CRITICAL COUPLING FOR DYNAMICAL CHIRAL-SYMMETRY BREAKING WITH AN INFRARED FINITE GLUON PROPAGATOR

We compute the critical coupling constant for the dynamical chiral-sym metry breaking in a model of quantum chromodynamics, solving numerical ly the quark self-energy using infrared finite gluon propagators found as solutions of the Schwinger-Dyson equation for the gluon, and one g luon propagator determined in numerical lattice simulations. The gluon mass scale screens the force responsible for the chiral breaking, and the transition occurs only for a larger critical coupling constant th an the one obtained with the perturbative propagator. The critical cou pling shows a great sensibility to the gluon mass scale variation, as well as to the functional form of the gluon propagator.