Anomalous coupling of scalars to gauge fields

TL;DR

This paper investigates how scalar-tensor theories coupled to fermions transform under Weyl rescaling, revealing a direct coupling between scalars and gauge fields that emerges when changing from Jordan to Einstein frame.

Contribution

It provides a straightforward derivation of the modified gauge couplings resulting from Weyl rescaling in scalar-tensor theories.

Findings

Identification of the direct scalar-gauge field coupling in Einstein frame

Clarification of transformation properties of scalar-tensor theories

Implications for gauge interactions in different frames

Abstract

We study the transformation properties of a scalar-tensor theory, coupled to fermions, under the Weyl rescaling associated with a transition from the Jordan to the Einstein frame. We give a simple derivation of the corresponding modification to the gauge couplings. After changing frame, this gives rise to a direct coupling between the scalar and the gauge fields.