Bose and Fermi gases with Lennard-Jones interactions

We study a model for cold Bose and Fermi gases based on the Lennard-Jones interaction, using the optimized (Fermi-)hypernetted-chain ((F)HNC-EL) method. For comparison, we also have carried out path integral ground state Monte Carlo (PIGSMC) simulations in the Bose case. By varying the density and the coupling strength for the Lennard-Jones potential, we cover the whole range of dilute, weakly interacting gases up to the dense, strongly interacting case of liquid ³He and ⁴He. Below about 20 percent helium equilibrium density, the simplest version of the (F)HNC-EL theory is accurate within better than 1 percent.