QED positronium and the exact renormalization group

Quantum electrodynamics (QED) is studied in the framework of the exact (functional) renormalization group (ERG). This is done using an approach to these equations which employs dimensional regularization. Simultaneous solutions of the ERG equations and Ward identities are considered. An approach to the study of bound states at long distances in the ERG is employed to describe the positronium. This is done by introducing a real scalar field which describes that bound state. The flow equations are studied using an effective action ansatz and a low-momentum expansion.