Homogeneous and Isotropic Spacetime in Conformal Scalar-Tensor Gravity

TL;DR

This paper derives the equations governing homogeneous and isotropic spacetimes in conformal scalar-tensor gravity, showing that their evolution closely parallels standard cosmology but driven by scalar field dynamics.

Contribution

It provides a detailed derivation of background and perturbation equations in conformal scalar-tensor gravity, highlighting their similarity to general relativity.

Findings

Background evolution driven by scalar field dynamics.

Perturbation equations identical to those in general relativity.

Scalar field replaces Hubble function in static spacetime.

Abstract

The background field equations for homogeneous and isotropic spacetime are derived in conformal scalar-tensor gravity. The background temporal evolution is entirely driven by the dynamical evolution of the scalar field, i.e. particle masses, and satisfies an equation which is identical in form to the Friedmann equation of the standard cosmological model in general relativity. In a static background spacetime the scalar field (logarithmic) time-derivative replaces the `Hubble function'. It is also shown that linear perturbations are governed by equations which are identical to those obtained in general relativity, but with their evolution stemming from the scalar field dynamics.