Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-07-19
New J.Phys.8:323,2006
Astronomy and Astrophysics
Astrophysics
22 pages, 6 figures, uses iopart style
Scientific paper
10.1088/1367-2630/8/12/323
One way to account for the acceleration of the universe is to modify general relativity, rather than introducing dark energy. Typically, such modifications introduce new degrees of freedom. It is interesting to consider models with no new degrees of freedom, but with a modified dependence on the conventional energy-momentum tensor; the Palatini formulation of $f(R)$ theories is one example. Such theories offer an interesting testing ground for investigations of cosmological modified gravity. In this paper we study the evolution of structure in these ``modified-source gravity'' theories. In the linear regime, density perturbations exhibit scale dependent runaway growth at late times and, in particular, a mode of a given wavenumber goes nonlinear at a higher redshift than in the standard $\Lambda$CDM model. We discuss the implications of this behavior and why there are reasons to expect that the growth will be cut off in the nonlinear regime. Assuming that this holds in a full nonlinear analysis, we briefly describe how upcoming measurements may probe the differences between the modified theory and the standard $\Lambda$CDM model.
Carroll Sean M.
Sawicki Ignacy
Silvestri Alessandra
Trodden Mark
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