Radiative Corrections of Lowest Order

In Chap. 15 we have studied some applications to physical processes by using the lowest order of perturbation theory. The next step is to compute corrections in higher order of perturbation theory. Such so-called radiative corrections suffer under the appearance of divergent algebraic Feynman integrals. Therefore, we have to use the method of renormalization in order to get finite expressions which depend on the free parameters m_eff and e_eff. These parameters must be determined by physical experiments. Typical radiative corrections in lowest possible order (so-called one-loop corrections) are:

• • the radiative correction of the Coulomb potential (Uehling 1935);

• • the Lamb shift of the spectrum of the hydrogen atom (Bethe 1947);

• • the anomalous magnetic moment of the electron (Schwinger 1947);

• • scattering of photons by photons (Euler 1936, Karpus and Neumann 1950).