Eur. Phys. J. A (2016) 52: 57
https://doi.org/10.1140/epja/i2016-16057-6

Review

Inhomogeneous chiral symmetry breaking in dense neutron-star matter

Theoriezentrum, Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany

^* e-mail: Michael.Buballa@physik.tu-darmstadt.de

Received: 18 August 2015
Revised: 30 November 2015
Accepted: 14 December 2015
Published online: 18 March 2016

Abstract

An increasing number of model results suggests that chiral symmetry is broken inhomogeneously in a certain window at intermediate densities in the QCD phase diagram. This could have significant effects on the properties of compact stars, possibly leading to new astrophysical signatures. In this contribution we discuss this idea by reviewing recent results on inhomogeneous chiral symmetry breaking under an astrophysics-oriented perspective. After introducing two commonly studied spatial modulations of the chiral condensate, the chiral density wave and the real kink crystal, we focus on their properties and their effect on the equation of state of quark matter. We also describe how these crystalline phases are affected by different elements which are required for a realistic description of a compact star, such as charge neutrality, the presence of magnetic fields, vector interactions and the interplay with color superconductivity. Finally, we discuss possible signatures of inhomogeneous chiral symmetry breaking in the core of compact stars, considering the cases of mass-radius relations and neutrino emissivity explicitly.