On the Transport Properties of a Quark-Hadron Coulomb Lattice in the Cores of Neutron Stars

TL;DR

This paper investigates how rare phase blobs in the mixed quark-hadron core of neutron stars affect their thermal and transport properties, revealing negligible impact on specific heat but significant influence on neutrino emissivity at low temperatures.

Contribution

It provides the first detailed calculation of the transport and thermal properties of quark-hadron mixed phases considering rare phase blobs in neutron star cores.

Findings

Rare phase blobs negligibly affect specific heat.

Electron-blob Bremsstrahlung neutrino emissivity is significant below 10^8 K.

Results differ from standard neutron star matter properties.

Abstract

Already more that 40 years ago, it has been suggested that because of the enormous mass densities in the cores of neutron stars, the hadrons in the centers of neutron stars may undergo a phase transition to deconfined quark matter. In this picture, neutron stars could contain cores made of pure (up, down, strange) quark matter which are surrounded by a mixed phase of quarks and hadrons. More than that, because of the competition between the Coulomb and the surface energies associated with the positively charged regions of nuclear matter and negatively charged regions of quark matter, the mixed phase may develop geometrical structures, similarly to what is expected of the sub-nuclear liquid-gas phase transition. In this paper we restrict ourselves to considering the formation of rare phase blobs in the mixed quark-hadron phase. The influence of rare phase blobs on the thermal and transport properties of neutron star matter is investigated. The total specific heat, $c_V$, thermal conductivity, $\kappa$, and electron-blob Bremsstrahlung neutrino emissivities, $\epsilon_{\nu,\text{BR}}$, of quark-hybrid matter are computed and the results are compared with the associated thermal and transport properties of standard neutron star matter. Our results show that the contribution of rare phase blobs to the specific heat is negligibly small. This is different for the neutrino emissivity from electron-blob Bremsstrahlung scattering, which turns out to be of the same order of magnitude as the total contributions from other Bremsstrahlung processes for temperatures below about $10^8$ K.