Superfluidity and entrainment in neutron-star crusts

TL;DR

This paper investigates neutron superfluidity and entrainment effects in neutron-star crusts, revealing significant entrainment of neutrons by the crust which may impact astrophysical observations.

Contribution

It provides a systematic band theory analysis of superfluidity and entrainment across all regions of the neutron star's inner crust, highlighting the extent of neutron entrainment.

Findings

Large fraction of free neutrons are entrained by the crust

Entrainment effects are significant in intermediate crust layers

Results suggest revising interpretations of astrophysical phenomena

Abstract

Despite the absence of viscous drag, the neutron superfluid permeating the inner crust of a neutron star can still be strongly coupled to nuclei due to non-dissipative entrainment effects. Neutron superfluidity and entrainment have been systematically studied in all regions of the inner crust of a cold non-accreting neutron star in the framework of the band theory of solids. It is shown that in the intermediate layers of the inner crust a large fraction of "free" neutrons are actually entrained by the crust. The results suggest that a revision of the interpretation of many observable astrophysical phenomena might be necessary.