effective action functional


Variational calculus


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In the context of quantum field theory an effective action is an object obtained from a more fundamental action functional by “averaging out” the dependency on certain variables.

There are two different notions of effective action

  1. The one-particle irreducible action (“1PI action”);

  2. The Wilsonian effective action of effective quantum field theory.

1PI action


Wilsonian effective action



A discussion (with an eye towards supersymmetric quantum field theory and Seiberg duality) is in section 2.1 of

  • Flip Tanedo, Notes on Seibergology (pdf)

A review of effective actions in the background field formalism is in section 3.1 of

  • Darren Trevor Grasso, Higher order contributions to the effective action of 𝒩=2\mathcal{N} = 2 and 44 supersymmetric Yang-Mills theories from heat kernel techniques in superspace Thesis (2007) (web)

Revised on October 24, 2011 14:02:15 by Urs Schreiber (