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.