It is shown that a semiquantitative understanding of the properties liquid helium is possible in terms of a simple parametrization of the effective helium-helium interaction and of its temperature and density dependence. Some properties of the effective interaction are discussed within the framework of the temperature-dependent Green's-function formalism and the difficulties connected with the extension of the approach to more elaborate situations are briefly indicated.

• Received 5 November 1974

DOI:https://doi.org/10.1103/PhysRevB.12.134