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 d=2, 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 d=2,3 provide evidence for the scaling picture postulated. {} 1996 The American Physical Society.