Phantom-like behavior in f (R)-gravity

We investigate possible realization of the phantom-like behavior in the framework of f (R)-gravity models where there are no phantom fields in the matter sector of the theory. By adopting some observationally reliable ansatz for f (R), we show that it is possible to realize phantom-like behavior in f (R)-gravity Without introduction of phantom fields that stiffer front instabilities and violation of the null energy condition. Depending on the choice of f (R), the null energy condition is fulfilled in some subspaces of each model parameter space. (C) 2009 Elsevier B.V. All rights reserved.