The symmetry energy $\gamma$ parameter of relativistic mean-field models

TL;DR

This study revisits relativistic mean-field models to analyze the symmetry energy parameter gamma, revealing linear correlations with symmetry energy, its slope, and neutron star radii, and identifying specific parametrizations compatible with astrophysical constraints.

Contribution

It provides a detailed analysis of the gamma parameter in relativistic mean-field models, establishing new linear correlations and identifying compatible parametrizations with astrophysical data.

Findings

Linear correlation between gamma and symmetry energy ($\\mathcal{S}_0$).

Clear linear relationship between gamma and the slope ($L_0$).

Identification of parametrizations compatible with neutron star constraints.

Abstract

The relativistic mean-field models tested in previous works against nuclear matter experimental values, critical parameters and macroscopic stellar properties are revisited and used in the evaluation of the symmetry energy $\gamma$ parameter obtained in three different ways. We have checked that independent of the choice made to calculate the $\gamma$ values, a trend of linear correlation is observed between $\gamma$ and the symmetry energy ($\mathcal{S}_0$) and a more clear linear relationship is established between $\gamma$ and the slope of the symmetry energy ($L_0$). These results directly contribute to the arising of other linear correlations between $\gamma$ and the neutron star radii of $R_{1.0}$ and $R_{1.4}$, in agreement with recent findings. Finally, we have found that short-range correlations induce two specific parametrizations, namely, IU-FSU and DD-ME$\delta$, simultaneouslycompatible with the neutron star mass constraint of $1.93 < M_{max}/M_\odot < 2.05$ and with the overlap band for the $L_0\times\mathcal{S}_0$ region, to present $\gamma$ in the range of $\gamma=0.25\pm0.05$.