Phase ordering kinetics 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 nondissipative Josephson precession term in driving the system to a new universality class. A model of coarsening in dimension d52, involving a quench between two temperatures below the equilibrium superfluid transition temperature (Tc), is exactly solved and demonstrates the relevance of the Josephson term. Numerical results on quenches from above Tc in d52,3 provide evidence for the scaling picture postulated. @S1050-2947~96!07408-2#