Far from equilibrium dynamics of the Bose gas

We study the approach to equilibrium of a Bose gas to a superfluid state. We point out that dynamic scaling, characteristic of far from equilibrium phase-ordering systems, should hold. We stress the importance of a non-dissipative Josephson precession term in driving the system to a new universality class. A model of coarsening in d=2, involving a quench between two temperatures below the equilibrium superfluid transition temperature (T_c), is exactly solved and demonstrates the relevance of the Josephson term. Numerical results on quenches from above T_c in d=2,3 provide evidence for the scaling picture postulated.