We show the existence of a left invariant pseudo-Riemannian metric on the O
scillator Group of dimension four, such that this group becomes a space-tim
e with singularities in the sense of Hawking and Penrose. As an application
we exhibit new incomplete, nonhomeomorphic compact Lorentzian manifolds. (
C) 2000 American Institute of Physics. [S0022-2488(00)01612-1].