Fermions in Brans-Dicke cosmology

Using the Brans-Dicke theory of gravitation we put under investigation a hypothetical universe filled with a fermionic field (with a self-interaction potential) and a matter constituent ruled by a barotropic equation of state. It is shown that the fermionic field [in combination with the Brans-Dicke scalar field $\phi (t)$] could be responsible for a final accelerated era, after an initial matter dominated period.

Figure 1

Brans-Dicke scalar field vs time $t$.

Figure 2

Acceleration vs time $t$.

Figure 3

Energy densities of fermionic ${\rho }_f$ and matter ${\rho }_m$ fields vs time $t$.