F(R) cosmology from Noether's symmetry

A general approach for finding exact cosmological solutions in f(R) gravity is discussed. Instead of taking into account phenomenological models, we assume, as a physical criterion, the existence of Noether symmetries in the cosmological f(R) Lagrangian. As a result, the presence of such symmetries leads to the selection of viable models and allows us to solve the equations of motion. We discuss also the case in which no Noether charge is present but general criteria can be used to achieve solutions. © 2008 IOP Publishing Ltd. and SISSA