On the dimension drop for harmonic measure on uniformly non-flat Ahlfors-David regular boundaries

Abstract

We extend earlier results of Azzam on the dimension drop of the harmonic measure for a domain $\Omega \subset {\mathbb{R}}^n$ with $n\ge 3$, with dimensional Ahlfors regular boundary $\partial \Omega$ of dimension $s$ with $n-1-{\delta }_0\le s\le n-1$, that is uniformly non flat. Here ${\delta }_0$ is a small positive constant dependent on the parameters of the problem. Our novel construction relies on elementary geometric and potential theoretic considerations. We avoid the use of Riesz transforms and compactness arguments, and also give quantitative bounds on the ${\delta }_0$ parameter.

Corrected some minor issues; added a table in the notation section