The topology of nilpotent representations in reductive groups and their maximal compact subgroups

Abstract

Let G be a complex reductive linear algebraic group and let K be a maximal compact subgroup of G. Given a nilpotent group \Gamma generated by r elements, we consider the representation spaces Hom(\Gamma,G) and Hom(\Gamma,K) with the natural topology induced from an embedding into G^r and K^r respectively. The goal of this paper is to prove that there is a strong deformation retraction of Hom(\Gamma,G) onto Hom(\Gamma,K). We also obtain a strong deformation retraction of the geometric invariant theory quotient Hom(\Gamma,G)//G onto Hom(\Gamma,K)/K.