Gap-bridging enhancement of modified Urca processes in nuclear matter

TL;DR

This paper demonstrates that density oscillations can significantly enhance neutrino emission in neutron-star matter by overcoming the suppression caused by nucleon pairing gaps, specifically in modified Urca processes with neutron pairing.

Contribution

It refines previous models by showing that gap bridging effectively counteracts Boltzmann suppression in realistic modified Urca processes with neutron pairing.

Findings

Density oscillations can overcome pairing gap suppression.

Neutrino emissivity is significantly enhanced by gap bridging.

Results are applicable to neutron-star cooling models.

Abstract

In nuclear matter at neutron-star densities and temperatures, Cooper pairing leads to the formation of a gap in the nucleon excitation spectra resulting in exponentially strong Boltzmann suppression of many transport coefficients. Previous calculations have shown evidence that density oscillations of sufficiently large amplitude can overcome this suppression for flavor-changing $\beta$ processes, via the mechanism of "gap bridging". We address the simplifications made in that initial work, and show that gap bridging can counteract Boltzmann suppression of neutrino emissivity for the realistic case of modified Urca processes in matter with $^3P_2$ neutron pairing.