Conformal Anomaly in 4D Gravity-Matter Theories Non-minimally Coupled with Dilaton

TL;DR

This paper systematically studies the conformal anomaly in 4D gravity-matter theories with non-minimal dilaton coupling, revealing how the dilaton influences the anomaly differently for scalar, spinor, and vector fields, and providing practical anomaly formulas.

Contribution

It introduces explicit conformal anomaly formulas for various matter fields in gravity-dilaton backgrounds and analyzes the dilaton's role in modifying the anomaly structure.

Findings

Dilaton adds a new invariant $I_4$ for scalars.

Dilaton does not alter the anomaly for spinors.

Dilaton introduces three new invariants $I_4, I_2, I_1$ for vectors.

Abstract

The conformal anomaly for 4D gravity-matter theories, which are non-minimally coupled with the dilaton, is systematically studied. Special care is taken for: rescaling of fields, treatment of total derivatives, hermiticity of the system operator and choice of measure. Scalar, spinor and vector fields are taken as the matter quantum fields and their explicit conformal anomalies in the gravity-dilaton background are found. The cohomology analysis is done and some new conformal invariants and trivial terms, involving the dilaton, are obtained. The symmetry of the constant shift of the dilaton field plays an important role. The general structure of the conformal anomaly is examined. It is shown that the dilaton affects the conformal anomaly characteristically for each case: 1)[Scalar] The dilaton changes the conformal anomaly only by a new conformal invariant, $I_4$; 2)[Spinor] The dilaton does {\it not} change the conformal anomaly; 3)[Vector] The dilaton changes the conformal anomaly by three new (generalized) conformal invariants, $I_4,I_2,I_{1}$. We present some new anomaly formulae which are useful for practical calculations. Finally, the anomaly induced action is calculated for the dilatonic Wess-Zumino model. We point out that the coefficient of the total derivative term in the conformal anomaly for the 2D scalar coupled to a dilaton is ambiguous. This resolves the disagreement between calculations in refs.\cite{ENO,NO,SI97,KLV} and the result of Hawking-Bousso\cite{BH}.