Introduction

Abstract

The study of relativistic processes is based on collision phenomena at energies much larger than the rest energies of the particles involved. In this regime, a large number of new particles is typically produced, with large momenta, or, equivalently, small wavelengths. For this reason, the scheme of ordinary Quantum Mechanics, based on the Schrödinger equation for wave functions that depend on a fixed number of variables, is no longer applicable. A suitable framework is rather provided by electromagnetism, that describes radiation phenomena, and therefore the production and absorption of photons. This analogy leads in a natural way to field theory, in which the dynamical variables that describe a given physical system are fields, i.e. variables labelled by the space coordinates, and independent of each other.