Is CMBR anisotropy due to fluctuations in G?

Large-angle anistropy in the Cosmic Microwave Background Radiation (CMBR) arises due to the spatial variation of the gravitational potential at the surface of last scatter. In those theories of gravity in which gravitational coupling G is a constant, gravitational potential fluctuations arise purely due to the inhomogeneities in the matter distribution. However, in the theories in which the gravitational constant is not spatially uniform, gravitational potential fluctuations will have contribution from G variations also. Extended inflationary models involve Brans-Dicke theory of gravity. In these theories, G is determined by the value of the Brans-Dicke field. Quantum fluctuations in the Brans-Dicke field lead to fluctuations in G on the surface of last scatter which in turn leads to the anisotropy in the CMBR through the variation in the gravitational potential. We calculate such fluctuations in a simple model.