Quark beta decay in an inhomogeneous chiral phase and cooling of hybrid stars

TL;DR

This paper explores how inhomogeneous chiral phases, specifically the dual-chiral-density-wave, influence neutrino emission and cooling in hybrid stars, revealing a potential mechanism for mass-dependent cooling differences.

Contribution

It introduces the impact of the DCDW phase on neutrino emissivity and star cooling, highlighting a novel inhomogeneous phase effect on astrophysical phenomena.

Findings

Neutrino emissivity is enhanced in the DCDW phase.

The DCDW phase can make the quark direct Urca process possible.

Cooling rates vary with the density region of the DCDW phase.

Abstract

We discuss the cooling of hybrid stars by considering the neutrino emission from quark matter. As a current topic the appearance of various inhomogeneous chiral phases have been studied near the chiral transition. Here we consider the dual-chiral-density-wave (DCDW) specified by the spatially modulated quark condensates. Since the DCDW state can be represented as a chirally rotated state from the normal quark matter, the quark weak-current is accordingly transformed to have an additional phase factor which modifies the energy-momentum conservation at the vertex, and makes the quark direct Urca process possible. The direct evaluation of the neutrino emissivity shows that it is proportional to and the magnitude is comparable with the quark or pion cooling. Since the DCDW phase develops only in the limited density region, this novel mechanism may give an interesting scenario about cooling of hybrid stars that lower-mass stars should be cooler than higher-mass ones.