Semi-group compactifications of Algebraic Groups

Abstract

We show that for algebraic groups over local fields of characteristic zero, the following are equivalent: Every homomorphism has a closed image, every unitary representation decomposes into a direct sum of finite-dimensional and mixing representations, and that the matrix coefficients are dense within the algebra of weakly almost periodic functions over the group. In our proof, we employ methods from semi-group theory. We establish that algebraic groups are \emph{compactification-centric}, meaning $sG=Gs$ for any element $s$ in the weakly almost periodic compactification of the group $G$.