Topological confinement of vortices in two-flavor dense QCD

TL;DR

This paper introduces a new confinement mechanism for vortices in two-flavor dense QCD, distinguishing confined and deconfined phases based on color neutrality of Aharonov-Bohm phases, and describes the structure of vortex bound states.

Contribution

It identifies a novel confinement criterion in dense QCD involving AB phases and characterizes the structure of vortex bound states in different phases.

Findings

Confined phase features baryonic and mesonic vortex bound states.

Deconfined phase hosts non-Abelian Alice strings with fractional flux.

Color neutrality of AB phases determines vortex confinement status.

Abstract

We find a novel confinement mechanism in the two-flavor dense quark matter proposed recently, that consists of the 2SC condensates and the $P$-wave diquark condensates of $d$-quarks. This quark matter exhibiting color superconductivity as well as superfluidity is classified into two phases; confined and deconfined phases of vortices. We establish that the criterion of the confinement is color neutrality of Aharonov-Bohm (AB) phases: vortices exhibiting color non-singlet AB phases are confined by the so-called AB defects to form color-singlet bound states. In the deconfined phase, the most stable vortices are non-Abelian Alice strings, which are superfluid vortices with fractional circulation and non-Abelian color magnetic fluxes therein, exhibiting color non-singlet AB phases. On the other hand, in the confined phase, these non-Abelian vortices are confined to either a baryonic or mesonic bound state in which constituent vortices are connected by AB defects. The baryonic bound state consists of three non-Abelian Alice strings with different color magnetic fluxes with the total flux canceled out connected by a domain wall junction, while the mesonic bound state consists of two non-Abelian Alice strings with the same color magnetic fluxes connected by a single domain wall. Interestingly, the latter contains a color magnetic flux in its core, but this can exist because of color neutrality of its AB phase.