Understand
We study the appearance of anomalies of the Master Ward Identity, which is a universal renormalization condition in perturbative QFT.
- The main insight of the present paper is that any violation of the Master Ward Identity can be expressed as a LOCAL interacting field; this is a version of the well-known Quantum Action Principle of Lowenstein and Lam.
- Proceeding in a proper field formalism by induction on the order in $\hbar$, this knowledge about the structure of possible anomalies as well as techniques of algebraic renormalization are used to remove possible anomalies by finite renormalizations.
- As an example the method is applied to prove the Ward identities of the O(N) scalar field model.
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