EQUIVALENCE PRINCIPLE FOR MASSIVE BODIES INCLUDING ROTATIONAL ENERGY AND RADIATION PRESSURE

The Einstein gravitational theory and the Brans-Dicke gravitational theory are investigated for the gravitational-to-inertial mass ratio (mgmi) they yield for massive systems. We examine models for stars in equilibrium but undergoing rotation or containing electromagnetic radiation. General conditions on the space-time metric of many mass sources are obtained which lead to mgmi=1 for the massive systems. It is found that mgmia 1 for a nonrotating star in the Brans-Dicke theory. The violation is of order 10-6 for the Sun. In the Brans-Dicke theory there are also contributions to mgmia1 due to the radiation content of a star. This violation is of order (radiation energy)/(stellar mass), yielding a correction of about 10-8 for the Sun. © 1969 The American Physical Society.