Deformations of group actions
arXiv:math/0407417
Abstract
Let be a noncompact real algebraic group and $\G<G$ a lattice. One purpose of this paper is to show that there is an smooth, volume preserving, mixing action of or $\G$ on a compact manifold which admits a smooth deformation. We also describe some other, rather special, deformations when and provide a simple proof that any action of a compact Lie group is locally rigid.
Slight revision. A few clarifications made, one reference added