Dual Nature of the Ricci Scalar, Creation of Spinless and Spin-1/2   Particles as Well as a New Cosmological Scenario I
  In earlier papers, it is found that the Ricci scalar behaves in dual manner (i) like a matter field and (ii) like a geometrical field. Using dual role of the Ricci scalar, inhomogeneous cosmological models are derived. The essential features of these models is capability of these to exhibit gravitational effect of compact objects also in an expanding universe. Here, production of spinless and spin-1/2 particles are demonstrated in these models. 
S. K. Srivastava