The cosmological singularity problem

Despite impressive phenomenological successes, cosmological models are incomplete without an understanding of what happened at the big bang singularity. Depending on the model, one would like to understand how appropriate initial conditions were selected at the big bang singularity, or how a pre-existing contracting universe underwent a big crunch/big bang transition, if such transitions are possible at all. In this talk, after an introduction to these questions, an attempt is described to study cosmological singularities using the AdS/CFT correspondence. A specific model in which asymptotically AdS initial data evolve into a big crunch singularity is discussed and a dual field theory description is provided.