PPN limit and cosmological gravitational waves as tools to constrain f(R)-gravity

We discuss the PPN Solar-System constraints and the GW stochastic background considering some recently proposed f(R) gravity models which satisfy both cosmological and stability conditions. Using the definition of PPN-parameters gamma and beta in terms of f(R)-models and the definition of scalar GWs, we compare and discuss if it is possible to search for parameter ranges of f(R)-models working at Solar System and GW stochastic background scale. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim