Dynamical chiral symmetry breaking in unquenchedQED3

We investigate dynamical chiral symmetry breaking in unquenched ${QED}_3$using the coupled set of Dyson--Schwinger equations for the fermion and photonpropagators. For the fermion-photon interaction we employ an ansatz whichsatisfies its Ward--Green--Takahashi identity. We present self-consistentanalytical solutions in the infrared as well as numerical results for allmomenta. In Landau gauge, we find a phase transition at a critical number offlavours of $N_f^{\mathrm crit} \approx 4$. In the chirally symmetric phase theinfrared behaviour of the propagators is described by power laws withinterrelated exponents. For $N_f=1$ and $N_f=2$ we find small values for thechiral condensate in accordance with bounds from recent lattice calculations.We investigate the Dyson--Schwinger equations in other linear covariant gaugesas well. A comparison of their solutions to the accordingly transformed Landaugauge solutions shows that the quenched solutions are approximately gaugecovariant, but reveals a significant amount of violation of gauge covariancefor the unquenched solutions.Comment: 33 pages, 8 figures, reference added, version to be published in Phys. Rev.