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Isotropic and anisotropic bouncing cosmologies in Palatini gravity

AuthorsOlmo, Gonzalo J. ; Barragán, Carlos
Issue Date11-Oct-2010
PublisherAmerican Physical Society
CitationPhysical Review - Section D - Particles and Fields 82 (8): 084015 (2010)
AbstractWe study isotropic and anisotropic (Bianchi I) cosmologies in Palatini f(R) and f(R, R mu nu R mu nu) theories of gravity with a perfect fluid and consider the existence of nonsingular bouncing solutions in the early universe. We find that all f(R) models with isotropic bouncing solutions develop shear singularities in the anisotropic case. On the contrary, the simple quadratic model R + aR(2)/R-P + R mu nu R mu nu/R-P exhibits regular bouncing solutions in both isotropic and anisotropic cases for a wide range of equations of state, including dust (for a<0) and radiation (for arbitrary a). It thus represents a purely gravitational solution to the big bang singularity and anisotropy problems of general relativity without the need for exotic (w>1) sources of matter/energy or extra degrees of freedom.
Publisher version (URL)http://dx.doi.org/10.1103/PhysRevD.82.084015
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