**PERTURBATIVE QUANTUM FIELD THEORY**

**Lecturers:** Christoph Kopper, Cédric Lorcé

This course is a sequel to PHY551, *Relativistic fields and their quantisation*. It provides the conceptual tools to define perturbative quantum field theory, and some techniques to exploit its applications. We start by introducing the Feynman propagators for the different types of field equations. Then we turn to the concept of the scattering or S-matrix and introduce the LSZ reduction formulae which relate the vacuum expectation values of field operators to the S-matrix elements. We establish the Gell-Mann Low formula which paves the way towards perturbative calculations in interacting field theory.

After giving a simple proof of Wick's theorem, we deduce the Feynman rules and apply them to a few concrete examples. We end with some remarks on perturbative renormalization of quantum field theory.

**Required level:**

PHY551 - Relativistic fields and their quantisation **Course language:** English**ECTS credits:** 5

- Teaching coordinator: Christoph Kopper
- Teaching coordinator: Cédric Lorcé