Simple cosmological model with inflation and late times acceleration
Astronomical Observatory, Jagiellonian University, Orla 171, 30-244, Kraków, Poland
2 Mark Kac Complex Systems Research Centre, Jagiellonian University, ul. Łojasiewicza 11, 30-348, Kraków, Poland
* e-mail: email@example.com
Accepted: 9 March 2018
Published online: 22 March 2018
In the framework of polynomial Palatini cosmology, we investigate a simple cosmological homogeneous and isotropic model with matter in the Einstein frame. We show that in this model during cosmic evolution, early inflation appears and the accelerating phase of the expansion for the late times. In this frame we obtain the Friedmann equation with matter and dark energy in the form of a scalar field with a potential whose form is determined in a covariant way by the Ricci scalar of the FRW metric. The energy density of matter and dark energy are also parameterized through the Ricci scalar. Early inflation is obtained only for an infinitesimally small fraction of energy density of matter. Between the matter and dark energy, there exists an interaction because the dark energy is decaying. For the characterization of inflation we calculate the slow roll parameters and the constant roll parameter in terms of the Ricci scalar. We have found a characteristic behavior of the time dependence of density of dark energy on the cosmic time following the logistic-like curve which interpolates two almost constant value phases. From the required numbers of N-folds we have found a bound on the model parameter.
© The Author(s), 2018