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 g(mu nu) describes the standard gravitational vacuum, and the other (g) over cap(mu nu) = g(mu nu) + beta psi(mu)psi(nu) describes the geometry through which matter fields propagate. Matter propagating causally with respect to (g) over cap(mu nu) can provide acausal contributions to the matter stress-energy tensor in the field equations for g(mu nu), 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 psi(mu)) we recover exactly the standard FRW field equations. (C) 1999 Published by Elsevier Science B.V. All rights reserved.