RW models with variable G and constant active gravitational mass

The incorporation of the conservation of active gravitational mass in Einstein's theory demands the variation of G or Λ for baryonic matter. If G is allowed to vary, keeping Λ constant, this demands Λ≤0. For Λ<0, the model uniquely determines the curvature parameter κ=-1 with a sinusoidal expansion. An interesting case arises when Λ=0. In this case, G is a decreasing function of time in the early universe and became constant as the universe turns matter dominated reducing the models to the standard FRW models in the present phase of evolution