New views on classical and quantum Brans-Dicke theory
  The Brans-Dicke action is one of the most natural extensions of the Einstein-Hilbert action. It is based on the introduction of a fundamental scalar field that effectively incorporates a dynamics to the gravitational coupling $G$. In spite of the diverse motivations and the rich phenomenology that comes from its solutions, Solar System tests impose strong constraints on the Brans-Dicke theory, rendering it indistinguishable from General Relativity. In the present text, new perspectives for the Brans-Dicke theory are presented, based on the possibility that the scalar field presented in the BD theory can be external, as well as on the applications to black hole physics and the primordial universe. 
J\'ulio C. Fabris, Bertrand Chauvineau, Davi C. Rodrigues, Carla R.   Almeida and Oliver F. Piattella
gr-qc astro-ph.CO hep-th