Cosmology with Hu-Sawicki gravity in Palatini Formalism
  Cosmological models based on f(R)-gravity may exhibit a natural acceleration mechanism without introducing a dark energy component. In this paper, we investigate cosmological consequences of the so-called Hu-Sawicki f(R)-gravity in the Palatini formalism. We derive theoretical constraints on the model parameters and perform a statistical analysis to determine the parametric space allowed by current observational data. We find that this class of models is indistinguishable from the standard \Lambda CDM model at the background level. Differently, from previous results in the metric approach, we show that these scenarios are able to produce the sequence of radiation-dominated, matter-dominated, and accelerating periods without need of dark energy. 
B. Santos, M. Campista, J. Santos, J. S. Alcaniz
astro-ph.CO gr-qc hep-ph