A new approach for the equation of state of pure neutron matter using the quantum second virial coefficient with the Reid-93 soft-core potential

Abstract

In this work, a new approach is presented for determining the equation of state for pure neutron matter. This is valid in the temperature- and density-regime where the system behaves like a nonideal gas. Further, the calculations involved are confined to the nonrelativistic and low-energy ([Formula: see text] 150 MeV) regime. The approach is based on evaluating the quantum second virial coefficient [Formula: see text] of the system, where the input potential is the Reid-93 soft-core potential for [Formula: see text], together with the one-pion-exchange potential (OPEP) for higher [Formula: see text]. The many-body phase shifts are determined within the framework of a generalized scattering theory, taken here as the Galitskii–Migdal–Feynman formalism. The integral equations involved are solved using a highly-accurate matrix-inversion method. These medium phase shifts are then inserted in the Beth–Uhlenbeck formula to determine [Formula: see text]. Once this coefficient has been calculated, other thermophysical properties of the system can be readily computed according to standard expressions. Specifically, these properties include the equation of state (pressure–temperature–density relations), Helmholtz (free) energy, entropy, mean internal energy, specific heat capacity and chemical potential. Our results are compared, whenever possible, to those of previous calculations. The agreement is, on the whole, fair considering that the available calculations vary considerably among themselves.