Precision cosmology in modified and extended theories of gravity: An insightful test

Inflationary Cosmology in Modified Gravity Theories

We review inflationary cosmology in modified gravity such as R gravity with its extensions in order to generalize the Starobinsky inflation model. In particular, we explore inflation realized by three kinds of effects: modification of gravity, the quantum anomaly, and the R term in loop quantum cosmology. It is explicitly demonstrated that in these inflationary models, the spectral index of sca...

Modified gravity and cosmology

Non-singular Cosmology in Modified Gravity

A non-singular cosmology is derived in modified gravity (MOG). The universe begins in the distant past in a contracting de Sitter phase, is non-singular at t = 0 and then describes approximately the standard radiation dominated solution before the time of decoupling. The spacetime in the neighborhood of t = 0 is described by Minkowski spacetime in which the Weyl curvature tensor vanishes and th...

Viscous Frw Cosmology in Modified Gravity

We discuss a modified form of gravity implying that the action contains a power α of the scalar curvature. Coupling with the cosmic fluid is assumed. As equation of state for the fluid, we take the simplest version where the pressure is proportional to the density. Based upon a natural ansatz for the time variation of the scale factor, we show that the equations of motion are satisfied for gene...

Cosmological singularities and modified theories of gravity

We consider perturbative modifications of the Friedmann equations in terms of energy density corresponding to modified theories of gravity proposed as an alternative route to comply with the observed accelerated expansion of the universe. Assuming that the present matter content of the universe is a pressureless fluid, the possible singularities that may arise as the final state of the universe...