Linear coasting in cosmology and SNe Ia

Dev, Abha; Sethi, Meetu; Lohiya, Daksh

doi:10.1016/s0370-2693(01)00292-1

Cited by 42 publications

(61 citation statements)

References 14 publications

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“…A coasting expansion seems to provide the best fit of the recent observations of supernovas and radio sources [22]. Furthermore, it leads to a universe age given by Ht = 1, once again in good accordance with the observational limits [23].…”

Section: Discussionsupporting

confidence: 80%

“…As discussed in [22], among the solutions of the form a ∝ t n , the best fitting of supernova and radio sources observations is obtained in the coasting case, a ∝ t. On the other hand, the relation Ht = 1 gives the best estimation for the universe age [23], and the relative matter density given by (22) matches surprisingly well the observed value [24].…”

Section: Decaying λ Solutionsmentioning

confidence: 68%

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Time Dependent Cosmological Term and Holography

Carneiro

Lima

2005

Int. J. Mod. Phys. A

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We discuss a class of uniform and isotropic, spatially flat, decaying Λ cosmologies, in the realm of a model where the gravitation "constant" G is a function of the cosmological time. Besides the usual de Sitter solution, the models at late times are characterized by a constant ratio between the matter and total energy densities. One of them presents a coasting expansion where the matter density parameter is Ωm = 1/3, and the age of the universe satisfies Ht = 1. From considerations in line with the holographic conjecture, it is argued that, among the non-decelerating solutions, the coasting expansion is the only acceptable from a thermodynamic viewpoint, and that the time varying cosmological term must be proportional to H 2 , a result earlier obtained using different arguments.

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Section: Discussionsupporting

confidence: 80%

Section: Decaying λ Solutionsmentioning

confidence: 68%

Time Dependent Cosmological Term and Holography

Carneiro

Lima

2005

Int. J. Mod. Phys. A

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“…This is in accordance with the result of Dev et al (2001). Our analysis, therefore, provides an independent and complementary test of this class of model.…”

Section: Final Remarkssupporting

confidence: 90%

Testing power-law cosmology with galaxy clusters

Zhu

Hu²,

Alcaniz

et al. 2008

A&A

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Aims. Power-law cosmologies, in which the cosmological scale factor evolves as a power law in time, a ∝ t α with α > ∼ 1, regardless of the matter content or cosmological epoch, is comfortably concordant with a host of cosmological observations. Methods. In this article, we use recent measurements of the X-ray gas mass fractions in clusters of galaxies to constrain the α parameter with curvature k = ±1, 0. Results. We find that the best fit happens for an open scenario with the power index α = 1.14 ± 0.05, though the flat and closed model cannot be ruled out with high confidence. Conclusions. Our results are in agreement with other recent analyses and show that the X-ray gas mass fraction measurements in clusters of galaxies provide a complementary test of the power-law cosmology.

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“…In fact such high quality q 0 = 0 fits (viz. fits with R(t) = (−k) 1/2 ct) have already been reported earlier, [19] with the authors of [2] having noted in passing that such fits were actually as good as their best standard model fits, and with the authors of [20] having presented such q 0 = 0 fits in an exploration of generic power law expansion rate cosmologies. What is new here is that we derive such q 0 = 0 fits within the framework of a well-defined cosmological model while also extending them to non-zero q 0 (i.e.…”

Section: Fits To the Hubble Plotsupporting

confidence: 55%

How Recent Is Cosmic Acceleration?

Mannheim

2003

Int. J. Mod. Phys. D

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Possibly the most peculiar expectation of the standard fine-tuned cosmological paradigm is that cosmic acceleration is to only be a very recent (z < 1) phenomenon, with the universe being required to be decelerating at all higher redshifts. Detailed exploration of the Hubble plot out to z = 2 or so will not only provide an absolute test of this expectation but will also allow for testing of conformal gravity, a non fine-tuned alternate cosmological theory which provides equally good fitting to the current z < 1 Hubble plot data while requiring the universe to be accelerating at higher z instead. With both standard and conformal gravity being found to be compatible with a very recently reported z = 1.7 data point, additional data points will thus be needed to determine whether the universe is accelerating or decelerating above z = 1. I. THE HUBBLE PLOT OF STANDARD COSMOLOGYA variety of recent observational measurements [1][2][3][4] have sharply constrained the space available to the standard model cosmological parameters. Specifically, phenomenological data fitting using the standard Einstein-Friedmann cosmological evolution equatioṅ(where Ω M (t) = 8πGρ M (t)/3c 2 H 2 (t) is due to ordinary ρ M (t) ∼ 1/R n (t) matter and where Ω Λ (t) = 8πGΛ/3cH 2 (t) is due to a cosmological constant cΛ) is found to favor current era values Ω M (t 0 ) ≃ 0.3 and Ω Λ (t 0 ) ≃ 0.7, with the current era deceleration parameter q 0 = q(t 0 ) = (n/2 − 1)Ω M (t 0 ) − Ω Λ (t 0 ) then having to be of order −1/2. While these values are very supportive of the flat Ω k (t) = −kc 2 /Ṙ 2 (t) = 1 − Ω M (t) − Ω Λ (t) = 0 inflationary universe paradigm [5], they are nonetheless extremely troubling. Specifically, solving Eq. (1) for ρ M (t) = B/R 3 (t) and k = 0 yields R(t) = (B/cΛ) 1/3 sinh 2/3 (3D 1/2 t/2) where D = 8πGΛ/3c, so that Ω Λ (t) = D/H 2 (t) = 1 − Ω M (t) = tanh 2 (3D 1/2 t/2).(2) *

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Linear coasting in cosmology and SNe Ia

Cited by 42 publications

References 14 publications

Time Dependent Cosmological Term and Holography

Time Dependent Cosmological Term and Holography

Testing power-law cosmology with galaxy clusters

How Recent Is Cosmic Acceleration?

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