Dynamical Mechanism for Varying Light Velocity as a Solution to Cosmological Problems

Abstract

A dynamical model for varying light velocity in cosmology is developed, based on the idea that there are two metrics in spacetime. One metric $g_{μν}$ describes the standard gravitational vacuum, and the other ${\hat g}_{μν} =g_{μν}+βψ_μψ_ν$ describes the geometry through which matter fields propagate. Matter propagating causally with respect to $\hat{g}_{μν}$ can provide acausal contributions to the matter stress-energy tensor in the field equations for $g_{μν}$, which, as we explicitly demonstrate with perfect fluid and scalar field matter models, provides a mechanism for the solution of the horizon, flatness and magnetic monopole problems in an FRW universe. The field equations also provide a ``graceful exit'' to the inflationary epoch since below an energy scale (related to the mass of $ψ_μ$) we recover exactly the standard FRW field equations.