Landau parameters and entrainment matrix of cold stellar matter: effect of the symmetry energy and strong magnetic fields

TL;DR

This paper investigates how the symmetry energy and strong magnetic fields influence nuclear matter properties relevant to neutron stars, revealing significant dispersions at high densities and minor magnetic effects except near the crust-core transition.

Contribution

It provides a comprehensive analysis of the effects of symmetry energy and magnetic fields on nuclear matter properties using relativistic mean-field models, including detailed tables of EoS and parameters.

Findings

Large dispersion in properties at 2-3 times saturation density.

Proton Landau mass can be as low as one third of nucleon mass.

Magnetic field effects are small except near crust-core transition.

Abstract

Nuclear matter properties based on a relativistic approach suitable for the description of multi-component systems are calculated. We use a set of nuclear relativistic mean-field models that satisfy acceptable nuclear matter properties and neutron star observations. The effects of the density dependence of the symmetry energy and of the Landau quantization due to the presence of a strong external magnetic field are discussed. Properties such as the proton fraction, the Landau mass, Landau parameters and entrainment matrix, the adiabatic index and speed of sound are calculated for cold $\beta$-equilibrium matter. A large dispersion on the calculated properties is obtained at two to three times saturation density $\rho_0 $. The proton Landau mass can be as low as one third of the vacuum nucleon mass at 2-3$~\rho_0 $. Similar effects are obtained for the Landau parameters, in particular, the ones involving protons, where the relative dispersion of $F^0_{pp}$ and $F^1_{pp}$ is as high as 30\% to 50\% at 2-3$~\rho_0 $. These parameters are particularly sensitive to the symmetry energy. The effect of the magnetic field on the nuclear properties is small for fields as high as 10$^{18}$G except for a small range of densities just above the crust-core transition. Tables with the EoS, and the parameters, are provided in the Supplementary Material section.