Contractibility of boundaries of cocompact convex sets and embeddings of limit sets

Abstract

We provide sufficient conditions as to when a boundary component of a cocompact convex set in a CAT(0)-space is contractible. We then use this to study when the limit set of a quasi-convex, codimension one subgroup of a negatively curved manifold group is `wild' in the boundary. The proof is based on a notion of coarse upper curvature bounds in terms of barycenters and the careful study of interpolation in geodesic metric spaces.

arXiv comment34 pages, 1 figure. The paper has been completely rewritten. The main result is now generalised to CAT(0) spaces. A connection between lambda-barycenters and Lipschitz-extension properties has been added