INFRARED BEHAVIOR OF PROPAGATORS AND VERTICES

We elucidate constraints imposed by confinement and dynamical chiral s ymmetry breaking on the infrared behaviour of the dressed-quark and -g luon propagators, and dressed-quark-gluon vertex. In covariant gauges the dressing of the gluon propagator is completely specified by P(k(2) ): = 1/[1 + Pi(k(2))], where Pi(k(2)) is the vacuum polarisation. In t he absence of particle-like singularities in the dressed-quark-gluon v ertex, extant proposals for the dressed-gluon propagator that manifest P(k(2) = 0)= 0 and max(P(k(2))) similar to 10 neither confine quarks nor break chiral symmetry dynamically. This class includes all existin g estimates of P(k(2)) via numerical simulations. (C) 1998 Published b y Elsevier Science B.V. All rights reserved.