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 colorsuperconducting 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 crosssection 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 in to 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 10 10 years.

Exploring phases of dense QCD with compact stars

“…The blue color is either unpaired or undergoes single-flavor and color pairing with very small gaps of the order of keV [7]. In addition to the bulk fermions, the 2SC phase can contain color-magnetic flux tubes which will carry partially the magnetic field through the color superconductor [44]. The flux tubes can effectively scatter bulk fermions and, therefore, contribute to the transport and relaxation in a certain parameter range, which we will discuss below.…”

Rotating hybrid compact stars

“…If the phase of interest is a superfluid, as is the case with the CFL phase, the onset of superfluidity doubles the dynamical degrees of freedom of the fluid and induces a differential rotation between the normal component, which is coupled to the star on short dynamical timescales and the superfluid component, which couples to the rest of the star via mutual friction (Mannarelli et al 2008). In the case of the 2SC phase, color magnetism of this phase requires generation of color magnetic flux tubes in quark matter (Alford & Sedrakian 2010). This may alter the magnetic properties of the stars and their spin-down under electromagnetic radiation.…”

Cold quark matter in astrophysics of compact stars

“…[22]. Our discussion will be focused on the formation and dynamics of flux tubes in the two-flavor color superconducting (2SC) phase.…”

“…The scattering of electrons and blue quarks of the flux tubes in the 2SC cores of compact stars contributes to the transport coefficients of matter and acts as a dissipative force on the flux tubes. The relaxation time for incident light fermion on a flux tube is given by [22] τ…”

“…Other contributions to the magnetic field from outside of the 2SC core have been neglected. Substituting the flux tension we obtain [22] f b ≈ 1 3π…”