Cosmology with a new f(R) gravity model in Palatini formalism

TL;DR

This paper investigates a new f(R) gravity model in Palatini formalism as an alternative to dark energy, analyzing its cosmological behavior, compatibility with data, and distinguishing features from other models.

Contribution

It introduces and studies a novel f(R) gravity model in Palatini formalism, comparing its cosmological predictions with existing models and observational data.

Findings

The new model aligns well with luminosity distance data across parameters.

It predicts a distinct future evolution of the universe compared to other models.

Statefinder diagnostics reveal unique evolutionary trajectories for the new model.

Abstract

One of the most favourable extensions of General Relativity is the $f(R)$ gravity. $f(R)$ gravity in Palatini formalism can be a realistic alternative to the dark energy problem. In this work we study a recently introduced dark energy $f(R)$ gravity model along with two other models in cosmological perspectives under the Palatini formalism. First, we study the cosmic expansion history of these models with the help of the important cosmographic parameters, such as the Hubble parameter, luminosity distance, effective equation of state etc. This study shows that the new model behaves similarly with the other two models as well as with the $\Lambda$CDM model in some respects in the early or very early phases of the universe. It could predict the present accelerated expansion of the universe somewhat differently from the other models with a peculiar future history of the universe. Within a constrained range of parameters all models show a good agreement with the Union2.1 luminosity distance data. However, the new model shows a quite satisfactory agreement in the whole range of its allowed parameters than that of the other two models. We also obtain cosmological constraints on these models from the Observed Hubble Data. Further, models have been tested by using $Om(z)$ test and statefinder diagnostics. These diagnostics especially, the statefinder diagnostic shows that the evolutionary differences between these models are distinct. The evolutionary trajectories of the new model are completely different from the other two models we have considered.