Rank gradient in co-final towers of certain Kleinian groups

Abstract

We prove that if the fundamental group of an orientable finite volume hyperbolic 3-manifold has finite index in the reflection group of a right-angled ideal polyhedra in ${\mathbb{H}}^3$ then it has a co-final tower of finite sheeted covers with positive rank gradient. The manifolds we provide are also known to have co-final towers of covers with zero rank gradient.

15 pages, 2 figures

References in corpus (1)

• Rank gradient, cost of groups and the rank versus Heegaard genus problem