High Energy Physics - Theory
[Submitted on 31 Oct 2008 (v1), last revised 31 Mar 2009 (this version, v2)]
Title:Construction of cosmologically viable f(G) gravity models
View PDFAbstract: We derive conditions under which f(G) gravity models, whose Lagrangian densities f are written in terms of a Gauss-Bonnet term G, are cosmologically viable. The most crucial condition to be satisfied is that f_GG, the second derivative of f with respect to G, must be positive, which is required to ensure the stability of a late-time de-Sitter solution as well as the existence of standard radiation/matter dominated epochs. We present a number of explicit f(G) models in which a cosmic acceleration is followed by the matter era. We find that the equation of state of dark energy can cross the phantom divide before reaching the present Universe. The viable models have asymptotic behavior f_GG goes to +0 when |G| goes to infinity, in which case a rapid oscillation of perturbations occurs unless such an oscillating degree of freedom is suppressed relative to a homogeneous mode in the early universe. We also introduce an iterative method to avoid numerical instabilities associated with a large mass of the oscillating mode.
Submission history
From: Antonio De Felice [view email][v1] Fri, 31 Oct 2008 15:22:49 UTC (213 KB)
[v2] Tue, 31 Mar 2009 07:01:22 UTC (214 KB)
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