Latest supernovae constraints on f(R) cosmologies

A class of modified gravity, known as f(R)-gravity, has presently been applied to Cosmology as a realistic alternative to dark energy. In this Letter we use the most recent Type-Ia Supernova (SNe Ia) data, the so-called Union sample of 307 SNe Ia, to place bounds on a theory of the form f(R)=R−β/Rn within the Palatini approach. Given the complementarity of SNe Ia data with other cosmological observables, a joint analysis with measurements of baryon acoustic oscillation peak and estimates of the CMB shift parameter is also performed. We show that, for the allowed intervals of n, Ωmo, and β, models based on f(R)=R−β/Rn gravity in the Palatini approach can produce the sequence of radiation-dominated, matter-dominated, and accelerating periods without need of dark energy.