Dynamical mechanism for varying light velocity as a solution to cosmological problems

A dynamical model for varying light velocity in cosmology is developed, based on the idea that there are two metrics in spacetime. One metric gμν describes the standard gravitational vacuum, and the other ĝμν=gμν+βψμψν describes the geometry through which matter fields propagate. Matter propagating causally with respect to ĝμν can provide acausal contributions to the matter stress-energy tensor in the field equations for gμν, 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 exitʹ to the inflationary epoch since below an energy scale (related to the mass of ψμ) we recover exactly the standard FRW field equations.