Abstract

We study the definition of trace anomalies for models of Dirac and Weyl fermions coupled to a metric and a gauge potential. While in the non-perturbative case the trace anomaly is the response of the effective action to a Weyl transformation, the definition in a perturbative approach is more involved. In the latter case, we use a specific formula proposed by M.Duff, of which we present a physical interpretation. The main body of the paper consists in deriving trace anomalies with the above formula and comparing them with the corresponding non-perturbative results. We show that they coincide and stress the basic role of diffeomorphism invariance for the validity of the approach.

Highlights

  • We study the definition of trace anomalies for models of Dirac and Weyl fermions coupled to a metric and a gauge potential

  • While in the non-perturbative case the trace anomaly is the response of the effective action to a Weyl transformation, the definition in a perturbative approach is more involved

  • We use a specific formula proposed by M.Duff, of which we present a physical interpretation

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Summary

Introduction

We will consider two examples where these anomalies do appear: the even trace anomaly in the theory of a Dirac fermion, and the odd one in the theory of a Weyl fermion, both coupled to a vector potential Vμ. In both cases, we compare the results with the ones obtained via the non-perturbative heat-kernel-like method, which we refer to as the Seeley–DeWitt (SDW).

Even Parity Trace Anomalies due to Vector Gauge Field
The First Correlator
The Conformal Ward Identity
The 2-Point Current Correlator
The Second Correlator
Diffeomorphisms Are Conserved
The Seeley–DeWitt Approach
The Consistent Chiral Anomaly via SDW
The Odd Trace Anomaly via SDW
Anomalies and Diffeomorphisms
Conclusions

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