Microscopic approach for dynamics of condensate near the transition temperature

A coupling between the condensate and the depletion of an interacting boson system gives rise to a frictional force on the motion of the condensate. By making use of time-dependent perturbation theory the theory for the dynamics of the condensate which reflects the character of the critical phenomena in superfluid is determined. The set of equations is the generalization of the one given by Morii et al. to include the diffusion and fluctuation terms to describe the motion of the condensate in a time-dependent calculation.