Particle creation in varying speed of light cosmological models

Einstein's field equations with a variable speed of light c = c(t), gravita tional coupling G = G(t) and decaying vacuum energy density Lambda = Lambda (t) are considered as describing matter creation in a cosmological framewor k. The particle creation rate is uniquely determined by the variation rates of c, G and Lambda. By considering simple phenomenological evolution laws for the 'constants', exact analytical and numerical solutions of the gravit ational field equations are obtained for a homogeneous and isotropic Friedm ann-Robertson-Walker spacetime leading to a self-consistent cosmological mo del describing matter and entropy generation in the very early Universe.