Scalar-Tensor Dark Energy Models

Gannouji, Radouane; Polarski, David; André, Ranquet; Starobinsky, A. A.

doi:10.1142/9789812834300_0259

Cited by 12 publications

(11 citation statements)

References 8 publications

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“…In this class of models, the parameter w(z) can also be defined from equation (1.6) but it can not be interpreted as pX ρX of a perfect fluid. The simplest (but quite general) examples of modified gravity theories are scalar tensor theories [24,30,31,32,33] where the Newton's constant G is promoted to a function of a field Φ: 8πG → 1 F (Φ) whose dynamics at the Lagrangian level is determined by a potential U (Φ). Assuming homogeneity and isotropy, the modified Friedman equation in these theories take the form…”

Section: Introductionmentioning

confidence: 99%

Crossing the phantom divide: theoretical implications and observational status

Nesseris

Perivolaropoulos

2007

J. Cosmol. Astropart. Phys.

340

292

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If the dark energy equation of state parameter w(z) crosses the phantom divide line w = −1 (or equivalently if the expression2 changes sign) at recent redshifts, then there are two possible cosmological implications: Either the dark energy consists of multiple components with at least one non-canonical phantom component or general relativity needs to be extended to a more general theory on cosmological scales. The former possibility requires the existence of a phantom component which has been shown to suffer from serious theoretical problems and instabilities. Therefore, the latter possibility is the simplest realistic theoretical framework in which such a crossing can be realized. After providing a pedagogical description of various dark energy observational probes, we use a set of such probes (including the Gold SnIa sample, the first year SNLS dataset, the 3-year WMAP CMB shift parameter, the SDSS baryon acoustic oscillations peak (BAO), the X-ray gas mass fraction in clusters and the linear growth rate of perturbations at z = 0.15 as obtained from the 2dF galaxy redshift survey) to investigate the priors required for cosmological observations to favor crossing of the phantom divide. We find that a low Ω0m prior (0.2 < Ω0m < 0.25) leads, for most observational probes (except of the SNLS data), to an increased probability (mild trend) for phantom divide crossing. An interesting degeneracy of the ISW effect in the CMB perturbation spectrum is also pointed out.

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Section: Introductionmentioning

confidence: 99%

Crossing the phantom divide: theoretical implications and observational status

Nesseris

Perivolaropoulos

2007

J. Cosmol. Astropart. Phys.

340

292

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“…The main assumption of this theory is a connection between the matter and the scalar and gravitationalˇelds ϕ and g μν via some effective metricsg μν = A 2 (ϕ)g μν . In the paper [70], a scalarÄtensor model of dark energy with a new degree of physical freedom has been considered. It is argued that the scalarˇeld ϕ of graviton is responsible for the change of gravitational one.…”

Section: Model With Interaction Between Dark Energy and Dark Mattermentioning

confidence: 99%

Isotropic and anisotropic dark energy models

Saha

2014

Phys. Part. Nuclei

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The evolution of the Universeˇlled with dark energy (DE) with or without perfect uid is discussed. In doing so, we consider a number of cosmological models, namely Bianchi type I, III, V, VI 0 , VI, and FRW one. For the anisotropic cosmological models we have used proportionality condition as an additional constraint. The exact solutions to theˇeld equations in quadrature are found in the case of a BVI model. It was found that the proportionality condition used here imposed severe restriction on the energyÄmomentum tensor, namely, it leads to isotropic distribution of matter.Anisotropic BVI 0 , BV, BIII, and BI DE models with variable EoS parameter ω have been investigated by using a law of variation for the Hubble parameter. In this case the matter distribution remains anisotropic, though, depending on the concrete model, there appear different restrictions on the components of energyÄmomentum tensor. That is why we need an extra assumption such as a variational law for the Hubble parameter. It is observed that, at the early stage, the EoS parameter ω is positive, i.e., the Universe was matter-dominated at the early stage but at later time the Universe is evolving with negative values, i.e., the present epoch. DE model presents the dynamics of EoS parameter ω whose range is in good agreement with the acceptable range by the recent observations.A spatially homogeneous and anisotropic locally rotationally symmetric Bianchi-I spaceÄtimě lled with perfect uid and anisotropic DE possessing dynamical energy density is studied. In the derived model, the EoS parameter of DE (ω (de) ) is obtained as time varying and it is evolving with negative sign which may be attributed to the current accelerated expansion of Universe. The distance modulus curve of derived model is in good agreement with SNLS type Ia supernovae for high red-shift value which in turn implies that the derived model is physically realistic.A system of two uids within the scope of a spatially at and isotropic FRW model is studied. The role of the two uids, either minimally or directly coupled in the evolution of the dark energy parameter, has been investigated. In doing so, we have used three different ansatzs regarding the scale factor that gives rise to a variable decelerating parameter. It is observed that, in the noninteracting case, both the open and the at Universes can cross the phantom region whereas in the interacting case only the open Universe can cross the phantom region. The stability and acceptability of the obtained solution are also investigated.

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“…So far, many models have been proposed to fit the observations including cosmological constant (Weinberg 1989;Sahni and Starobinsky 2000;Carroll 2001;Peebles and Ratra 2003;Padmanabhan 2003), quintessence (Amendola et al 2006a;Elizalde et al 2004;Nojiri et al 2004;Nojiri and Odintsov 2006;Boisseau et al 2000;Esposito-Farese and Polarski 2001;Zhang 2005b;Setare 2006;Faraoni and Jensen 2006;Wetterich 1988;Copeland et al 2006;Ferreira and Joyce 1998;Frieman et al 1995;Brax and Martin 2000;Barreiro et al 2000;Zlatev et al 1999;Padmanabhan and Choudhury 2002;Sen 2002b;Armendariz-Picon et al 1999;Feinstein 2002;Fairbairn and Tytgat 2002;Frolov et al 2002;Kofman and Linde 2004;Acatrinei and Sochichiu 2003;Alexander 2002;Mazumadar et al 2001;Sarangi and Tye 2002;Huang et al 2007a;Huang et al 2007b;Fang et al 2007), phantom (Amendola et al 2006b;Amendola 2004;Gannouji et al 2006;Lu 2005;…”

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confidence: 99%

Statefinder diagnostic for dilaton dark energy

Huang

Song

et al. 2008

Astrophys Space Sci

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Statefinder diagnostic is a useful method which can differ one dark energy model from the others. The Statefinder pair {r, s} is algebraically related to the equation of state of dark energy and its first time derivative. We apply in this paper this method to the dilaton dark energy model based on Weyl-Scaled induced gravitational theory. We investigate the effect of the coupling between matter and dilaton when the potential of dilaton field is taken as the Mexican hat form. We find that the evolving trajectory of our model in the r − s diagram is quite different from those of other dark energy models.

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Scalar-Tensor Dark Energy Models

Cited by 12 publications

References 8 publications

Crossing the phantom divide: theoretical implications and observational status

Crossing the phantom divide: theoretical implications and observational status

Isotropic and anisotropic dark energy models

Statefinder diagnostic for dilaton dark energy

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