We search for viable f(R) theories of gravity, making use of the equivalence between such theories and scalar-tensor gravity. We find that models can be made consistent with solar system constraints either by giving the scalar a high mass or by exploiting the so-called chameleon effect. However, in both cases, it appears likely that any late-time cosmic acceleration will be observationally indistinguishable from acceleration caused by a cosmological constant. We also explore further observational constraints from, e.g., big bang nucleosynthesis and inflation.

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Copyright © 2007 The American Physical Society. This article first appeared in Physical Review D 76, no. 6 (September 13, 2007): 063505-1-63505-17. doi:10.1103/PhysRevD.76.063505

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