nLab
tadpole

Contents

Context

Algebraic Qunantum Field Theory

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

Introduction

Concepts

field theory:

Lagrangian field theory

quantization

quantum mechanical system, quantum probability

free field quantization

gauge theories

interacting field quantization

renormalization

Theorems

States and observables

Operator algebra

Local QFT

Perturbative QFT

Contents

Idea

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.

Examples

References

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 March 19, 2019 at 01:05:44. See the history of this page for a list of all contributions to it.