chi variable-speed-of-light cosmologies

Variable-speed-of-light (VSL) cosmologies are currently attracting much int erest as a possible alternative to cosmological inflation. We discuss the f undamental geometrodynamic aspects of VSL cosmologies, and provide several alternative implementations. These implementations provide a large class of VSL cosmologies that pass the zeroth-order consistency tests of being comp atible with both classical Einstein gravity and low-energy particle physics . While they solve the "kinematic" puzzles as well as inflation does, VSL c osmologies typically do not solve the flatness problem since in their pures t form no violation of the strong energy condition occurs. Nevertheless, th ese models are easy to unify with inflation.