Decaying Λ cosmologies and power spectrum

Silveira, Vanda; Waga, I.

doi:10.1103/physrevd.50.4890

Cited by 179 publications

(176 citation statements)

References 23 publications

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“…Useful expressions of the growth factor can be found for the ΛCDM cosmology in [60], for dark energy models with w = const in [63], [22], [25], [64], for dark energy models with a time varying equation of state in [65] and for the scalar tensor models in [66]. Finally, in this work, the growth factor evolution for the current cosmological model is derived by solving numerically eq.…”

Section: A the Evolution Of The Linear Growth Factormentioning

confidence: 99%

Spherical collapse model and cluster formation beyond theΛcosmology: Indications for a clustered dark energy?

2009

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We generalize the small scale dynamics of the universe by taking into account models with an equation of state which evolves with time, and provide a complete formulation of the cluster virialization attempting to address the nonlinear regime of structure formation. In the context of the current dark energy models, we find that galaxy clusters appear to form at z ∼ 1 − 2, in agreement with previous studies. Also, we investigate thoroughly the evolution of spherical matter perturbations, as the latter decouple from the background expansion and start to "turn around" and finally collapse. Within this framework, we find that the concentration parameter depends on the choice of the considered dark energy (homogeneous or clustered). In particular, if the distribution of the dark energy is clustered then we produce more concentrated structures with respect to the homogeneous dark energy. Finally, comparing the predicted concentration parameter with the observed concentration parameter, measured for four massive galaxy clusters, we find that the scenario which contains a pure homogeneous dark energy is unable to reproduce the data. The situation becomes somewhat better in the case of an inhomogeneous (clustered) dark energy.PACS numbers: 98.80.-k, 95.35.+d, 95.36.+x

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Section: A the Evolution Of The Linear Growth Factormentioning

confidence: 99%

Spherical collapse model and cluster formation beyond theΛcosmology: Indications for a clustered dark energy?

2009

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“…For ΛCDM the growing mode can be expressed in terms of hypergeometric function 2 F 1 as (Silveira & Waga 1994) …”

Section: γ Gravity Reviewmentioning

confidence: 99%

N-body simulations ofγgravity

Santos

Winther

Mota

et al. 2016

A&A

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We have investigated structure formation in the γ gravity f (R) model with N-body simulations. The γ gravity model is a proposal which, unlike other viable f (R) models, not only changes the gravitational dynamics, but can in principle also have signatures at the background level that are different from those obtained in ΛCDM (Cosmological constant, Cold Dark Matter). The aim of this paper is to study the nonlinear regime of the model in the case where, at late times, the background differs from ΛCDM. We quantify the signatures produced on the power spectrum, the halo mass function, and the density and velocity profiles. To appreciate the features of the model, we have compared it to ΛCDM and the Hu-Sawicki f (R) models. For the considered set of parameters we find that the screening mechanism is ineffective, which gives rise to deviations in the halo mass function that disagree with observations. This does not rule out the model per se, but requires choices of parameters such that | f R0 | is much smaller, which would imply that its cosmic expansion history cannot be distinguished from ΛCDM at the background level.

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“…(3.11) for a flat GR model with a constant dark energy equation of state w is given for the growing mode by [31][32][33]:…”

Section: The Growth Rate Of Density Perturbationsmentioning

confidence: 99%

A new perspective on dark energy modeling via genetic algorithms

Nesseris¹,

García-Bellido²

2012

J. Cosmol. Astropart. Phys.

118

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We use Genetic Algorithms to extract information from several cosmological probes, such as the type Ia supernovae (SnIa), the Baryon Acoustic Oscillations (BAO) and the growth rate of matter perturbations. This is done by implementing a model independent and bias-free reconstruction of the various scales and distances that characterize the data, like the luminosity dL(z) and the angular diameter distance dA(z) in the SnIa and BAO data, respectively, or the dependence with redshift of the matter density Ωm(a) in the growth rate data, f σ8(z). These quantities can then be used to reconstruct the expansion history of the Universe, and the resulting Dark Energy (DE) equation of state w(z) in the context of FRW models, or the mass radial function ΩM (r) in LTB models. In this way, the reconstruction is completely independent of our prior bias. Furthermore, we use this method to test the Etherington relation, ie the well-known relation between the luminosity and the, which is equal to 1 in metric theories of gravity. We find that the present data seem to suggest a 3-σ deviation from one at redshifts z ∼ 0.5. Finally, we present a novel way, within the Genetic Algorithm paradigm, to analytically estimate the errors on the reconstructed quantities by calculating a Path Integral over all possible functions that may contribute to the likelihood. We show that this can be done regardless of the data being correlated or uncorrelated with each other and we also explicitly demonstrate that our approach is in good agreement with other error estimation techniques like the Fisher Matrix approach and the Bootstrap Monte Carlo.

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Decaying Λ cosmologies and power spectrum

Cited by 179 publications

References 23 publications

Spherical collapse model and cluster formation beyond theΛcosmology: Indications for a clustered dark energy?

Spherical collapse model and cluster formation beyond theΛcosmology: Indications for a clustered dark energy?

N-body simulations ofγgravity

A new perspective on dark energy modeling via genetic algorithms

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