Light dark matter scattering in outer neutron star crusts

TL;DR

This paper investigates how light dark matter particles interact with the outer crust of neutron stars, affecting phonon excitation and thermal conductivity, which could influence heat conduction in magnetized neutron stars.

Contribution

First calculation of phonon excitation rates due to light dark matter scattering in neutron star crusts, revealing significant effects on thermal properties.

Findings

LDM modifies phonon populations compared to thermal expectations.

LDM can significantly enhance ion-ion thermal conductivity at high densities.

Enhanced conductivity may reduce anisotropic heat conduction in magnetized neutron stars.

Abstract

We calculate for the first time the phonon excitation rate in the outer crust of a neutron star due to scattering from light dark matter (LDM) particles gravitationally boosted into the star. We consider dark matter particles in the sub-GeV mass range scattering off a periodic array of nuclei through an effective scalar-vector interaction with nucleons. We find that LDM effects cause a modification of the net number of phonons in the lattice as compared to the standard thermal result. In addition, we estimate the contribution of LDM to the ion-ion thermal conductivity in the outer crust and find that it can be significantly enhanced at large densities. Our results imply that for magnetized neutron stars the LDM-enhanced global conductivity in the outer crust will tend to reduce the anisotropic heat conduction between perpendicular and parallel directions to the magnetic field.