  We prove that the conformal group of a closed, simply connected, real
analytic Lorentzian manifold is compact. D'Ambra proved in 1988 that the
isometry group of such a manifold is compact. Our result implies the Lorentzian
Lichnerowicz Conjecture for real analytic Lorentzian manifolds with finite
fundamental group.
  Third version includes corrections and clarifications, particularly in
section 6.
