Coupled Clusters and Quantum Electrodynamics

Abstract

We start by reviewing, as a background, the standard non-relativistic and relativistic many-body perturbative and coupled-cluster approaches in the way we have implemented them. The covariant-evolution-operator method that we introduced more recently for quantum-electrodynamical (QED) calculations is then described, and it is demonstrated how this method can be extended to combine electron-correlation and QED effects in a covariant manner. This can be included in a many-body calculation of coupled-cluster type, and it is demonstrated that this leads for two-particle systems eventually to the full Bethe–Salpeter equation. It is indicated how this procedure can also be applied to systems with more than two electrons. Preliminary numerical results are given for the ground state of some heliumlike ions.