Dense QCD : Overhauser or BCS Pairing ?

TL;DR

This paper compares Overhauser and BCS pairing mechanisms in dense QCD, analyzing their dominance depending on coupling strength and number of colors, with implications for the phase structure of quark matter.

Contribution

It provides a detailed comparison of particle-hole and particle-particle pairing effects in QCD at high density, including their dependence on coupling strength and color number.

Findings

BCS effect dominates for small number of colors at weak coupling

Overhauser effect may dominate at strong coupling regardless of color number

QCD may form an insulating phase due to Overhauser pairing at high density

Abstract

We discuss the Overhauser effect (particle-hole pairing) versus the BCS effect (particle-particle or hole-hole pairing) in QCD at large quark density. In weak coupling and to leading logarithm accuracy, the pairing energies can be estimated exactly. For a small number of colors, the BCS effect overtakes the Overhauser effect, while for a large number of colors the opposite takes place, in agreement with a recent renormalization group argument. In strong coupling with large pairing energies, the Overhauser effect may be dominant for any number of colors, suggesting that QCD may crystallize into an insulator at a few times nuclear matter density, a situation reminiscent of dense Skyrmions. The Overhauser effect is dominant in QCD in 1+1 dimensions, although susceptible to quantum effects. It is sensitive to temperature in all dimensions.