Homogeneous and Isotropic Spacetime in Conformal Scalar-Tensor Gravity

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.