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, while the other one ${\hat g}_{\mu\nu}= g_{\mu\nu}+\beta\psi_\mu\psi_\nu$, acts as a digravitational medium through which light can travel at superluminary speeds in the early universe. The modified Einstein field equations are solved for an initially flat patch of FRW universe, and an inflationary phase occurs which solves the horizon problem, the flatness problem and the relic magnetic monopole problem, ending at a phase transition time, $t_{pt}$.