  In this work we introduce a concept of expansiveness for actions of connected
Lie groups. We study some of its properties and investigate some implications
of expansiveness. We study the centralizer of expansive actions. We investigate
the geometric entropy of expansive foliations and prove that any expansive
locally-free action of a connected Lie group on a closed manifold has positive
geometric entropy. We also study these problems for actions of finely generated
groups.
