At high energies, or equivalently small momentum fraction x, the nonlinearity of QCD makes the theory nonperturbative even at weak coupling. In this regime the properties of a hadron or nucleus are most conveniently described by QCD in the effective theory framework known as the Color Glass Condensate. The collision of two such systems, as at RHIC or heavy ion collisions at the LHC, leads to a classical field “glasma” description of the initial stage of the collision. This talk will review some features of the glasma and discuss applications to RHIC and LHC phenomenology. Also described will be ongoing work to go beyond the leading classical order and the relation of these NLO corrections to plasma instabilities, isotropization and eventual thermalization of the collision system.

SPhT, CEA/Saclay