Quantum Monte Carlo calculation of the equation of state of neutron matter

We calculate the equation of state of neutron matter at zero temperature by means of the auxiliary field diffusion Monte Carlo method (AFDMC) combined with a fixed-phase approximation. The calculation of the energy is carried out by simulating up to 114 neutrons in a periodic box. Special attention was made to reduce finite size effects at the energy evaluation by adding to the interaction the effect due to the truncation of the simulation box, and by performing several simulations using different number of neutrons. The finite size effects due to the kinetic energy were also checked by employing the twist--averaged boundary conditions. We considered a realistic nuclear Hamiltonian containing modern two-- and three--body interactions of the Argonne and Urbana family. The equation of state can be used to compare and to calibrate other many-body calculations and to predict properties of neutron stars.