Cosmological consequences of Brans–Dicke theory in 4D from 5D scalar-vacuum

We study 5D Brans–Dicke theory in the framework of (gravitational) baryogenesis and primordial light element formation. Such a model is able to explain the present cosmic accelerated expansion without recurring to matter fields in 5D or dark energy in 4D. In fact, the 5D to 4D reduction arises a space-matter tensor of geometrical origin that plays the role of a new ingredient on-shell. For an isotropic and homogeneous Universe, the cosmological equations admit a power-law solution of the scale factor, a(t)∼ t^α , we constrain the exponential factor α by using the present bounds on the matter–antimatter asymmetry in the Universe and Big Bang Nucleosynthesis. A possible connection with dark matter relic abundance is also discussed.