2007
DOI: 10.1088/1475-7516/2007/12/005
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Expansion history andf(R) modified gravity

Abstract: We attempt to fit cosmological data using f (R) modified Lagrangians containing inverse powers of the Ricci scalar varied with respect to the metric. While we can fit the supernova data well, we confirm the a ∝ t 1/2 behaviour at medium to high redshifts reported elsewhere and argue that the easiest way to show that this class of models are inconsistent with the data is by considering the thickness of the last scattering surface. For the best fit parameters to the supernova data, the simplest 1/R model gives r… Show more

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Cited by 27 publications
(19 citation statements)
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“…However, this model suffers from a number of problems such as matter instability [215, 244], the instability of cosmological perturbations [146, 74, 544, 526, 251], the absence of the matter era [28, 29, 239], and the inability to satisfy local gravity constraints [469, 470, 245, 233, 154, 448, 134]. The main reason why this model does not work is that the quantity f , RR ≡ ∂ 2 f/ ≡ R 2 is negative.…”
Section: Dark Energy In F(r) Theoriesmentioning
confidence: 99%
“…However, this model suffers from a number of problems such as matter instability [215, 244], the instability of cosmological perturbations [146, 74, 544, 526, 251], the absence of the matter era [28, 29, 239], and the inability to satisfy local gravity constraints [469, 470, 245, 233, 154, 448, 134]. The main reason why this model does not work is that the quantity f , RR ≡ ∂ 2 f/ ≡ R 2 is negative.…”
Section: Dark Energy In F(r) Theoriesmentioning
confidence: 99%
“…In particular, the observational viability of some functional forms of f (R) gravity have been studied using mainly SNe Ia, CMB radiation and Large Scale Structure (LSS) data [41,54,42,43].…”
Section: Introductionmentioning
confidence: 99%
“…However, several quantum-gravity theories postulate that familiar concepts such as Lorentz invariance may be broken at energies approaching the Planck energy scale, E P ∼ 1.2×10 19 GeV (e.g., Amelino et al 1998;Jacob & Piran 2008;Liberati & Maccione 2009;Amelino 2013;Tavecchio & Bonnoli 2016). Currently such extreme energies are unreachable by experiments on Earth, but for photons traveling over cosmological distances the accumulated deviations from Lorentz invariance may be measurable using Imaging Atmospheric Cherenkov Telescope facilities, in particular the future Cherenkov Telescope Array (CTA) (e.g., Fairbairn et al 2014;Lorentz & Brun 2017).…”
Section: Introductionmentioning
confidence: 99%