Quantum Theory of Radiation

Abstract

The understanding of radiative atomic and nuclear transitions makes it necessary to develop a quantum theory of radiation, and this in turn requires the concept of a quantized field. In a rigorous treatment of this problem, one starts with equations covariant under the Poincaré group, describing the interaction of matter and light, and subsequently one proceeds to quantize them in a covariant manner. A treatment along these lines is far beyond the scope of this book, and the interested reader is referred to the books by Akhiezer and Berestestky [AB 65], Bogolyubov and Shirkov [BS 59], Heitler [HE 54], Jauch and Rohrlich [JR 55], Thirring [TH 55] and Itzykson and Zuber [IZ 80] among others. In order to make the presentation as simple as possible, we follow a method similar to the ones used in the study of the quantum theory of many particle systems. The price to pay for this simplification, is the loss of apparent relativistic invariance of the theory.