New perspectives in the application of the diffusion Monte Carlo method to the study of liquid 3He

With the standard techniques to deal with the sign problem in a diffusion Monte Carlo (DMC) calculation, i.e., fixed node (FN) and released node (RN), we have re-explored the application of DMC to the study of normal liquid He-3 at zero temperature. Our analysis points to the necessity of including optimized backflow correlations to quantitatively improve the FN-DMC results. The theoretical equation of state so obtained fits the experimental data for the energy, the pressure and the sound velocity. The upper bounds provided by the FN method are checked on the one hand by the application of RN, and on the other, by the inclusion of explicit three-body correlations in the backflow operator. Both calculations show negligible corrections with respect to the characteristic size of the statistical error.