Testing f(R)-theories using the first time derivative of the orbital period of the binary pulsars

In this paper we use one of the Post-Keplerian parameters to obtain constraints on f(R)-theories of gravity. Using Minkowskian limit, we compute the prediction of f(R)-theories on the first time derivative of the orbital period of a sample of binary stars, and we use our theoretical results to perform a comparison with the observed one. Selecting a sample of relativistic binary systems we estimate the parameters of an analytic f(R)-gravity. We find that the theory is not ruled out if we consider only the double neutron star systems, and in this case we can cover the existing gap between the General Relativity prediction and the observed data.