1205.0857 (F. J. Fattoyev et al.)

Pure Neutron Matter Constraints on the Relativistic Mean-Field and Skyrme-Hartree-Fock Models    [PDF]

F. J. Fattoyev, W. G. Newton, Jun Xu, Bao-An Li

Using constraints on the pure neutron matter (PNM) equation of state (EoS) from recent \emph{ab initio} calculations, we present a general optimization of the pure isovector parameters of the popular relativistic mean-field (RMF) and Skyrme-Hartree-Fock (SHF) nuclear energy-density functionals (EDFs) while maintaining the broad quality of the predictions for binding energies and charge radii of nuclei. Such optimization leads to broadly consistent and tight predictions of the symmetry energy $J$ and its slope parameter $L$ at saturation density with associated joint 1$\sigma$ confidence ellipses in the $J-L$ plane. We demonstrate that given this optimization, the resulting neutron skin thicknesses are consistent with the experimental data so far, but clear model dependence shows up in (a) the slope of the correlation between $J$ and $L$ from the confidence ellipse, (b) the curvature parameter of the symmetry energy $K_{\rm sym}$, (c) the symmetry energy at supra-saturation densities, and (d) the neutron star radius. Notably, the RMF and SHF models are shown to be only marginally consistent at best with constraints on the isospin-dependent part of the incompressibility of neutron-rich nuclear matter $K_{\tau}$, and that the model dependence can lead to about 1 km difference of the neutron star radius given the same values of $J$, $L$ and symmetric nuclear matter (SNM) saturation properties.

View original: http://arxiv.org/abs/1205.0857