INSTANTONS AND THE CHIRAL PHASE-TRANSITION

We examine the role of instantons in the zero-temperature chiral phase transition in an SU(N) gauge theory. For a range of N-f (the number o f fermion flavors) depending on N, the theory exhibits an infrared fix ed point at coupling alpha. As N-f decreases, alpha* increases, and i t eventually exceeds a critical value sufficient to trigger chiral sym metry breaking. For the case N = 2, we estimate the critical values of N-f and alpha, due to instantons by numerically solving a gap equati on with an instanton-generated kernel. We find instanton effects of st rength comparable to that of gluon exchange. (C) 1997 Published by Els evier Science B.V.