Cosmological particle production in five-dimensional Kaluza-Klein theory

The five-dimensional induced-matter theory is reformulated to describe matter and entropy creation in the very early Universe, in the presence of a variable speed of light and gravitational constant. The five-dimensional vacuum field equations induce a four-dimensional cosmological fluid with the particle creation rate being determined by the time variation rate of the metric tensor component of the fifth dimension. For a homogeneous and isotropic flat Friedmann-Robertson-Walker geometry exact analytical solutions of the five-dimensional gravitational field equations are obtained, leading to a self-consistent cosmological model describing matter and entropy generation from the extra dimensions.