Symmetry energy of warm nuclear systems

TL;DR

This paper investigates how the symmetry energy and free energy coefficients of nuclear matter and finite nuclei change with temperature, revealing weaker dependence near saturation and significant variation in finite nuclei.

Contribution

It introduces a global liquid-drop-inspired fit to resolve discrepancies in symmetry energy definitions and models finite nuclei with a finite-temperature-Thomas-Fermi approach including surface phonon effects.

Findings

Symmetry energy coefficients vary less with temperature near saturation density.

Finite nuclei show substantial temperature dependence in symmetry energy coefficients.

Different definitions of symmetry energy in literature lead to varying values.

Abstract

The temperature dependence of the symmetry energy and symmetry free energy coefficients of infinite nuclear matter and of finite nuclei is investigated. For infinite matter, both these coefficients are found to have a weaker dependence on temperature at densities close to saturation; at low but homogeneous densities, the temperature dependence becomes stronger. For finite systems, different definitions of symmetry energy coefficients are encountered in the literature yielding different values. A resolution to this problem is suggested from a global liquid-drop-inspired fit of the energies and free energies of a host of nuclei covering the entire periodic table. The hot nucleus is modeled in a subtracted finite-temperature-Thomas-Fermi framework, with dynamical surface phonon coupling to nucleonic motion plugged in. Contrary to infinite nuclear matter, a substantial change in the symmetry energy coefficients is observed for finite nuclei with temperature.