Constraining modified growth patterns with tomographic surveys

Viable models of modified gravity designed to produce cosmic acceleration at the current epoch, closely mimic the ΛCDM model at the level of background cosmology. However, this degeneracy is generically broken at the level of linear perturbations, where the modifications induce a peculiar scale-dependent pattern. A similar pattern is expected in models of coupled dark energy. I present the main results published in Pogosian and Silvestri [L. Pogosian and A. Silvestri, Phys. Rev. D 77, 023503 (2008) [arXiv:0709.0296 [astro-ph]], on the growth of structure in f(R) theories of gravity, and in Zhao et al. [G.B. Zhao, L. Pogosian, A. Silvestri and J. Zylberberg, arXiv:0809.3791 [astro-ph]], on the potential of upcoming and future tomographic surveys to detect departures from the growth of cosmic structure expected within General Relativity with a cosmological constant.