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 non-dissipative 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 ($T_c$), 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.