Effective growth of matter density fluctuations in the running Λ CDM and Λ XCDM models

Grande, Javier; Opher, R.; Pelinson, Ana; Solà, Joan

doi:10.1088/1475-7516/2007/12/007

Cited by 33 publications

(53 citation statements)

References 54 publications

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“…[11], dark energy perturbations can be neglected in the ΛðtÞCDM model. This is justified in most cases [11,66]. Similarly, it is assumed that perturbations in the α 4 H 2 0 terms are negligible in the present model.…”

Section: Density Perturbations In the Modified Entropic-force Modelmentioning

confidence: 85%

Entropic cosmology in a dissipative universe

Komatsu

2014

Phys. Rev. D

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The bulk viscosity of cosmological fluid and the creation of cold dark matter both result in the generation of irreversible entropy (related to dissipative processes) in a homogeneous and isotropic universe. To consider such effects, the general cosmological equations are reformulated, focusing on a spatially flat matter-dominated universe. A phenomenological entropic-force model is examined that includes constant terms as a function of the dissipation rate ranging fromμ ¼ 0, corresponding to a nondissipative ΛCDM (lambda cold dark matter) model, toμ ¼ 1, corresponding to a fully dissipative CCDM (creation of cold dark matter) model. A time-evolution equation is derived for the matter density contrast in order to characterize density perturbations in the present entropic-force model. It is found that the dissipation rate affects the density perturbations even if the background evolution of the late universe is equivalent to that of a fine-tuned pure ΛCDM model. With increasing dissipation rateμ, the calculated growth rate for the clustering gradually deviates from observations, especially at low redshifts. However, the growth rate for lowμ (less than 0.1) is found to agree well with measurements. A low-dissipation model predicts a smaller growth rate than does the pure ΛCDM model (for whichμ ¼ 0). More detailed data are needed to distinguish the low-dissipation model from the pure ΛCDM one.

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Section: Density Perturbations In the Modified Entropic-force Modelmentioning

confidence: 85%

Entropic cosmology in a dissipative universe

Komatsu

2014

Phys. Rev. D

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“…[6], since it is based on the effective action due to quantum effects in the universe. A variation of such a model is the so-called ÃXCDM model [5], where the cosmological term is supposed to interact with a new field, called cosmon, which has an equation of state p X ¼ ! X X .…”

Section: The Modelmentioning

confidence: 99%

“…In Ref. [5] the ÃXCDM model has been studied using also the growth of linear perturbations, and restrictions on the parameter space of the model were obtained. But the cosmological term was considered as smooth: the authors At the center, the PDF distribution of the dark energy density parameter when the cosmological term is not perturbed is shown and at the right the same for the case when the cosmological term is perturbed.…”

Section: The Mass Power Spectrummentioning

confidence: 99%

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Evolution of density perturbations in decaying vacuum cosmology: The case of nonzero perturbations in the cosmological term

Borges

Carneiro²,

Fabris³

2008

Phys. Rev. D

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We extend the results of a previous paper where a model of interacting dark energy, with a cosmological term decaying linearly with the Hubble parameter, is tested against the observed mass power spectrum. In spite of the agreement with observations of type Ia supernovas, baryonic acoustic oscillations, and the cosmic microwave background, we had shown previously that no good concordance is achieved if we include the mass power spectrum. However, our analysis was based on the ad hoc assumption that the interacting cosmological term is strictly homogeneous. Now we perform a more complete analysis, by perturbing such a term. Although our conclusions are still based on a particular, scale-invariant choice of the primordial spectrum of dark energy perturbations, we show that a cosmological term decaying linearly with the Hubble parameter is indeed disfavored as compared to the standard model.

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“…(10) implies that dark energy perturbations are assumed to be negligible. This assumption is generally justified in most cases [12,73] and has been most recently examined in the work of Gómez-Valent and Solà [17]. In this study, we assume that boundary perturbations are negligible in holographic cosmological models [60].…”

Section: Formulations For the λ(T) Modelmentioning

confidence: 95%

Evolution of dissipative and non-dissipative universes in holographic cosmological models with a power-law term

Komatsu

2020

Preprint

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Density perturbations related to structure formations are expected to be different in dissipative and non-dissipative universes, even if the background evolution of the two universes is the same. To clarify the difference between the two universes, first-order density perturbations are studied, using two types of holographic cosmological models. The first type is a "Λ(t) model" similar to a time-varying Λ(t) cosmology for the non-dissipative universe. The second type is a "BV model" similar to a bulk viscous cosmology for the dissipative universe. To systematically examine the two different universes, a power-law term proportional to H α is applied to the Λ(t) and BV (bulk-viscouscosmology-like) models, assuming a flat Friedmann-Robertson-Walker model for the late universe.Here, H is the Hubble parameter and α is a free parameter whose value is a real number. The Λ(t)-H α and BV-H α models are used to examine first-order density perturbations for matter, in which the background evolution of the two models is equivalent. In addition, thermodynamic constraints on the two models are discussed, with a focus on the maximization of entropy on the horizon of the universe, extending previous analyses [Phys. Rev. D 100, 123545 (2019); 102, 63512 (2020)]. Consequently, the Λ(t)-H α model for small |α| values is found to be consistent with observations and satisfies the thermodynamic constraints, compared with the BV-H α model. The results show that the non-dissipative universe described by the Λ(t)-H α model similar to lambda cold dark matter models is likely favored.

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Effective growth of matter density fluctuations in the running Λ CDM and Λ XCDM models

Cited by 33 publications

References 54 publications

Entropic cosmology in a dissipative universe

Entropic cosmology in a dissipative universe

Evolution of density perturbations in decaying vacuum cosmology: The case of nonzero perturbations in the cosmological term

Evolution of dissipative and non-dissipative universes in holographic cosmological models with a power-law term

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