Abstract
The growth rate of matter perturbation and the expansion rate of the Universe can be used to distinguish modified gravity and dark energy models in explaining the cosmic acceleration. The growth rate is parametrized by the growth index . We discuss the dependence of on the matter energy density and its current value for a more accurate approximation of the growth factor. The observational data, including the data of the growth rate, are used to fit different models. The data strongly disfavor the Dvali-Gabadadze-Porrati model. For the dark energy model with a constant equation of state, we find that and . For the model, we find that . For the Dvali-Gabadadze-Porrati model, we find that .
- Received 12 August 2008
DOI:https://doi.org/10.1103/PhysRevD.78.123010
©2008 American Physical Society