MOMENTUM DISTRIBUTION OF LIQUID-HELIUM

We have obtained the one-body density matrix and the momentum distribu tion of liquid lie at T = 0 from Diffusion Monte Carlo simulations, us ing trial functions optimized via the Euler Monte Carlo (EMC) method. For He-4 we find a condensate fraction smaller than in previous calcul ations. For He-3, which we have studied within the fixed-node approxim ation, we analyze the momentum distribution around the Fermi surface. We also show that an approximate factorization of the one-body density matrix rho(r) similar or equal to rho(u)(r)rho(B)(r) holds, with rho( u)(r) and rho(B)(r) respectively the density matrix for the ideal (unc orrelated) Fermi gas and the density matrix of a mass 3 Bose system.