Gravitational energy in Brans-Dicke cosmological models

The behaviour of gravitational energy and scalar field during the evolution of the universe within the framework of Brans-Dicke theory has been discus sed. With help of the Landau-Lifshitz pseudo-tenser for the flat Friedmann- Robertson-Walker model, it is found that (i) the total energy of the univer se is always zero, (ii) the Brans-Dicke scalar held for all omega greater t han or equal to 0 contributes energy to the negative energy of gravitationa l field and this gets transferred to the vacuum energy which accelerates th e expansion of the universe.