Relativistic heavy ion physics: a theoretical overview
  This is a mini-review of recent theoretical work in the field of relativistic heavy ion physics. The following topics are discussed: initial conditions and the Color Glass Condensate; approach to thermalization and the hydrodynamical evolution; hard probes and the properties of the Quark-Gluon Plasma. Some of the unsolved problems and potentially promising directions for future research are listed as well. 
D. Kharzeev