Flavor mixing in the instanton vacuum

The SU(2) instanton vacuum is investigated beyond the dilute gas approximation, using Langevin simulation techniques to average over the set of collective coordinates. Both cases of zero and finite current quark masses are studied. At high density the vacuum state exhibits the characteristics of a liquid phase of instantons and anti-instantons. In this phase chiral symmetry is spontaneously broken in agreement with Shuryak's recent investigation. For more than one flavor a mixed liquid-gas phase is observed at low density with a strong tendency for chiral symmetry restoration. Within the limitations of our model, we study the effect of the strange mass on the chiral condensate of the light quarks. Our results suggest that the coupling between strange and up-down quarks is due to the mass dependence of the average size and density of the pseudoparticles. In a constituent quark model picture, the same conclusion holds for the strangeness admixture in the nucleon state at zero momentum transfer. Finally, in the quenched approximation we derive an effective action in terms of delocalized fermions for one, two and three flavors. In the mean field approximation, we find that the coupling between flavors is strongly suppressed. (orig.)