QED${}_{2+1}$ radiation effects in a strong magnetic field

We develop the eigenfunction method for the Dirac operator in a background magnetic field in the $(2+1)$-dimensional quantum electrodynamics (QED${}_{2+1}$). In the eigenfunction representation, we find the exact solutions and the Green's functions of the Dirac equation in a strong constant homogeneous magnetic field in $2+1$ dimensions. In the one-loop QED${}_{2+1}$ approximation, we derive the effective Lagrangian, the density of vacuum fermions induced by the field, and the electron mass operator in a homogeneous background magnetic field.