Stability of superfluid vortices in dense quark matter

TL;DR

This study investigates the stability of superfluid vortices in dense quark matter's CFL phase, revealing they are likely unstable in realistic conditions, favoring semi-superfluid flux tubes in neutron star cores.

Contribution

The paper provides the first numerical analysis of vortex stability in the CFL phase, identifying parameter regions where vortices are metastable or unstable, including an analytical unstable mode for zero gauge coupling.

Findings

Superfluid vortices are generally unstable in realistic CFL quark matter.

Numerical calculations align with analytical unstable mode predictions.

Implication that neutron star cores likely contain semi-superfluid flux tubes.

Abstract

Superfluid vortices in the color-flavor-locked (CFL) phase of dense quark matter are known to be energetically disfavored relative to well-separated triplets of "semi-superfluid" color flux tubes. However, the short-range interaction (metastable versus unstable) has not been established. In this paper we perform numerical calculations using the effective theory of the condensate field, mapping the regions in the parameter space of coupling constants where the vortices are metastable versus unstable. For the case of zero gauge coupling we analytically identify a candidate for the unstable mode, and show that it agrees well with the results of the numerical calculations. We find that in the region of the parameter space that seems likely to correspond to real-world CFL quark matter the vortices are unstable, indicating that if such matter exists in neutron star cores it is very likely to contain semi-superfluid color flux tubes rather than superfluid vortices.