Equation of state of isospin-asymmetric nuclear matter in relativistic mean-field models with chiral limits

TL;DR

This paper develops new relativistic mean-field models incorporating chiral symmetry restoration effects, which accurately describe nuclear matter and neutron star properties consistent with experimental and observational data.

Contribution

The authors constructed novel RMF Lagrangians with chiral limits, fitting them to heavy-ion collision data and isospin diffusion results, providing a unified description of nuclear matter and neutron stars.

Findings

Equation of state is soft at intermediate densities and stiff at high densities.

Predicted radius of a 1.4 solar mass neutron star is between 11.9 and 13.1 km.

Maximum neutron star mass is around 2.0 solar masses.

Abstract

Using in-medium hadron properties according to the Brown-Rho scaling due to the chiral symmetry restoration at high densities and considering naturalness of the coupling constants, we have newly constructed several relativistic mean-field Lagrangians with chiral limits. The model parameters are adjusted such that the symmetric part of the resulting equation of state at supra-normal densities is consistent with that required by the collective flow data from high energy heavy-ion reactions, while the resulting density dependence of the symmetry energy at sub-saturation densities agrees with that extracted from the recent isospin diffusion data from intermediate energy heavy-ion reactions. The resulting equations of state have the special feature of being soft at intermediate densities but stiff at high densities naturally. With these constrained equations of state, it is found that the radius of a 1.4$M_\odot$ canonical neutron star is in the range of 11.9 km$\leq$R$\leq$13.1 km, and the maximum neutron star mass is around 2.0$M_\odot$ close to the recent observations.