2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/187695We 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.15 pages, 5 figuresAstrophysicsGeneral Relativity and Quantum Cosmologytext