@article{oai:nagoya.repo.nii.ac.jp:00009494,
 author = {Cognola, G. and Elizalde, E. and Nojiri, S. and Odintsov, S. D. and Sebastiani, L. and Zerbini, S.},
 issue = {4},
 journal = {PHYSICAL REVIEW D},
 month = {Feb},
 note = {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-step 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, nonviolation of Newton's law, and generation of a very heavy positive mass for the additional scalar degree of freedom.},
 pages = {046009--046009},
 title = {Class of viable modified f(R) gravities describing inflation and the onset of accelerated expansion},
 volume = {77},
 year = {2008}
}