Color-magnetic flux tubes in quark matter cores of neutron stars

Abstract

We argue that if color-superconducting quark matter exists in the core of a neutron star, it may contain a high density of flux tubes, carrying flux that is mostly color magnetic, with a small admixture of ordinary magnetic flux. We focus on the two-flavor color-superconducting (‘2SC’) phase, and assume that the flux tubes are energetically stable, although this has not yet been demonstrated. The density of flux tubes depends on the nature of the transition to the color-superconducting phase, and could be within an order of magnitude of the density of magnetic flux tubes that would be found if the core were superconducting nuclear matter. We calculate the cross-section for Aharonov–Bohm scattering of gapless fermions off the flux tubes, and the associated collision time and frictional force on a moving flux tube. We discuss the other forces on the flux tube, and find that if we take into account only the forces that arise within the 2SC core region, then the timescale for expulsion of the color flux tubes from the 2SC core is of order 1010 years.