Growth index of DGP model and current growth rate data

Recently, some efforts focus on differentiating dark energy and modified gravity with the growth function delta(z). In the literature, it is useful to parameterize the growth rate f d ln delta/d ln a = Omega(gamma)(m) with the growth index gamma. In this Letter, we consider the general DGP model with any Omega(k). We confront the growth index of DGP model with currently available growth rate data and find that the DGP model is still consistent with it. This implies that more and better growth rate data are required to distinguish between dark energy and modified gravity. (C) 2008 Elsevier B.V. All rights reserved.