Quintessence and the Separation of Cosmic Microwave Background Peaks

Doran, Michael; Lilley, Matthew; Schwindt, Jan; Wetterich, C.

doi:10.1086/322253

Cited by 126 publications

(184 citation statements)

References 20 publications

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“…However the information we will obtain will be very limited because even the highest redshift points in those sets explore only relatively recent epochs, and therefore the present supernovae data alone are not able to discriminate between the different models (although larger future supernovae catalogues are expected to improve in an important way the present constraints). Accordingly we should rely on complementary information in order to distinguish quintessence models from a cosmological constant or other alternatives [21,22]. Thus for instance, in the particular case of quintessence, dark energy is generated by a scalar field, and there exists the possibility of having density or velocity perturbations which could affect CMB anisotropies [23].…”

Section: Introductionmentioning

confidence: 99%

Confronting quintessence models with recent high-redshift supernovae data

Barro

Maroto

2006

Phys. Rev. D

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We confront the predictions of different quintessence models with recent measurements of the luminosity distance from two sets of supernovae type Ia. In particular, we consider the 157 SNe Ia in the Gold dataset with z < 1:7, and the more recent data containing 71 supernovae obtained by the Supernova Legacy Survey (SNLS) with z < 1. We numerically solve the evolution equations for the Ratra-Peebles inverse power-law model, the double exponential and the hyperbolic cosine quintessence models. We obtain confidence regions from the two datasets in the M ÿ and M ÿ w planes for the different models and compare their predictions with dark energy models with constant equation of state.

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Section: Introductionmentioning

confidence: 99%

Confronting quintessence models with recent high-redshift supernovae data

Barro

Maroto

2006

Phys. Rev. D

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“…One of the features of this model is the variation of equation of state during the expansion of the universe. Various Quintessence models like k-essence [10], tachyonic matter [11], Phantom [12,13] and Chaplygin gas [14] provide various equations of states for the dark energy [13,14,15,16,17,18,19,20,21].…”

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confidence: 99%

Observational Constraints with Recent Data on the DGP Modified Gravity

2008

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We study one of the simplest covariant modified-gravity models based on the Dvali-Gabadadze-Porrati (DGP) brane cosmology, a self-accelerating universe. In this model gravitational leakage into extra dimensions is responsible of late-time acceleration. We mainly focus on the effects of the model parameters on the geometry and the age of universe. Also we investigate the evolution of matter density perturbations in the modified gravity model, and obtain an analytical expression for the growth index, f . We show that increasing Ωr c leads to less growth of the density contrast δ, and also decreases the growth index. We give a fitting formula for the growth index at the present time and indicate that dominant term in this expression verifies the well-known approximation relation f ≃ Ω γ m . As the observational test, the new Supernova Type Ia (SNIa) Gold sample and Supernova Legacy Survey (SNLS) data, size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), the position of the acoustic peak from the CMB observations and the Cluster Baryon Gas Mass Fraction (gas) are used to constrain the parameters of the DGP model. We also combine previous results with large scale structure formation (LSS) from the 2dFGRS survey. Finally to check the consistency of the DGP model, we compare the age of old cosmological objects with age of universe in this model.

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“…X p represents the value of X at the present time and from (18) we can find X p in terms of X 0 . On the other hand substituting X p = g(X 0 ) in (19) we will have direct relation between X 0 and Ω m . So knowing X 0 from observation one can calculate also Ω m .…”

Section: Modified Gravity Models In Palatinimentioning

confidence: 99%

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confidence: 99%

Consistency off(R)=R2−R02gravity with cosmological observations in the Palatini formalism

2007

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In this work we study the dynamics of universe in f (R) = R 2 − R 2 0 modified gravity with Palatini formalism. We use data from recent observations as Supernova Type Ia (SNIa) Gold sample and Supernova Legacy Survey (SNLS) data, size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), the position of the acoustic peak from the CMB observations and large scale structure formation (LSS) from the 2dFGRS survey to put constraint on the parameters of the model. To check the consistency of this action, we compare the age of old cosmological objects with the age of universe. In the combined analysis with the all the observations, we find the parameters of model as R0 = 6.192 [1,2]. Analysis of SNIa and the Cosmic Microwave Background radiation (CMB) observations indicates that about 70% of the total energy of the Universe is made by the dark energy and the rest of it is in the form of dark matter with a few percent of Baryonic matter [3][4][5]. The "cosmological constant" is a possible explanation of the present dynamics of the universe [6]. This term in Einstein field equations can be regarded as a fluid with the equation of state of w = −1. However, there are two problems with the cosmological constant, namely the fine-tuning and the cosmic coincidence. In the framework of quantum field theory, the vacuum expectation value is 123 order of magnitude larger than the observed value of 10 −47 GeV 4 . The absence of a fundamental mechanism which sets the cosmological constant to zero or to a very small value is the cosmological constant problem. The second problem known as the cosmic coincidence, states that why are the energy densities of dark energy and dark matter nearly equal today?There are various solutions for this problem as the decaying cosmological constant models. A non-dissipative minimally coupled scalar field, so-called Quintessence can play the role of this time varying cosmological constant [7][8][9]. The ratio of energy density of this field to the matter density in this model increases by the expansion of the universe and after a while dark energy becomes the dominant term of the energy-momentum tensor. Another approach dealing with this problem is using the modified gravity by changing the Einstein-Hilbert action. Recently a great attention has been devoted to this era because of the prediction of early and late time accelerations in these models [22]. While it seems that the modified gravity and dark energy models are completely different approaches to explain cosmic acceleration, it is possible to unify them in one formalism [23].In this work we obtain the dynamics of the modified gravity f (R) = R 2 − R 2 0 in the Palatini formalism [24] and use the cosmological observations as SNIa, SDSS acoustic peck in CMB and structure formation to put constraint on the parameter of the action. In Sec. II we derive the dynamics of Hubble parameter and scale factor in Palatini formalism for general case of f (R) gravity. In Sec. III using action f (R) = R 2 − R 2 0 we obtain the dynamics of univers...

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Quintessence and the Separation of Cosmic Microwave Background Peaks

Cited by 126 publications

References 20 publications

Confronting quintessence models with recent high-redshift supernovae data

Confronting quintessence models with recent high-redshift supernovae data

Observational Constraints with Recent Data on the DGP Modified Gravity

Consistency off(R)=R2−R02gravity with cosmological observations in the Palatini formalism

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