POSITRONIUM STATES IN 3-DIMENSIONAL QED

The e(-)-e(+) bound state spectrum of three-dimensional QED is investi gated in the quenched ladder approximation to the homogeneous Bethe-Sa lpeter equation with fermion propagators from a rainbow approximation Schwinger-Dyson solution with a variable fermion mass. A detailed anal ysis of the analytic structure of the fermion propagator is performed so as to test the appropriateness of the methods employed. The large f ermion mass limit of the Bethe-Salpeter equation is also considered, i ncluding a derivation of the Schrodinger equation, and comparisons are made with existing nonrelativistic calculations.