Properties of pure neutron matter at low and high densities

We report a new microscopic equation of state (EoS) of pure neutron matter (PNM) at zero temperature using the recent realistic two-body interaction derived in the framework of chiral perturbation theory (ChPT). The EoS is derived using the Brueckner-Bethe-Goldstone quantum many-body theory in the Brueckner-Hartree-Fock approach. We have calculated the EoS of PNM at low and high densities using LO, NLO, N2LO, N3LO, N4LO potentials at three different values of the momentum-space cut-off Lambda = 450, 500 and 550 MeV. It is found that the EoS is not much affected by the cut-off variations at low densities. Also the binding energy of PNM has been computed within the framework of the Brueckner-Hartree-Fock (BHF) approach plus two-body density-dependent Skyrme potential which is equivalent to three-body forces. The effect of the two-body density-dependent Skyrme potential is to produce a stiffer EoS. This is actually needed to improve the saturation point of symmetric nuclear matter obtained using the two-body NN interaction. The results of several microscopic approaches are compared. It is found that the EoS is sensitive to the momentum-space cut-off Lambda. Also the partial wave contributions to potential energy at the empirical saturation density rho =0.16 fm-3 for different potentials are listed from 1S0 to 3F3 states. It is found that all contributions are nearly cut-off independent except the ones from 3P1, 3P2,3H4 and 3F4 states, which are increasing with the cut-off Lambda. Actually, the size of these contributions is strongly dependent on the central and tensor components in the NN potential. The larger cut-off Lambda corresponds to harder interactions and gives more repulsive contribution to the NN potential at short distance. It leads to smaller binding energy.

Automated summary

In this study, a new microscopic equation of state (EoS) for pure neutron matter (PNM) at zero temperature was derived using realistic two-body interactions obtained from chiral perturbation theory. The EoS was found to be sensitive to the momentum-space cut-off Lambda, and the inclusion of two-body density-dependent Skyrme potential resulted in a stiffer EoS. Comparisons with other microscopic approaches were made, showing the importance of central and tensor components in the NN potential for determining the binding energy.