**algebraic quantum field theory** (perturbative, on curved spacetimes, homotopical)

**quantum mechanical system**, **quantum probability**

**interacting field quantization**

A Feynman diagram without external edges is called a *vacuum diagram*.

For example the simplest vacuum diagram obtained from the electron-photon interaction in quantum electrodynamics is

In the computation of scattering amplitudes in a stable vacuum the contribution of the vacuum diagrams to the Feynman perturbation series cancels out.

For details see at *S-matrix* this section

Last revised on May 17, 2019 at 20:09:00. See the history of this page for a list of all contributions to it.