Toward the quantitative theory of the instanton liquid (III). Instantons and light fermions

The interaction of pseudoparticles due to light-quark exchange strongly affects the structure of the instanton liquid. At large enough N_f{hook}, these modifications are so strong that the density of the small-size instanton molecules is ultraviolet divergent. Using some simplified models, we study how the (chirally asymmetric) polymer phase is changed to the (symmetric) molecular phase as the pseudoparticle density is lowered. We have made the full-scale simulations for the SU(2) theory with quarks, and have found that instantons do generate the quark condensate in its vacuum.