Realization of symmetry in the ERG approach to quantum field theory

TL;DR

This paper reviews how the exact renormalization group (ERG) approach can be used to realize and analyze symmetries in various renormalizable quantum field theories, including gauge theories and sigma models.

Contribution

It introduces formal methods to incorporate symmetries within the ERG framework and applies these to several key models, including QED, YM theories, and the Wess-Zumino model.

Findings

Demonstrates how to characterize renormalizability via ERG solutions.

Shows how to impose Ward-Takahashi identities in ERG.

Calculates axial and chiral anomalies within the ERG approach.

Abstract

We review the use of the exact renormalization group for realization of symmetry in renormalizable field theories. The review consists of three parts. In part I (sects. 2,3,4), we start with the perturbative construction of a renormalizable field theory as a solution of the exact renormalization group (ERG) differential equation. We show how to characterize renormalizability by an appropriate asymptotic behavior of the solution for a large momentum cutoff. Renormalized parameters are introduced to control the asymptotic behavior. In part II (sects. 5--9), we introduce two formalisms to incorporate symmetry: one by imposing the Ward-Takahashi identity, and another by imposing the generalized Ward-Takahashi identity via sources that generate symmetry transformations. We apply the two formalisms to concrete models such as QED, YM theories, and the Wess-Zumino model in four dimensions, and the O(N) non-linear sigma model in two dimensions. We end this part with calculations of the abelian axial and chiral anomalies. In part III (sects. 10,11), we overview the Batalin-Vilkovisky formalism adapted to the Wilson action of a bare theory with a UV cutoff. We provide a few appendices to give details and extensions that can be omitted for the understanding of the main text. The last appendix is a quick summary for the reader's convenience.