Ross Geoghegan, SUNY Binghamton

Abstract: Let G be a discrete group and let R be a commutative ring.Assume we are given:
1. An RG-module A
2. A proper CAT(0) metric space M
3. An action of G on M by isometries

There is an interesting interplay between the module A and the G-action on M. It involves the existence or non-existence of R-generating sets for A which "lie over" desirable subsets of M such as balls or horoballs. In this talk I'll only discuss the simplest level (the 0th) of a theory which has a level for each n.