By the inspirational works of Peter Sarnak and Ralph Phillips (ACTA 1985), we know that all classical Schottky groups (dim n >3) must have Hausdorff dimension strictly bounded away from dim n-1. Later Peter Doyle (ACTA 1988) showed that it is also true for n=3.
The local topology of isolated complex surface singularites is long understood, as cones on closed 3-manifolds obtained by negative definite plumbing.
University of Texas at Austin
University of Warsaw
This is a joint Topology - Algebraic Topology seminar.
University of Edinburgh