Systematic analysis of inner crust composition using the extended Thomas-Fermi approximation with pairing correlations

TL;DR

This study systematically analyzes the inner crust composition of neutron stars using advanced nuclear models, revealing correlations between the equation of state and crust properties, with implications for understanding neutron star structure.

Contribution

It introduces a comprehensive approach combining extended Thomas-Fermi, shell corrections, and pairing to evaluate crust composition across multiple Skyrme functionals.

Findings

Inner crust proton number correlates with low-density PNM EoS.

Crust pressure is linked to the PNM EoS at lower densities.

Functional choice significantly affects predicted crust composition.

Abstract

We perform a systematic investigation of the chemical composition of the inner crust of a neutron star, using the extended Thomas-Fermi approximation, the Strutinsky integral correction for shell effects, and the BCS approximation for pairing. Fifteen Skyrme functionals were selected, which cover the range of values of important bulk properties of infinite nuclear matter, while also having pure neutron matter (PNM) equation of states (EoS) with varying degrees of stiffness. We find that a functional's low-density PNM EoS is correlated with the number of protons found in the inner crust's nuclear clusters and, in the lower-density region of the inner crust, with the pressure.