

We prove that for every $\varepsilon >0$, there is $δ>0$ such that for every probability measure $μ$ on a free group $\mathbb{F}$, if the operator norm of the action of $μ$ on $L^2\mathbb{F}$ by convolution exceeds $\varepsilon$, then there is a coset of an abelian subgroup of $\mathbb{F}$ with $μ$-mass at least $δ$.