Unified nuclear matter EOSs constrained by the in-medium balance in density-dependent covariant density functionals

TL;DR

This paper develops a self-consistent numerical method to study the equation of state and microscopic structures of nuclear matter across a wide density range, with implications for neutron star properties.

Contribution

It introduces a new numerical recipe within the Thomas-Fermi approximation for nuclear matter, incorporating charge screening and diverse nuclear structures, constrained by covariant density functionals.

Findings

Different EOSs predicted by DD-LZ1 and DD-ME2 functionals.

Variety of nuclear matter structures observed, including droplets, rods, slabs, tubes, bubbles, and uniform matter.

Predicted neutron star mass-radius relations vary with the functional used.

Abstract

Considering the effects of charge screening, we propose a new numerical recipe within the framework of Thomas-Fermi approximation, where the properties of nuclear matter throughout a vast density range can be obtained self-consistently. Assuming spherical and cylindrical approximations for the Wigner-Seitz cell, typical nuclear matter structures (droplet, rod, slab, tube, bubble, and uniform) are observed. We then investigate the EOSs and microscopic structures of nuclear matter with both fixed proton fractions and $\beta$-equilibration, where two covariant density functionals DD-LZ1 and DD-ME2 are adopted. Despite the smaller slope $L$ of symmetry energy obtained with the functional DD-LZ1, the curvature parameter $K_\mathrm{sym}$ is much larger than that of DD-ME2, which is attributed to the peculiar density-dependent behavior of meson-nucleon couplings guided by the restoration of pseudo-spin symmetry around the Fermi levels in finite nuclei. Consequently, different mass-radius relations of neutron stars are predicted by the two functionals. Different microscopic structures of nonuniform nuclear matter are obtained as well, which are expected to affect various physical processes in neutron star properties and evolutions.