Color Superconductivity at Large N: A New Hope

Abstract

At zero density, the `t Hooft large N_c limit often provides some very useful qualitative insights into the non-perturbative physics of QCD. However, it is known that at high densities the `t Hooft large N_c world looks very different from the N_c=3 world, which is believed to be in a color superconducting phase at high densities. At large N_c, on the other hand, the DGR instability causes a chiral-density wave phase to dominate over the color superconducting phase. There is an alternative large N_c limit, with the quarks transforming in the two-index antisymmetric representation of the gauge group, which at N_c=3 reduces to QCD but looks quite different at large N_c. We show that in this alternative large N_c limit, the DGR instability does not occur, so that it may be plausible that the ground state of high-density quark matter is a color superconductor even when N_c is large. This revives the hope that a large N_c approximation might be useful for getting some insights into the high-density phenomenology of QCD.

8 pages, 1 figure

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• Baryons and baryonic matter in the large Nc and heavy quark limits
• Enhanced contribution of the pairing gap to the QCD equation of state at large isospin chemical potential
• Spectroscopy of SU(4) lattice gauge theory with fermions in the two index anti-symmetric representation
• Topics in Lattice QCD and Effective Field Theory
• Spin-charge separation for paired Dirac fermions in $(1+1)$ dimensions