Light quarks in the instanton vacuum at finite baryon density

Abstract

We consider the finite density, zero-temperature behavior of quark matter in the instanton picture. Since the instanton-induced interactions are attractive in both $\overline{q}q$ and $\mathrm{qq}$ channels, a competition ensues between phases of matter with condensation in either or both. It results in chiral symmetry restoration due to the onset of diquark condensation, a “color superconductor,” at finite density. Also possible is a state with both manners of condensation; however, such a phase is at best metastable for any chemical potential. The properties of quark matter in each phase are discussed, with emphasis on the microscopic effects of the effective mass and superconducting energy gap.