Dense QCD: Overhauser or BCS pairing? art. no. 034015

We discuss the Overhauser effect (particle-hole pairing) versus the BCS eff ect (particle-particle or hole-hole pairing) in QCD at large quark density. In weak coupling and to leading logarithm accuracy, the pairing energies c an be estimated exactly. For a small number of colors, the BCS effect overt akes 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 reminiscen t of dense Skyrmions. The Overhauser effect is dominant in QCD in 1+1 dimen sions, although susceptible to quantum effects. It is sensitive to temperat ure in all dimensions.