Higher dimensional Kleinian groups of small Hausdorff dimension are classical Schottky groups II

Abstract

This is the higher dimensional continuation of our works on Hausdorff dimension of Kleinian groups \cite{Hou2010}, \cite{Hou2020}. In this paper we prove that for all $r\ge 2$ there exists $λ_r>0$, which is independent of the dimension $N$ of the hyperbolic space, such that any finitely generated non-elementary torsion-free Kleinian group of $\Isom(\mathbb{H}^N)$ generated by $r$ elements with limit set of Hausdorff dimension $<λ_r$ is a classical Schottky group. For two generators the bound can be taken to be $1/3$. The proof relies on our previous works in \cite{Hou2010}, \cite{Hou2020} and on a metric carrier graph reduction. Our result can also be considered as the complete converse to the well-known theorem of Phillips-Sarnak \cite{PS} for spaces of any dimension $N$.