A 5D NONCOMPACT KALUZA–KLEIN COSMOLOGY IN THE PRESENCE OF NULL PERFECT FLUID

For the description of the early inflation and acceleration expansion of the universe that are compatible with observational data, the 5D noncompact Kaluza–Klein cosmology is investigated. It is proposed that the 5D space is filled with a null perfect fluid, resulting in a perfect fluid in a 4D universe, plus one along the fifth dimension. By analyzing the reduced field equations for the flat FRW model, we show the early inflationary behavior and the current acceleration of the universe.