Scalar - Tensor gravity with scalar -matter direct coupling and its
  cosmological probe
  SNIA and CMB datasets have shown both of evolving Newton's "constant" and a
signature of the coupling of scalar field to matter. These observations
motivate the consideration of the scalar-matter coupling in Jordan frame in the
framework of scalar-tensor gravity. So far, majority of the works on the
coupling of scalar matter has performed in Einstein frame in the framework of
minimally coupled scalar fields. In this work, we generalize the original
scalar-tensor theories of gravity introducing a direct coupling of scalar to
matter in the Jordan frame. The combined consideration of both evolving
Newton's constant and scalar-matter coupling using the recent observation
datasets, shows features different from the previous works. The analysis shows
a vivid signature of the scalar-matter coupling. The variation rate of the
Newton's constant is obtained rather greater than that determined in the
previous works.
