Quantum Monte Carlo Lattice Simulation of Thermal Properties of Low-Density Neutron Matter*

Thermal properties of low-density neutron matter are investigated by nuclear many-body simulation on three-dimensional cubic lattice. Determinantal quantum Monte Carlo calculations are carried out for the Hamiltonian with a coupling constant of the neutron-neutron interaction determined from effective field theory. Method of finite-size scaling is applied to extract thermodynamical information. Phase diagram shows that low-density neutron matter undergoes a phase transition from a superfluid state to normal, as the temperature or the density increases. The results are also compared with the existing mean-field and related calculations.