Abebe, AmareAbdelwahab, MohamedCruz Dombriz, Álvaro de laDunsby, Peter K. S.2023-06-202023-06-202012-07-070264-938110.1088/0264-9381/29/13/135011https://hdl.handle.net/20.500.14352/44480© 2012 IOP Publishing Ltd. The authors thank the National Research Foundation (NRF, SouthAfrica) for financial support. AdlCD also acknowledges financial support from MICINN (Spain) project numbers FPA 2008-00592, FIS 2011-23000 and Consolider-Ingenio MULTIDARK CSD2009-00064.We study the evolution of scalar cosmological perturbations in the 1 + 3 covariant gauge-invariant formalism for generic f(R) theories of gravity. Extending previous works, we give a complete set of equations describing the evolution of matter and curvature fluctuations for a multi-fluid cosmological medium. We then specialize to a radiation-dust fluid described by barotropic equations of state and solve the perturbation equations around a background solution of R^n gravity. In particular, we study exact solutions for scales much smaller and much larger than the Hubble radius and show that n > 2/3 in order to have a growth rate compatible with the Mészáros effect.engjournal articlehttp://dx.doi.org/10.1088/0264-9381/29/13/135011http://arxiv.org/abs/1110.1191http://iopscience.iop.org/open access53Probe wmap observationsCosmological perturbationsDark energyConstantDynamicsModelsFísica (Física)22 Física