Crystalline color superconductors

TL;DR

This paper reviews the properties and astrophysical implications of crystalline color superconductors, a type of inhomogeneous quark matter phase potentially present in the cores of compact stars.

Contribution

It provides a comprehensive overview of inhomogeneous color superconducting phases, especially crystalline ones, and discusses their potential observational signatures in astrophysics.

Findings

Crystalline color superconductors may exist in dense quark matter inside compact stars.

Inhomogeneous phases could influence star cooling and gravitational wave signals.

The review highlights the conditions favoring these phases over standard BCS pairing.

Abstract

Inhomogeneous superconductors and inhomogeneous superfluids appear in a variety of contexts including quark matter at extreme densities, fermionic systems of cold atoms, type-II cuprates, and organic superconductors. In the present review the focus is on properties of quark matter at high baryonic density, which may exist in the interior of compact stars. The conditions realized in these stellar objects tend to disfavor standard symmetric BCS pairing and may favor an inhomogeneous color superconducting phase. The properties of inhomogeneous color superconductors are discussed in detail and in particular of crystalline color superconductors. The possible astrophysical signatures associated with the presence of crystalline color superconducting phases within the core of compact stars are also reviewed.