Quantum field theory

Summary

Quantum field theory (QFT) is the framework that combines quantum mechanics with special relativity by quantizing fields instead of particles. Particles appear as excitations of the fields, and their number can change. The Fock space of free particles is the simplest example of its state spaces. It is the language of the Standard Model of particle physics and of much of condensed matter physics. Its computations are organized by path integrals, Feynman diagrams and renormalization. Mathematically, axiom systems such as the Wightman axioms and the Haag–Kastler axioms make the notion precise. No interacting theory in four spacetime dimensions is yet known to satisfy them.