Logarithmic corrected F(R)F(R) gravity in the light of Planck 2015

In this letter, we consider the theory of $F(R)$ gravity with the lagrangian density $\pounds = R+\alpha R^2 + \beta R^2 \ln \beta R$. We obtain the constant curvature solutions and find the scalar potential of the gravitational field. We also obtain the mass squared of a scalaron in the Einstein$^,$s frame. We find cosmological parameters corresponding to the recent Plank 2015 results. Finally, we analyze the critical points and stability of the new modified theory of gravity and find that logarithmic correction is necessary to have successful model.Comment: arXiv admin note: text overlap with arXiv:1502.00659 by other author

Phenomenological Fluids from Interacting Tachyonic Scalar Fields

In this paper we are interested to consider mathematical ways to obtain different phenomenological fluids from two-component Tachyonic scalar fields. We consider interaction between components and investigate problem numerically. Statefinder diagnostics and validity of the generalized second law of thermodynamics performed and checked. We suppose that our Universe bounded by Hubble horizon.Comment: 12 page