Nuclear symmetry energy and the role of three-body forces

TL;DR

This study investigates the density dependence of nuclear symmetry energy and its partial wave decomposition using a revised three-body force model within the LOCV framework, successfully reproducing key nuclear matter parameters and neutron star properties.

Contribution

Introduces a new isospin-dependent parametrization of three-body forces that improves saturation point predictions in the LOCV method.

Findings

Reproduces semi-empirical nuclear matter parameters.

Predicts neutron star maximum mass above 2 solar masses.

Shows proton fraction in neutron stars depends on three-body force parametrization.

Abstract

Density dependence of nuclear symmetry energy as well as its partial wave decomposition is studied within the framework of lowest-order constrained variational (LOCV) method using AV18 two-body interaction supplemented by UIX three-body force. The main focus of the present work is to introduce a revised version of three-body force which is based on an isospin-dependent parametrization of coefficients in the UIX force, in order to overcome the inability to produce correct saturation-point parameters} in the framework of LOCV method. We find that employing the new model of {\ph three-body force} in the LOCV formalism leads to successfully reproducing the semi-empirical parameters of cold nuclear matter, including} $E_{sym}(\rho_0)$, $L$, and $K_{sym}$. All our models of three-body force combined with AV18 two-body force give maximum neutron star mass higher than $2\;M_\odot$. The fraction of protons in the nucleon cores of neutron stars strongly depends on the three-body force parametrization.