A variational statistical mechanics of boson quantum fluids such as ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is developed as a natural generalization of the Jastrow Euler-Lagrange method which has been successfully applied to the ground-state problem. The results include a quantitative description of the liquid-gas portion of the phase diagram, including the corresponding critical point and spinodal line. Also calculated is the temperature dependence of the liquid structure function and phonon-roton spectrum within the class of trial density matrices explored in this work.

• Received 12 August 1985

DOI:https://doi.org/10.1103/PhysRevB.33.7562