New color-magnetic defects in dense quark matter

TL;DR

This paper investigates novel color-magnetic flux tubes and domain walls in dense quark matter using a Ginzburg-Landau model, revealing configurations that could influence neutron star properties and gravitational wave signals.

Contribution

It introduces new energetically favored flux tube solutions and magnetic domain walls in color-superconducting quark matter, expanding understanding of magnetic defects in dense QCD phases.

Findings

Identifies a new preferred flux tube configuration in CFL matter.

Discovers magnetic domain walls in the 2SC phase.

Suggests these defects could cause observable gravitational waves.

Abstract

Color-flavor locked (CFL) quark matter expels color-magnetic fields due to the Meissner effect. One of these fields carries an admixture of the ordinary abelian magnetic field and therefore flux tubes may form if CFL matter is exposed to a magnetic field, possibly in the interior of neutron stars or in quark stars. We employ a Ginzburg-Landau approach for three massless quark flavors, which takes into account the multi-component nature of color superconductivity. Based on the weak-coupling expressions for the Ginzburg-Landau parameters, we identify the regime where CFL is a type-II color superconductor and compute the radial profiles of different color-magnetic flux tubes. Among the configurations without baryon circulation we find a new solution that is energetically preferred over the flux tubes previously discussed in the literature in the parameter regime relevant for compact stars. Within the same setup, we also find a new defect in the 2SC phase, namely magnetic domain walls, which emerge naturally from the previously studied flux tubes if a more general ansatz for the order parameter is used. Color-magnetic defects in the interior of compact stars allow for sustained deformations of the star, potentially strong enough to produce detectable gravitational waves.