Liquid-gas coexistence vs. energy minimization with respect to the density profile in the inhomogeneous inner crust of neutron stars

TL;DR

This paper compares phase-coexistence and energy minimization methods for modeling the inhomogeneous inner crust of neutron stars, highlighting differences in accuracy for proton fractions and surface properties.

Contribution

It introduces a comparative analysis of two modeling approaches for neutron star crusts, emphasizing the importance of energy minimization for detailed properties.

Findings

Phase-coexistence model reasonably describes cluster and gas densities.

Precision of phase-coexistence is insufficient for accurate proton fractions at low densities.

Energy minimization provides detailed surface tension and neutron skin information.

Abstract

We compare two approaches to describe the inner crust of neutron stars: on the one hand, the simple coexistence of a liquid (clusters) and a gas phase, and on the other hand, the energy minimization with respect to the density profile, including Coulomb and surface effects. We find that the phase-coexistence model gives a reasonable description of the densities in the clusters and in the gas, but the precision is not high enough to obtain the correct proton fraction at low baryon densities. We also discuss the surface tension and neutron skin obtained within the energy minimization.