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

With the standard techniques to deal with the sign problem in a diffusion M onte 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 H e-3 at zero temperature. Our analysis points to the necessity of including optimized backflow correlations to quantitatively improve the FN-DMC result s. The theoretical equation of state so obtained fits the experimental data for the energy, the pressure and the sound velocity. The upper bounds prov ided 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 r espect to the characteristic size of the statistical error.