Nuclear potentials relevant to the symmetry energy in chiral models

TL;DR

This paper compares different chiral models to understand nuclear potentials and symmetry energy, highlighting how chiral symmetry restoration affects these properties at high densities.

Contribution

It evaluates the impact of chiral limits in various models on nuclear matter properties and symmetry energy, providing insights into high-density behavior.

Findings

Scalar fields influence symmetry potentials and energies across densities.

Chiral restoration causes a rise in kinetic symmetry energy.

Chiral limit softens symmetry potential and energy at high densities.

Abstract

We employ the extended Nambu-Jona-Lasinio, linear-$\sigma$ models, and the density-dependent model with chiral limits to work out the mean fields and relevant properties of nuclear matter. To have the constraint from the data, we reexamine the Dirac optical potentials and symmetry potential based on the relativistic impulse approximation (RIA). Unlike the extended NJL and the density-dependent models with the chiral limit in terms of the vanishing scalar density, the extended linear-$\sigma$ model with a sluggish changing scalar field loses the chiral limit at the high density end. The various scalar fields can characterize the different Schr\"odinger-equivalent potentials and kinetic symmetry energy in the whole density region and the symmetry potential in the intermediate density region. The drop of the scalar field due to the chiral restoration results in a clear rise of the kinetic symmetry energy. The chiral limit in the models gives rise to the softening of the symmetry potential and thereof the symmetry energy at high densities.