MOLECULAR HYDRODYNAMICS OF DEGENERATE WEAKLY NONIDEAL BOSE-GAS .1. GENERALIZED EQUATIONS OF 2-FLUID HYDRODYNAMICS

A degenerate weakly nonideal Bose gas is investigated at temperatures near zero. Relations connecting the irreducible Green's functions are used to obtain exact expressions for the two-time temperature-dependen t Green's functions. In the case of weak nonideality an expression pos sessing interpolation properties with respect to the frequency and mom entum is obtained for the density-density Green's function. At low fre quencies, the results of two-fluid hydrodynamics are reproduced. At wa velengths less than the mean free path the energy of the elementary ex citations and the damping obtained in the paper agree with the results of perturbation theory with respect to the coupling constant. An expr ession for the operator of the superfluid velocity is obtained.