Talk:Keldysh formalism

This definition "In condensed matter physics, the Keldysh formalism describes the evolution of quantum mechanical states in the presence of a time varying magnetic field" is far from being complete. First, it is not limited to condensed matter physics. The formalism is applicable to any quantum mechanical system out of equilibrium. Second, it can be applied to systems with time varying magnetic fields but it cannot be limited to only this case.