PHASE-STRUCTURE OF UNQUENCHED QED WITH 4-FERMION INTERACTION

The chiral-symmetry-breaking phase transition of massless QED with chiral-invariant four-fermion interaction is studied through the Schwinger-Dyson equation, taking into account the vacuum polarization effect of the photon propagator. We determine the structure of the phase diagram, the critical line and the scaling relation for the dynamical fermion mass and the chiral order parameter in the neighborhood of the critical line. Our results are consistent with the mean-field behavior and there is no compelling evidence for an interacting continuum limit.