Antonio Jesús López-Revelles

arXiv2013

Reconstructing cosmic acceleration from f(R) modified gravity

A variant of the accelerating cosmology reconstruction program is developed for $f(R)$ gravity. Reconstruction schemes in terms of e-foldings and by using an auxiliary scalar field are developed. An example of a model with a transient phantom behavior without real matter is explicitly discussed in both schemes. Detailed comparison of the two schemes of reconstruction is presented. It seems to support physical non-equivalence of the two frames.

gr-qc↗

arXiv2013

Growth of matter perturbations for realistic $F(R)$ models

Two different realistic $F(R)$ modified gravity models are considered in the framework of the Friedmann-Lemetre-Robertson-Walker universe. The parameters of these two models are adjusted to reach coherence with the most recent and accurate observations of the current universe. A study of the growth of matter density perturbations is done, and several parametrizations of the growth index are developed for both models. The ansatz for the growth index given by $γ= γ_0 + γ_1 z/(1+z)$ seems to be the best parametrization for the two models considered. Finally, the values obtained for $γ_0$ and $γ_1$ can be used in order to characterize these two models and to differentiate them from others such as the Hu-Sawicki model.

gr-qc↗