Closed strings in Misner space: a toy model for a Big Bounce ?
  Misner space, also known as the Lorentzian orbifold $R^{1,1}/boost$, is one of the simplest examples of a cosmological singularity in string theory. In this lecture, we review the semi-classical propagation of closed strings in this background, with a particular emphasis on the twisted sectors of the orbifold. Tree-level scattering amplitudes and the one-loop vacuum amplitude are also discussed. 
Bruno Durin (LPTHE), Boris Pioline (LPTHE, LPTENS)