Molecular hydrodynamics of degenerate weakly nonideal bose gas. I. Generalized equations of two-fluid hydrodynamics

The none-ideal weakly interacting Bose gas is investigated near zero temperature. On the basis of the equations, which connect the irredusible correlation functions the exact expressions for two time temperature Green's functions are obtained. In the case of weakly interacting Bose gas the interpolation formula for densty-density function is calculated suitable for arbitarary frequencies and momentum. For low frequencies the equations coincide with that of two-fluid hydrodynamics. When the wave length is less than the mean free path, the results of the usual perturbation theory for weak interaction is reproduced.The expression for superfluid velocity operator is obtained.