ABSTRACT
We arrive now at the quantum field. This is introduced at the level of a simple field – the harmonic oscillator. The classical harmonic oscillator is quantised using two methods: a canonical method and an easier, operator method – the latter developed by Dirac. It is shown how particles, such as the electron and the photon, arise as oscillations in their respective fields.
A result of this quantisation is the development of two quantities: the propagator and the interaction factor. These will be used in the next chapter to explain the meaning of a Feynman diagram.
