Symmetry energy softening in nuclear matter with non-nucleonic constituents

TL;DR

This paper investigates how the nuclear symmetry energy softens at high densities due to the appearance of hyperons and quark matter, impacting the equation of state in dense nuclear environments.

Contribution

It introduces a detailed analysis of symmetry energy behavior with hyperons and quark phases within relativistic mean-field models, highlighting the softening effects at high densities.

Findings

Symmetry energy softens with hyperon inclusion, especially $ ext{Λ}$ hyperons.

In quark-hadron mixed phases, symmetry energy decreases with increasing quark volume fraction.

Softening of symmetry energy correlates with potential signals in heavy-ion collision experiments.

Abstract

We study the trend of the nuclear symmetry energy in relativistic mean-field models with appearance of the hyperon and quark degrees of freedom at high densities. On the pure hadron level, we focus on the role of $\Lambda$ hyperons in influencing the symmetry energy both at given fractions and at charge and chemical equilibriums. The softening of the nuclear symmetry energy is observed with the inclusion of the $\Lambda$ hyperons that suppresses the nucleon fraction. In the phase with the admixture of quarks and hadrons, the equation of state is established on the Gibbs conditions. With the increase of the quark volume fraction in denser and denser matter, the apparent nuclear symmetry energy decreases till to disappear. This softening would have associations with the observations which need detailed discriminations in dense matter with the admixture of new degrees of freedom created by heavy-ion collisions.