Pure Neutron Matter Constraints and Nuclear Symmetry Energy

TL;DR

This review discusses how recent ab initio constraints on pure neutron matter inform the optimization of nuclear energy-density functionals, leading to consistent symmetry energy parameters and insights into neutron star properties.

Contribution

The paper introduces a method to optimize isovector parameters of nuclear EDFs using ab initio PNM constraints, improving the consistency of symmetry energy predictions.

Findings

Optimized EDFs yield consistent symmetry energy $J$ and slope $L$ within tight uncertainties.

Model dependence appears in the curvature $K_{sym}$, high-density symmetry energy, and neutron star radii.

Abstract

In this review, we will discuss the results of our recent work to study the general optimization of the pure isovector parameters of the popular relativistic mean-field (RMF) and Skyrme-Hartree-Fock (SHF) nuclear energy-density functionals (EDFs), using constraints on the pure neutron matter (PNM) equation of state (EoS) from recent {\sl ab initio} calculations. By using RMF and SHF parameterizations that give equivalent predictions for ground-state properties of doubly magic nuclei and properties of symmetric nuclear matter (SNM) and PNM, we found that such optimization leads to broadly consistent symmetry energy $J$ and its slope parameter $L$ at saturation density within a tight range of $\sigma(J) < 2$ MeV and $\sigma(L) < 6$ MeV. We demonstrate that a clear model dependence shows up (a) in the curvature parameter of the symmetry energy $K_{\rm sym}$, (b) the symmetry energy at supra-saturation densities, and (c) the radius of neutron stars.