Gauge invariance of quantum electrodynamics of multi-electron atoms

Abstract

The proof of gauge invariance of the quantum electrodynamics of photons and electrons does not apply directly to the quantum electrodynamics of photons, electrons, and nuclei because multi-electron atoms belong to the space of asymptotic states of the extended theory. We offer two possible ways to circumvent this problem and prove, using a fairly general model for the description of nucleon-nucleon interaction in nuclei, the gauge invariance of the masses and electromagnetic form factors of multi-electron atoms in all orders of perturbation theory.