Propagators and Scattering Theory

Abstract

In this course we will deal with quantum electrodynamics (QED), which is one of the most successful and most accurate theories known in physics. QED is the quantum field theory of electrons and positrons (the electron–positron field) and photons (the electromagnetic or radiation field). The theory also applies to the known heavy leptons (μ and τ) and, in general, can be used to describe the electromagnetic interaction of other charged elementary particles. However, these particles are also subject to nonelectromagnetic forces, i.e. the strong and the weak interactions. Strongly interacting particles (hadrons) are found to be composed of other particles, the quarks, so that new degrees of freedom become important (colour, flavour). It is believed that on this level the strong and weak interactions can be described by “non-Abelian” gauge theories modelled on QED, which is the prototype of an “Abelian” gauge theory. These are the theories of quantum chromodynamics (QCD) for the strong interaction and quantum flavourdynamics for the weak interaction. In this course we will concentrate purely on the theory of QED in its original form. Quantum electrodynamics not only is the archetype for all modern field theories, but it also is of great importance in its own right since it provides the theoretical foundation for atomic physics.