Les groupes oscillateurs et leurs reseaux

In this paper we study the geometry of oscillator groups: they are the only non commutative simply connected solvable Lie groups which have a biinvariant Lorentzian metric. We first study curvature and geodesics, and then give a full analysis of lattices - i.e. discrete co-compact subgroups - getting examples of compact Lorentzian homogeneous varieties.