Face numbers of pseudomanifolds with isolated singularities

Isabella Novik, Ed Swartz

Published 2010-04-28Version 1

We investigate the face numbers of simplicial complexes with Buchsbaum vertex links, especially pseudomanifolds with isolated singularities. This includes deriving Dehn-Sommerville relations for pseudomanifolds with isolated singularities and establishing lower bound theorems when the singularities are also homologically isolated. We give formulas for the Hilbert function of a generic Artinian reduction of the face ring when the singularities are homologically isolated and for any pure two-dimensional complex. Some examples of spaces where the $f$-vector can be completely characterized are described. Let $\Delta$ and $\Delta'$ be two simplicial complexes that are homeomorphic and have the same $f$-vector. In \cite{MNS} the question is raised of whether or not the Hilbert functions of generic Artinian reductions of their face rings are identical. We prove that this is the case if the spaces have isolated singularities and are PL-homeomorphic.