On the Hydrodynamical Model for a Bose Liquid at T=0

This paper is essentially an extension of the work of Josephson to deal with effects due to spatial variations in the local density. We formulate the theory for an interacting Bose system in terms of the functional integration in the space of complex fields. by introducing the ε-term, a modification of the generating functional is given. It is shown how we can beyond the pole approximation by Josephson.