
In this work we consider a coupled system of SchwingerDyson equations for selfenergy and vertex functions in QED_3. Using the concept of a semiamputated vertex function, we manage to decouple the vertex equation and transform it in the infrared into a nonlinear differential equation of EmdenFowler type. Its solution suggests the following picture: in the absence of infrared cutoffs there is only a trivial infrared fixedpoint structure in the theory. However, the presence of masses, for either fermions or photons, changes the situation drastically, leading to a massdependent nontrivial infrared fixed point. In this picture a dynamical mass for the fermions is found to be generated consistently. The nonlinearity of the equations gives rise to highly nontrivial constraints among the mass and effective (`running') gauge coupling, which impose lower and upper bounds on the latter for dynamical mass generation to occur. Possible implications of this to the theory of hightemperature superconductivity are briefly discussed.
