Testing Einstein’s gravity and dark energy with growth of matter perturbations: Indications for new physics?

We perform an Internal Robustness analysis (iR) to a compilation of the most recent f σ8(z) data, using the framework of Ref. [1]. The method analyzes combinations of subsets in the data set in a Bayesian model comparison way, potentially finding outliers, subsets of data affected by systematics or new physics. In order to validate our analysis and assess its sensitivity we performed several cross-checks, for example by removing some of the data or by adding artificially contaminated points, while we also generated mock data sets in order to estimate confidence regions of the iR. Applying this methodology, we found no anomalous behavior in the f σ8(z) data set, thus validating its internal robustness. PACS numbers: 95.36.+x, 04.50.Kd, 98.80.Es

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“…To speed up the computations, we note that the σ 8,0 parameter can be marginalized theoretically [24,25]. We rewrite the χ 2 :…”

Section: Formalismmentioning

confidence: 99%

Internal robustness of growth rate data

2018

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“…in Refs. [7,[44][45][46][47][48][49][50][51]. 1 In certain cases we consider the deviation around Ωm =0.3 instead of Ωm =Ω P m (2) The observable f σ 8 (z) has a blind spot with respect to the parameter g a at redshift z 2.7.…”

Section: Growth Of Density Perturbationsmentioning

confidence: 99%

Constraining power of cosmological observables: Blind redshift spots and optimal ranges

2019

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2 − 3σ) is the Ω m − σ 8 tension between the CMB Planck data and the growth of density perturbations data (RSD and WL) [5][6][7][8][9]. The CMB data favor higher values of the matter density parameter Ω m and the matter fluctuations amplitude σ 8 than the data that probe directly the gravitational interaction (RSD and WL).A key question therefore arises: Are these tensions an early hint of new physics beyond the standard model or are they a result of systematic/statistical fluctuations in the data?Completed, ongoing and future CMB experiments and large scale structure surveys aim at testing the standard ΛCDM model and addressing the above question. These surveys are classified in four stages. Stages I and II correspond to completed surveys and CMB experiments, while stages III and IV correspond to ongoing and future projects respectively. For example stage II CMB experiments include WMAP [10], Planck [2, 3], ACTPol [11] and SPT-Pol [12], while stage III CMB experiments include AdvACT [13] and SPT-3G [14]. Future stage IV CMB probes on the ground[15] and in space such as Lite-BIRD [16, 17] mainly aim to measure CMB lensing and the CMB-B modes in detail.A large amount of high-quality data is expected in the coming years from large scale structure surveys (see Table I). Stage III large scale structure surveys include the Canada-France-Hawaii Telescope Lensing Survey [18], the Kilo Degree Survey (KiDS) [8,9], the extended arXiv:1812.05356v2 [astro-ph.CO]

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“…A compilation of 63 f σ 8 measurements published by various surveys from 2006 to present is shown in Table II along with the corresponding fiducial cosmology assumed in each case. Despite of the existence of such a large sample of published f σ 8 data, most previous analyses [27,31,34,56,[58][59][60][61][62][63][64][65][66][67][68] that use growth data to constrain cosmological models use less than 20 data points which are usually selected from the larger data set of Table II on the basis of subjective criteria that favor more recent data as well as a qualitative minimization of correlations among the selected data points. Indeed, since many of these data points are correlated due to overlap in the galaxy samples used for their derivation, a large covariance matrix should be used for their combined analysis.…”

Section: Introductionmentioning

confidence: 99%

Evolution of the fσ8 tension with the Planck15/ΛCDM determination and implications for modified gravity theories

2018

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We construct an updated extended compilation of distinct (but possibly correlated) f σ8(z) redshift space distortion (RSD) data published between 2006 and 2018. It consists of 63 data points and is significantly larger than previously used similar data sets. After fiducial model correction we obtain the best fit Ω0m − σ8 ΛCDM parameters and show that they are at a 5σ tension with the corresponding Planck15/ΛCDM values. Introducing a nontrivial covariance matrix correlating randomly 20% of the RSD data points has no significant effect on the above tension level. We show that the tension disappears (becomes less than 1σ) when a subsample of the 20 most recently published data is used. A partial cause for this reduced tension is the fact that more recent data tend to probe higher redshifts (with higher errorbars) where there is degeneracy among different models due to matter domination. Allowing for a nontrivial evolution of the effective Newton's constant(ga is a parameter) and fixing a Planck15/ΛCDM background we find ga = −0.91 ± 0.17 from the full f σ8 data set while the 20 earliest and 20 latest data points imply ga = −1.28 +0.28 −0.26 and ga = −0.43 +0.46 −0.41 respectively. Thus, the more recent f σ8 data appear to favor GR in contrast to earlier data. Finally, we show that the parametrization f σ8(z) = λσ8Ω(z) γ /(1 + z) β provides an excellent fit to the solution of the growth equation for both GR (ga = 0) and modified gravity (ga = 0).

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Testing Einstein’s gravity and dark energy with growth of matter perturbations: Indications for new physics?

Cited by 43 publications

References 128 publications

Internal robustness of growth rate data

Internal robustness of growth rate data

Constraining power of cosmological observables: Blind redshift spots and optimal ranges

Evolution of the fσ8 tension with the Planck15/ΛCDM determination and implications for modified gravity theories

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