Geometrodynamics of variable-speed-of-light cosmologies - art. no. 103518

Variable-speed-of-light (VSL) cosmologies are currently attracting interest as an alternative to inflation. We investigate the fundamental geometrodyn amic aspects of VSL cosmologies and provide several implementations which d o not explicitly break Lorentz invariance (no "hard'' breaking). These ''so ft'' implementations of Lorentz symmetry breaking provide particularly clea n answers to the question "VSL with respect to what?." The class of VSL cos mologies,vr consider are compatible with both classical Einstein gravity an d low-energy particle physics. These models solve the "kinematic" puzzles o f cosmology as well as inflation does, but cannot by themselves solve the f latness problem, since in their purest form no violation of the strong ener gy condition occurs. We also consider a heterotic model (VSL plus inflation ) which provides a number of observational implications for the low-redshif t universe if chi contributes to the ''dark energy" either as CDM or quinte ssence. These implications include modified gravitational lensing, birefrin gence, variation of fundamental constants and rotation of the plane of pola rization of light from distant sources.