Broken Scale Invariance and the Regularization of a Conformal Sector in Gravity with Wess-Zumino actions

TL;DR

This paper explores how scale invariance is broken in anomaly-induced actions within gravity, emphasizing the role of finite subtractions and renormalization schemes in understanding the trace anomaly and conformal sector regularization.

Contribution

It demonstrates that scale breaking arises from finite subtractions in renormalization, clarifying the role of regularization schemes in anomaly-induced actions in curved spacetime.

Findings

Finite subtractions determine scale breaking without nonlocal operator modifications.

Dimensional regularization and cutoff schemes reveal ambiguities in handling quantum corrections.

Scale and trace anomalies are linked to Weyl-invariant counterterms at four dimensions.

Abstract

We elaborate on anomaly induced actions of the Wess-Zumino (WZ) form and their relation to the renormalized effective action, which is defined by an ordinary path integral over a conformal sector, in an external gravitational background. In anomaly-induced actions, the issue of scale breaking is usually not addressed, since these actions are obtained only by solving the trace anomaly constraint and are determined by scale invariant functionals. We investigate the changes induced in the structure of such actions once identified in dimensional renormalization (DR) when the $\epsilon = d-4 \to 0$ limit is accompanied by the dimensional reduction (DRed) of the field dependencies. We show that operatorial nonlocal modifications $(\sim\Box^\epsilon)$ of the counterterms are unnecessary to justify a scale anomaly. In this case, only the ordinary finite subtractions play a critical role in the determination of the scale breaking. This is illustrated for the WZ form of the effective action and its WZ consistency condition, as seen from a renormalization procedure. Logarithmic corrections from finite subtractions are also illustrated in a pure $d=4$ (cutoff) scheme. The interplay between two renormalization schemes, one based on dimensional regularization (DR) and the second on a cutoff in $d=4$, illustrates the ambiguities of DR in handling the quantum corrections in a curved background. Therefore, using DR in a curved background, the scale and trace anomalies can both be obtained by counterterms that are Weyl invariant only at $d=4$.