G\"odel's universe and the chronology protection conjecture
  We present a solution for the geodesic motion in G\"odel's universe that provides a particular proof of Hawking's chronology protection conjecture in three-dimensional gravity theory. The solution is based upon the fact that the group of the automorphisms of the Heisenberg motion group H1\timesU(1), modulo discrete sub-group Z, act isometrically on the boundary of the hyperbolic three-dimensional manifold. Closed timelike curves do not exist due to the presence of a closed Cauchy-Riemann surface for chronology protection, with two mirror symmetric sets of helicoidal self-similar modules inside. The present solution is isometrically equivalent to a cylindrical gravitational monochromatic wave front. 
P. Pitanga
gr-qc