Real Life II: Fermions and QED

Abstract

The formalism of quantum field theory we have developed in the previous chapters allows us to think of (what we usually call) particles as quantum excitations of (what we usually call) fields. The clearest example is that of a photon which arises as an excitation of the electromagnetic field. We have also discussed how we can describe the interaction of the particles, say, e.g., their scattering, starting from a field theoretical description. We did all these using a scalar field and the electromagnetic field as prototypes.