tadpole

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

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

**interacting field quantization**

In *perturbative quantum field theory* a *tadpole* is a contribution to the S-matrix/scattering amplitude corresponding to a Feynman diagram which contains an edge that connects some vertex with itself.

Typically tadpoles are required to be absent. For instance the construction of time-ordered products in causal perturbation theory via the “star product” induced by the Feynman propagator (see there) implies that tadpoles are absent.

Discussion in context of causal perturbation theory/perturbative AQFT is in

- Kai Keller, around p. 30 of of
*Dimensional Regularization in Position Space and a Forest Formula for Regularized Epstein-Glaser Renormalization*, PhD thesis (arXxiv:1006.2148)

Last revised on October 4, 2019 at 06:40:10. See the history of this page for a list of all contributions to it.