In this paper, we study a particular modified gravity Equation of State, the so-called Jaime-Jaber-Escamilla, that emerges from the first gravity modified action principle and can reproduce three cosmological viable $f(R)$ theories: the Starobinsky, Hu-Sawicki, and Exponential models . This EoS is a suitable candidate to reproduce the dynamical dark energy behaviour already reconstructed by the current data sets. Based on the joint statistical analysis, we found that our results are still in good agreement (within $1sigma$) with the $Lambda$CDM, while at perturbative level we notice that the matter power spectrum normalisation factor $sigma_8$ shows an agreement with SDSS and SNeIa+IRAS at 1-$sigma$ for the Starobinsky model and with SDSS-vec for the Hu & Sawicki and Exponential models. Furthermore, we found that for the $H_0$ values, Starobinsky and Hu & Sawicki show the least tension in comparison with PL18 TT. All these aspects cannot be observed textit{directly} from other alternatives theories, were a equation of state is difficult to compute analytically.
Download