Cutoff dependence of self-consistent solutions in unquenched QED3

In the leading order of the 1/N expansion for the vacuum polarization, we obtain the chiral-symmetry-breaking solutions of the Schwinger-Dyson equation in three-dimensional QED with N four-component Dirac fermions. Special attention is paid on the critical number of the fermion flavor Nc and the scaling law for the dynamical fermion mass. In this framework we introduce the infrared cutoff as well as the ultraviolet one. We show the relation between the vertex ansatz and the scaling law which is consistent with our numerical results that the scaling law is affected by the infrared cutoff. Especially in the case of the Pennington and Webb's vertex ansatz, the mean-field type scaling law and cutoff-dependent finite Nc are obtained in the large infrared cutoff, while the exponential type scaling and infinite Nc are given in the sufficiently small infrared cutoff. The connection with the Monte Carlo simulation is discussed. (author)