Instanton-induced interactions in finite density QCD: from chiral symmetrybreaking to colour superconductivity

We consider the finite density, zero-temperature behaviour of quark matter in the instanton picture. Since the instanton-induced interactions are attr active in both (q) over bar q and 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 'colour s uperconductor', at finite density.