More on the dilatonic Einstein-Gauss-Bonnet gravity

TL;DR

This paper investigates Einstein-Gauss-Bonnet gravity with a dynamical dilaton, highlighting issues with frame transformations and proposing a canonical form for the dilaton's kinetic term to address nonminimal couplings.

Contribution

It introduces a modified Einstein frame with a canonical dilaton kinetic term to resolve nonminimal coupling issues in dilatonic Einstein-Gauss-Bonnet gravity.

Findings

Standard frame change does not fix nonminimal couplings.

A modified Einstein frame with a canonical dilaton kinetic term is proposed.

The new frame resolves issues related to the dynamical dilaton.

Abstract

Einstein-Gauss-Bonnet gravity coupled to a dynamical dilaton is examined from the viewpoint of Einstein's equivalence principle. We point out that the usual frame change that applies to the action without curvature correction does not cure the problem of nonminimal couplings by the dynamical nature of a dilaton field. Thus a modification of the Einstein frame is required. It is proposed that the kinetic term of a dilaton should be brought to a canonical form, which completely fixes the additional terms associated with the frame transformation.