Structure of the Ground State of a Fermion Fluid

Variational many-body wave functions for the ground state of liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ which include triplet and backflow correlations are investigated with use of Monte Carlo integration. Our energy of - 1.9°K removes half of the discrepancy between previous Jastrow-Slater calculations and experimental results. The first exact results for mass-three bosons are also presented. Triplet correlations in the variational wave function are equally effective in lowering the energy of both mass-three bosons and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$.