Backreaction mechanism in multifluid and extended cosmologies

摘要: One possible explanation for the present observed acceleration of Universe is breakdown homogeneity and isotropy due to formation non-linear structures. How inhomogeneities affect averaged cosmological expansion rate lead late-time generally considered be some backreaction mechanism. General Relativity together with pressure-free matter have until recently been as sole ingredients calculations. In this communication we focus our attention on more general scenarios, including imperfect fluids well alternative theories gravity, apply an averaging procedure them in order determine effects. For illustrative purposes, results dark energy models, quintessence Brans-Dicke theories. We also provide a discussion about limitations frame choices procedure.