Tag Archive for: perturbation theory

Virtual Particles Explained — Quantum Field Theory
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Definition / Summary
Virtual particles are a mathematical device used in perturbation expansions of the S-operator (transition matrix) for interactions…

Learn Interacting Quantum Fields in Mathematical Quantum Field Theory
This is one chapter in a series on Mathematical Quantum Field Theory.The previous chapter is 14. Free quantum fields.The next chapter is 16. Renormalization.
15.…

Introduction to Perturbative Quantum Field Theory
This is the beginning of a series that gives an introduction to perturbative quantum field theory (pQFT) on Lorentzian spacetime backgrounds in its…

Introduction to Causal Perturbation Theory
Relativistic quantum field theory is notorious for the occurrence of divergent expressions that must be renormalized by recipes that on first sight sound…

Why Renormalisation in Quantum Theory Needs a Cutoff
Introduction
This is a follow on from my paper explaining renormalization. A question was raised - why exactly do we need a cut-off. There is a deep reason…
