Physical interpretations for radiative corrections in the non-relativistic limit

Abstract
A detailed physical discussion of the contribution of non-relativistic modes of the radiation field to electron radiative corrections (Lamb shift, g-2) is presented. It is shown that these corrections can be described by a simple effective Hamiltonian, derived from a single-particle theory, and that two main physical effects are involved: the vibration of the electron charge and spin moment due to vacuum fluctuations, and the radiation reaction of the charge. It is found that the positive sign of g-2 is entirely due to the radiation reaction which slows down the cyclotron motion, whereas the Lamb shift results from the averaging of the Coulomb potential by the vibrating electron (Welton's picture). Many-particle effects and the contributions of relativistic modes are briefly discussed. They do not seem to alter these conclusions.