Reza Saffari

f ( R ) gravity: From the Pioneer anomaly to cosmic acceleration

We use metric formalism in

Exact solutions of three-dimensional black holes: Einstein gravity versus F(R) gravity

f(R)

An f(R) gravitation for galactic environments

modified gravity to study the dynamics of various systems from the solar system to the cosmological scale. We assume an ansatz for the derivative of action as a function of distance and describe the Pioneer anomaly and the flat rotation curve of the spiral galaxies. Having the asymptotic behavior of action, we propose the action of

Consistency Condition of Spherically Symmetric Solutions in f(R) Gravity

f(R)=(R+\ensuremath{\Lambda})(1+\mathrm{ln}(R/{R}_{c})/(R/{R}_{0}+2/\ensuremath{\alpha}))

Vacuum solution of a linear red-shift based correction in f (R) gravity

where in galactic and solar system scales it can recover our desired form. The vacuum solution of this action also results in a positive late time acceleration for the Universe. We fix the parameters of this model, comparing with the Pioneer anomaly, rotation curve of spiral galaxies, and supernova type Ia gold sample data.

Detailed study of geodesics in the Kerr-Newman-(A)dS spacetime and the rotating charged black hole spacetime in

In this paper, we consider Einstein gravity in the presence of a class of nonlinear electrodynamics, called power Maxwell invariant (PMI). We take into account

f(R)

(2+1)

gravity

-dimensional spacetime in Einstein-PMI gravity and obtain its black hole solutions. Then, we regard pure

Geodesic equations in the static and rotating dilaton black holes: Analytical solutions and applications

F(R)

Analytical solutions of the geodesic equation in the spacetime of a black hole in f(R) gravity

gravity as well as