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arXiv · 0712.4017

Class of viable modified $f(R)$ gravities describing inflation and the onset of accelerated expansion

G. Cognola·E. Elizalde·S. Nojiri·S. D. Odintsov·L. Sebastiani·S. Zerbini
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Abstract

A general approach to viable modified $f(R)$ gravity is developed in both the Jordan and the Einstein frames. A class of exponential, realistic modified gravities is introduced and investigated with care. Special focus is made on step-class models, most promising from the phenomenological viewpoint and which provide a natural way to classify all viable modified gravities. One- and two-steps models are explicitly considered, but the analysis is extensible to $N$-step models. Both inflation in the early universe and the onset of recent accelerated expansion arise in these models in a natural, unified way. Moreover, it is demonstrated that models in this category easily pass all local tests, including stability of spherical body solution, non-violation of Newton's law, and generation of a very heavy positive mass for the additional scalar degree of freedom.

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G. Cognola, E. Elizalde, S. Nojiri, S. D. Odintsov, L. Sebastiani, S. Zerbini. 2008-01-30. Class of viable modified $f(R)$ gravities describing inflation and the onset of accelerated expansion. https://doi.org/10.1103/physrevd.77.046009

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