Affine transformations and parallel lightlike vector fields on compact Lorentzian -manifolds
arXiv:1404.1357
Abstract
We describe the compact Lorentzian -manifolds admitting a parallel lightlike vector field. The classification of compact Lorentzian -manifolds admitting non-isometric affine diffeomorphisms follows, together with the complete description of these morphisms. Such a Lorentzian manifold is in some sense an equivariant deformation of a flat one.
37p