CRITICAL-BEHAVIOR IN (2+1)-DIMENSIONAL QED WITH A 4-FERMION INTERACTION

We analyze QED(3) with a scalar-scalar type four-fermion interaction in the framework of 1/N expansion. We have derived the Dyson-Schwinger gap equation up to the next-to-leading order and determined the dynamically generated fermion mass as a function of the number of fermion flavors N and a scaled coupling theta. We observe that the critical behaviors are separated by the point theta = theta(c)* (= 2/pi(2)) and, contrary to the leading behaviors, there are mass generations even when theta greater than or equal to theta(c) with the critical flavor N-c. The critical line on the N-c - theta(c) plane is presented. We also discuss the vacuum stability of our model, and confirm that our nontrivial solutions are energetically preferred to the perturbative solution Sigma(p) = 0.