The rigidity of three flavor quark matter

TL;DR

This paper investigates the properties of crystalline color superconducting quark matter, revealing it to be an extremely rigid superfluid phase that could influence neutron star phenomena like pulsar glitches.

Contribution

It derives the effective action for phonon fluctuations and calculates the shear modulus, showing this phase's exceptional rigidity compared to neutron star crusts.

Findings

Shear modulus is 20 to 1000 times larger than neutron star crusts.

Crystalline color superconducting phase is both superfluid and highly rigid.

Potential implications for neutron star phenomenology, such as pulsar glitches.

Abstract

Cold three flavor quark matter at large (but not asymptotically large) densities may exist in a crystalline color superconducting phase. These phases are characterized by a gap parameter $\Delta$ that varies periodically in space, forming a crystal structure. A Ginzburg-Landau expansion in $\Delta$ shows that two crystal structures based on cubic symmetry are particularly favorable, and may be the ground state of matter at densities present in neutron star cores. We derive the effective action for the phonon fields that describe space- and time-dependent fluctuations of the crystal structure formed by $\Delta$, and obtain the shear modulus from the coefficients of the spatial derivative terms. Within a Ginzburg-Landau approximation, we find shear moduli which are 20 to 1000 times larger than those of neutron star crusts. This phase of matter is thus more rigid than any known material in the universe, but at the same time the crystalline color superconducting phase is also superfluid. These properties raise the possibility that the presence of this phase within neutron stars may have distinct implications for their phenomenology. For example, (some) pulsar glitches may originate in crystalline superconducting neutron star cores.