Cosmological Constraints from Low-Redshift Data

Luković, Vladimir V.; Haridasu, Balakrishna S.; Vittorio, N.

doi:10.1007/s10701-018-0202-z

Cited by 17 publications

(11 citation statements)

References 260 publications

(334 reference statements)

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“…This now-standard model assumes flat spatial geometry, with cold dark matter (CDM) being the second-largest E-mail: hisourav@gmail.com (∼ 26%; Planck Collaboration 2018) contributor to the current energy budget. The standard ΛCDM model is consistent with many current observational constraints (for reviews of Λ and ΛCDM see Ratra & Vogeley 2008;Martin 2012;Luković et al 2018, and references therein). However, current data cannot rule out slightly curved spatial hypersurfaces or mild dark energy dynamics.…”

Section: Introductionsupporting

confidence: 69%

First study of reionization in tilted flat and untilted non-flat dynamical dark energy inflation models

Mitra¹,

Park

Choudhury

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We examine the effects of dark energy dynamics and spatial curvature on cosmic reionization by studying reionization in tilted spatially-flat and untilted non-flat XCDM and φCDM dynamical dark energy inflation models that best fit the Planck 2015 cosmic microwave background (CMB) anisotropy and a large compilation of non-CMB data. We carry out a detailed statistical study, based on a principal component analysis and a Markov chain Monte Carlo analysis of a compilation of lower-redshift reionization data, to estimate the uncertainties in the cosmological model reionization histories. We find that, irrespective of the nature of dark energy, there are significant differences between the reionization histories of the spatially-flat and non-flat models. Although both the flat and non-flat models can accurately match the low-redshift (z 6) reionization observations, there is a clear discrepancy between high-redshift (z > 7) Lyman-α emitter data and the predictions from non-flat models. This is solely due to the fact that the non-flat models have a significantly larger electron scattering optical depth, τ el , compared to the flat models, which requires an extended and much earlier reionization scenario supported by more high-redshift ionizing sources in the non-flat models. Non-flat models also require strong redshift evolution in the photon escape fraction, that can become unrealistically high ( 1) at some redshifts. However, τ el is about 0.9-σ lower in the tilted flat ΛCDM model when the new Planck 2018 data are used and this reduction will partially alleviate the tension between the non-flat model predictions and the data.

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Section: Introductionsupporting

confidence: 69%

First study of reionization in tilted flat and untilted non-flat dynamical dark energy inflation models

Mitra¹,

Park

Choudhury

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…1, thus bringing the z = 0 prediction of the CMB closer to the H 0 result of the local measurements of Ref. [32] • Inhomogeneous cosmologies [51] that would make a local deep underdensity more likely than in the case of ΛCDM.…”

Section: Introductionmentioning

confidence: 74%

Is gravity getting weaker at low z? Observational evidence and theoretical implications

Kazantzidis,

Perivolaropoulos

2019

Preprint

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Dynamical observational probes of the growth of density perturbations indicate that gravity may be getting weaker at low redshifts z. This evidence is at about 2 − 3σ level and comes mainly from weak lensing data that measure the parameter S8 = σ8 Ω0m/0.3 and redshift space distortion data that measure the growth rate times the amplitude of the linear power spectrum parameter f σ 8 (z). The measured f σ 8 appears to be lower than the prediction of General Relativity (GR) in the context of the standard ΛCDM model as defined by the Planck best fit parameter values. This is the well known f σ 8 tension of ΛCDM, which constitutes one of the two main large scale challenges of the model along with the H0 tension. We review the observational evidence that leads to the f σ 8 tension and discuss some theoretical implications. If this tension is not a systematic effect it may be an early hint of modified gravity with an evolving effective Newton's constant G ef f and gravitational slip parameter η. We discuss such best fit parametrizations of G eff (z) and point out that they can not be reproduced by simple scalar-tensor and f (R) modified gravity theories because these theories generically predict stronger gravity than General Relativity (GR) at low z in the context of a ΛCDM background H(z). Finally, we show weak evidence for an evolving reduced absolute magnitude of the SnIa of the Pantheon dataset at low redshifts (z < 0.1) which may also be explained by a reduced strength of gravity and may help resolve the H0 tension.

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“…It is worth noting here that a tension seems to persist between the local measurement values and the lower value obtained from Planck, i.e., H 0 = 66.93 ± 0.62 km s −1 Mpc −1 . This tension has been the subject of numerous discussions in recent literature offering different perspectives (Bernal et al 2016;Lin and Ishak 2017b,a;Luković et al 2018;Wang et al 2017;Haridasu et al 2017;Zhang et al 2018;Gómez-Valent and Amendola 2018;Abbott et al 2017b). As we discuss further below in some of the sub-sections (see e.g., Sect.…”

Section: Local Measurements Of the Hubble Constant Or Measurements Of...mentioning

confidence: 88%

Testing general relativity in cosmology

2018

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We review recent developments and results in testing general relativity (GR) at cosmological scales. The subject has witnessed rapid growth during the last two decades with the aim of addressing the question of cosmic acceleration and the dark energy associated with it. However, with the advent of precision cosmology, it has also become a well-motivated endeavor by itself to test gravitational physics at cosmic scales. We overview cosmological probes of gravity, formalisms and parameterizations for testing deviations from GR at cosmological scales, selected modified gravity (MG) theories, gravitational screening mechanisms, and computer codes developed for these tests. We then provide summaries of recent cosmological constraints on MG parameters and selected MG models. We supplement these cosmological constraints with a summary of implications from the recent binary neutron star merger event. Next, we summarize some results on MG parameter forecasts with and without astrophysical systematics that will dominate the uncertainties. The review aims at providing an overall picture of the subject and an entry point to students and researchers interested in joining the field. It can also serve as a quick reference to recent results and constraints on testing gravity at cosmological scales.

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Cosmological Constraints from Low-Redshift Data

Abstract: In this paper we summarise the constraints that low-redshift data -such as supernovae Ia (SN Ia), baryon acoustic oscillations (BAO) and cosmic chronometers (CC)are able to set on the concordance model and its extensions,

Cited by 17 publications

References 260 publications

First study of reionization in tilted flat and untilted non-flat dynamical dark energy inflation models

First study of reionization in tilted flat and untilted non-flat dynamical dark energy inflation models

Is gravity getting weaker at low z? Observational evidence and theoretical implications

Testing general relativity in cosmology

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