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The logarithmic $R^2$-corrected $F(R)$ gravity is investigated as a prototype model of modified gravity theories with quantum corrections. By using the auxiliary field method, the model is described by the general relativity with a scalaron field. The scalaron field can be identified as an inflaton at the primordial inflation era. It is also one of the dark matter candidates in the dark energy era. It is found that a wide range of the parameters is consistent with the current observations of CMB fluctuations, dark energy and dark matter.
In gravity theories derived from a f(R) Lagrangian, matter is usually supposed to be minimally coupled to the metric, which hence defines a ``Jordan frame. However, since the field equations are fourth order, gravity possesses an extra degree of free
We propose a new unified model that describes~dark energy and dark matter in the context of $f(R,phi )$ gravity using a massive scalar field in five dimensions. The scalar field is considered in the bulk that surrounds the 3-brane in branworld model.
A review of the new of the problem of dark energy using modified gravity approach is considered. An explanation of the difficulties facing modern cosmology is given and different approaches are presented. We show why some models of gravity may suffer
The article presents modeling of inflationary scenarios for the first time in the $f(R,T)$ theory of gravity. We assume the $f(R,T)$ functional from to be $R + eta T$, where $R$ denotes the Ricci scalar, $T$ the trace of the energy-momentum tensor an
Using dynamical system analysis, we explore the cosmology of theories of order up to eight order of the form $f(R, Box R)$. The phase space of these cosmology reveals that higher-order terms can have a dramatic influence on the evolution of the cosmo