INSTANTONS AND CHIRAL-SYMMETRY RESTORATION IN QCD-LIKE THEORIES

At finite temperatures it is known that quark-induced interaction lead to formation of instanton-anti-instanton molecules, strongly polarize d in time direction. We report first direct simulations of the statist ical mechanics of the interacting instanton ensemble at finite tempera tures. First of all, they confirmed that molecule formation is driving the chiral phase transition. It happens at T similar or equal to 140 MeV (for two flavors) and is second order, while being weak first orde r if quark masses are as in QCD. We also calculated the behavior of th ermodynamics, mesonic susceptibilities and screening masses near the p hase transition: inside uncertainties, all agrees with lattice results . Furthermore, the first order phase transition lines extend further i n theories with larger number of flavors N-f for sufficiently small ma sses we have found that chiral restoration happens-at T = 0 already at N-f = 5.