Abstract
We study the growth of matter density perturbations for a number of viable gravity models that satisfy both cosmological and local gravity constraints, where the Lagrangian density is a function of the Ricci scalar . If the parameter today is larger than the order of , linear perturbations relevant to the matter power spectrum evolve with a growth rate ( is the scale factor) that is larger than in the model. We find the window in the free parameter space of our models for which spatial dispersion of the growth index ( is the redshift) appears in the range of values , as well as the region in parameter space for which there is essentially no dispersion and converges to values around . These latter values are much lower than in the model. We show that these unusual dispersed or converged spectra are present in most of the viable models with larger than the order of . These properties will be essential in the quest for modified gravity models using future high-precision observations and they confirm the possibility to distinguish clearly most of these models from the model.
- Received 19 August 2009
DOI:https://doi.org/10.1103/PhysRevD.80.084044
©2009 American Physical Society