A new physical interaction picture leading to the solution of the renormalization problem in the nonrelativistic treatment of the Lamb shift

By applying a self-consistent projection-operator method, developed recently by the present author, a new physical interaction picture is introduced. In this interaction picture the physically unobservable interaction of the free electron with the vacuum radiation is eliminated. Thus, a finite analytic expression for the nonrelativistic Lamb shift has been derived without using the mass renormalization concept. As explicit calculations carried out without applying the dipole approximation show, the obtained results are in agreement with the renormalized Lamb-shift results, which are usually used in the literature. In this way, for the first time to the author's knowledge, a self-consistent solution of the renormalization problem is presented.