Quantum Electrodynamics (QED) in Strong Coulomb Fields: Charged Vacuum, Atomic Clock, and Narrow Positron Lines

Abstract

Slow collisions of two heavy atoms or ions offer a unique laboratory for the study of the motion of electrons, and the behaviour of the QED vacuum, in very strong electric fields. It is for this reason that the theoretical and experimental aspects of such collisions have been studied very intensely during the last two decades. Early on, theory focussed on the change of the vacuum state from a neutral to a charged realization at a critical nuclear charge Z c = 173, and the associated spontaneous emission of positrons of well-defined energy. Later, the view broadened into the quest of gaining an understanding of dynamic phenomena caused by the time-dependence of the collision process, e.g. dynamically induced pair production, K-shell ionization, and delta-electron production. This will be discussed in the first part of my lectures, however rather concisely, because an extensive treatise of this subject exists [l].KeywordsNeutral ParticleStrong Electric FieldCollision SystemPositron SpectrumBremsstrahlung Cross SectionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.