Transition redshift: new constraints from parametric and nonparametric methods

Rani, N. Sandhya; Jain, Deepak; Mahajan, Shivani; Mukherjee, Avijit; Pires, N.

doi:10.1088/1475-7516/2015/12/045

Cited by 38 publications

(22 citation statements)

References 118 publications

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“…Busca et al (2013) gave a value of 0.82 ±0.08. Blake et al (2012) found z trans ≈ 0.7, the same value is also supported by Sutherland & Rothnie (2015) and by Rani et al (2015). The best fit by Vitenti & Penna-Lima (2015) supports a transition redshift z trans ≈ 0.65.…”

Section: The Transition Redshift From Braking To Accelerationsupporting

confidence: 70%

An Alternative to the Λcdm Model: The Case of Scale Invariance

Maeder

2017

ApJ

159

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The hypothesis is made that, at large scales where General Relativity may be applied, the empty space is scale invariant. This establishes a relation between the cosmological constant and the scale factor λ of the scale invariant framework. This relation brings major simplifications in the scale invariant equations for cosmology, which contain a new term, depending on the derivative of the scale factor, that opposes to gravity and produces an accelerated expansion. The displacements due to the acceleration term make a high contribution Ω λ to the energy-density of the Universe, satisfying an equation of the form Ω m + Ω k + Ω λ = 1. The models do not demand the existence of unknown particles. There is a family of flat models with different density parameters Ω m < 1. Numerical integrations of the cosmological equations for different values of the curvature and density parameter k and Ω m are performed. The presence of even tiny amounts of matter in the Universe tends to kill scale invariance. The point is that for Ω m = 0.3 the effect is not yet completely killed. The models with non-zero density start explosively with first a braking phase followed by a continuously accelerating expansion. Several observational properties are examined, in particular the distances, the m-z diagram, the Ω m vs. Ω λ plot. Comparisons with observations are also performed for the Hubble constant H 0 vs. Ω m , for the expansion history in the plot H(z)/(z + 1) vs. redshift z and for the transition redshift from braking to acceleration. These first dynamical tests are satisfied by the scale invariant models, which thus deserve further studies.

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Section: The Transition Redshift From Braking To Accelerationsupporting

confidence: 70%

An Alternative to the Λcdm Model: The Case of Scale Invariance

Maeder

2017

ApJ

159

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“…Recently, also ref. [75] analysed the age of galaxies, strong lensing and SNe obtaining a constraint on z t < 1, considering both a parametric and a non-parametric approach. Note that previous results were obtained from the analysis of SNe, comprising SNLS and Union2 samples, BAO and from the latest CMB measurements from Planck satellite, while in our case the measurement comes only from cosmic chronometers data and the local H(z) measurement.…”

Section: The Measurement Of the Transition Redshiftmentioning

confidence: 99%

A 6% measurement of the Hubble parameter at z∼0.45: direct evidence of the epoch of cosmic re-acceleration

Moresco

Pozzetti

Cimatti

et al. 2016

J. Cosmol. Astropart. Phys.

920

610

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Deriving the expansion history of the Universe is a major goal of modern cosmology. To date, the most accurate measurements have been obtained with Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO), providing evidence for the existence of a transition epoch at which the expansion rate changes from decelerated to accelerated. However, these results have been obtained within the framework of specific cosmological models that must be implicitly or explicitly assumed in the measurement. It is therefore crucial to obtain measurements of the accelerated expansion of the Universe independently of assumptions on cosmological models. Here we exploit the unprecedented statistics provided by the Baryon Oscillation Spectroscopic Survey (BOSS, [1, 2, 3]) Data Release 9 to provide new constraints on the Hubble parameter H(z) using the cosmic chronometers approach. We extract a sample of more than 130000 of the most massive and passively evolving galaxies, obtaining five new cosmology-independent H(z) measurements in the redshift range 0.3 < z < 0.5, with an accuracy of ∼11-16% incorporating both statistical and systematic errors. Once combined, these measurements yield a 6% accuracy constraint of H(z = 0.4293) = 91.8 ± 5.3 km/s/Mpc. The new data are crucial to provide the first cosmology-independent determination of the transition redshift at high statistical significance, measuring z t = 0.4 ± 0.1, and to significantly disfavor the null hypothesis of no transition between decelerated and accelerated expansion at 99.9% confidence level. This analysis highlights the wide potential of the cosmic chronometers approach: it permits to derive constraints on the expansion history of the Universe with results competitive with standard probes, and most importantly, being the estimates independent of the cosmological model, it can constrain cosmologies beyondand including -the ΛCDM model.

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“…Recent studies reveals that the present observed deceleration rate of the Universe is q 0 = −0.51 +0.09 −0.01 [41] and a transition redshift from deceleration to acceleration is z t = 0.65 +0.19 −0.17 [42]. In literature [43][44][45] reported that the Universe passed from a decelerated phase to an accelerated one at z t ≈ 0.7 [46] . So, we have chosen the values of these free parameters (k 1 , k 2 , k 3 , k 4 ) in the present model in such way that our q 0 and z t result are consistent with values reported in the literature.…”

Section: General Solutionmentioning

confidence: 98%

Effective equation of state in modified gravity and observational constraints

Arora

Meng

Pacif

et al. 2020

Class. Quantum Grav.

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In this article, the bulk viscosity is introduced in a modified gravity model. The gravitational action has a general f (R, T) form, where R and T are the curvature scalar and the trace of energy momentum tensor respectively. An effective equation of state (EoS) has been investigated in the cosmological evolution with bulk viscosity. In the present scenario, the Hubble parameter which has a scaling relation with the redshift can be obtained generically. The role of deceleration parameter q and equation of state parameter ω is discussed to explain the late-time accelerating expansion of the universe. The statefinder parameters and Om diagnostic analysis are discussed for our obtained model to distinguish from other dark energy models together with the analysis of energy conditions and velocity of sound for the model. We have also numerically investigated the model by detailed maximum likelihood analysis of 580 Type Ia supernovae from Union 2.1 compilation datasets and updated 57 Hubble datasets (31 data points from differential age method and 26 points from BAO and other methods). It is with efforts found that the present model is in good agreement with observations.

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Transition redshift: new constraints from parametric and nonparametric methods

Cited by 38 publications

References 118 publications

An Alternative to the Λcdm Model: The Case of Scale Invariance

An Alternative to the Λcdm Model: The Case of Scale Invariance

A 6% measurement of the Hubble parameter at z∼0.45: direct evidence of the epoch of cosmic re-acceleration

Effective equation of state in modified gravity and observational constraints

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