Preface to Second Edition

In this second revised edition several parts of the first edition have been rewritten and extended. This is particularly the case for Chaps. 4, 6 and 8, which represent the central parts of the book. The presentation of numerical results concerning quantum-electrodynamical (QED) effects in combination with electron correlation is extended and now includes radiative QED effects (electron self-energy, vertex correction and vacuum polarization), involving the use of Feynman and Coulomb gauges. A new section (Part IV) has been added, dealing with QED effects in dynamical processes. It turned out that the Green’s operator, introduced primarily for structure problems, is particularly suitable also for dealing with dynamical processes, when bound states are involved. Here, certain singularities may appear of the same kind as in dealing with static processes, leading to so-called model-space contributions. These cannot be handled with the standard S-matrix formulation, which is the normal procedure for dynamical processes involving only free-particle states. This has led to a modification of the optical theorem applicable also to bound states, where the S-matrix is replaced by the Green’s operator. In addition, a number of misprints and other errors have been corrected for, and I am grateful to all readers who have pointed out some of them to me. I wish to express my gratitude to Prof. Walter Greiner, Frankfurt, and to the Alexander von Humboldt Foundation for moral and economic support during the entire work with this book. I am very grateful to my coworkers, Sten Salomonson, Daniel Hedendahl and Johan Holmberg, for valuable cooperation and for allowing me to include results that are unpublished or in the process of being published.