scholarly journals Constraints on $$\sigma _8$$ and degeneracies from linear Nash-Greene perturbations in subhorizon scale

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Abraão J. S. Capistrano
Keyword(s):  
Large Scale ◽  
Present Model ◽  
Information Criterion ◽  
Matter Content ◽  
Data Sets ◽  
Acoustic Oscillations ◽  
Growth Data ◽  
Microwave Background ◽  
Percentage Difference ◽  
Type Ia

AbstractUsing a joint statistical analysis, we test a four-dimensional FLRW model embedded in a five-dimensional bulk based on the Nash-Greene embedding theorem. Performing a Markov Chain Monte Carlo (MCMC) modelling, we combine observational data sets as those of the recent growth data, the best-fit Planck2018/$$\varLambda $$ Λ CDM parameters on the Cosmic Microwave Background (CMB), the Baryon Acoustic Oscillations (BAO) measurements, the Pantheon Supernovae type Ia and the Hubble parameter data. From linear Nash-Greene fluctuations of the metric, we show the related perturbed equations in longitudinal Newtonian gauge to obtain the evolution of growth matter. A mild alleviation may be obtained from the degeneracies on the model parameter analyzing the $$\sigma $$ σ tension between the growth amplitude factor and the matter content in the plane $$(\sigma _8$$ ( σ 8 -$$\varOmega _m)$$ Ω m ) on the observations from CMB and Large Scale Structure (LSS) probes. The Akaike Information Criterion (AIC) is also applied and we find a relative statistical consistence of the present model with both $$\varLambda $$ Λ CDM and wCDM models lower than 1$$\%$$ % of percentage difference at early times on the evolution of the Hubble function H(z). We also apply the Om(z) diagnosis to distinguish the present model from $$\varLambda $$ Λ CDM and wCDM models.

scholarly journals THE ΛCDM GROWTH RATE OF STRUCTURE REVISITED

2012 ◽  
Vol 21 (07) ◽  
pp. 1250064 ◽  
Author(s):  
SPYROS BASILAKOS
Keyword(s):  
Growth Rate ◽  
Growth Index ◽  
Acoustic Oscillations ◽  
Growth Data ◽  
Microwave Background ◽  
Shift Parameter ◽  
Likelihood Analysis ◽  
Type Ia ◽  
Supernovae Type Ia ◽  
Baryonic Acoustic Oscillations

We re-examine the growth index of the concordance Λ cosmology in the light of the latest 6dF and WiggleZ data. In particular, we investigate five different models for the growth index γ, by comparing their cosmological evolution using observational data of the growth rate of structure formation at different redshifts. Performing a joint likelihood analysis of the recent supernovae type Ia data, the Cosmic Microwave Background shift parameter, Baryonic Acoustic Oscillations and the growth rate data, we determine the free parameters of the γ(z) parametrizations and we statistically quantify their ability to represent the observations. We find that the addition of the 6dF and WiggleZ growth data in the likelihood analysis improves significantly the statistical results. As an example, considering a constant growth index we find Ωm0 = 0.273 ± 0.011 and [Formula: see text].

scholarly journals Sub-horizon modes and growth index in a linear scalar cosmological perturbations

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Abraão J. S. Capistrano
Keyword(s):  
Growth Index ◽  
Information Criterion ◽  
Relative Difference ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Statistical Equivalence ◽  
Proposed Model ◽  
Type Ia ◽  
Temperature Spectra ◽  
Growth Profiles

AbstractWe test a four dimensional cosmological model embedded in a five dimensional bulk space by means of the dynamical Nash-Greene theorem. In a fluid approach, we apply a joint likelihood analysis to the data with the Markov Chain Monte Carlo (MCMC) method for cosmological parameter estimation. We use recent datasets as the “Gold 2018” growth-rate data, the Planck2018/$$\varLambda $$ Λ CDM data on the cosmic microwave background (CMB) anisotropies, the Baryon acoustic oscillations (BAO) measurements, the Pantheon Supernovae type Ia and the data on the Hubble parameter H(z) with redshift ranging from $$0.01< z < 2.3$$ 0.01 < z < 2.3 . Performing the Information Criterion (IC) analysis, we find that the present model is in very good agreement with observations with a close statistical equivalence with wCDM cosmologies at 1-$$\sigma $$ σ level with a slightly larger growth profiles. By modifications of () code, we make a comparison between the models on their unlensed CMB TT temperature spectra. Moreover, the proposed model presents a low power spectrum by the reduction of the ISW effect at lower multipoles. We also find that the overall percentage relative difference of the growth index $$\varDelta \gamma (\%)$$ Δ γ ( % ) is up to 1.4$$\%$$ % as compared to wCDM pattern in sub-horizon scales.

Cosmological constraints on the variable modified Chaplygin gas model by using MCMC approach

2015 ◽  
Vol 24 (08) ◽  
pp. 1550059 ◽  
Author(s):  
Jian-bin Chen ◽  
Zhen-qi Liu ◽  
Lili Xing
Keyword(s):  
Apparent Horizon ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Mean Values ◽  
Cosmological Constraints ◽  
Variable Modified Chaplygin Gas ◽  
Type Ia ◽  
Ia Supernovae

We investigate the cosmological constraints on the variable modified Chaplygin gas (VMCG) model from the latest observational data: Union2 dataset of Type Ia supernovae (SNIa), the observational Hubble data (OHD), the baryon acoustic oscillations (BAO) and the cosmic microwave background (CMB) data. By using the Markov chain Monte Carlo (MCMC) method, we obtain the mean values of parameters in the flat model: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. Furthermore, we investigate the thermodynamical properties of VMCG model at apparent horizon, event horizon and particle horizon respectively.

scholarly journals Cosmology from large-scale structure

2020 ◽  
Vol 633 ◽  
pp. L10 ◽  
Author(s):  
Tilman Tröster ◽  
Ariel. G. Sánchez ◽  
Marika Asgari ◽  
Chris Blake ◽  
Martín Crocce ◽  
...  
Keyword(s):  
Cosmic Microwave Background ◽  
Parameter Space ◽  
Large Scale ◽  
Bayes Factor ◽  
Large Scale Structure ◽  
Data Sets ◽  
Microwave Background ◽  
Shape Information ◽  
Galaxy Clustering ◽  
Cosmological Constraints

We reanalyse the anisotropic galaxy clustering measurement from the Baryon Oscillation Spectroscopic Survey (BOSS), demonstrating that using the full shape information provides cosmological constraints that are comparable to other low-redshift probes. We find Ωm = 0.317+0.015−0.019, σ8 = 0.710±0.049, and h = 0.704 ± 0.024 for flat ΛCDM cosmologies using uninformative priors on Ωch2, 100θMC, ln1010As, and ns, and a prior on Ωbh2 that is much wider than current constraints. We quantify the agreement between the Planck 2018 constraints from the cosmic microwave background and BOSS, finding the two data sets to be consistent within a flat ΛCDM cosmology using the Bayes factor as well as the prior-insensitive suspiciousness statistic. Combining two low-redshift probes, we jointly analyse the clustering of BOSS galaxies with weak lensing measurements from the Kilo-Degree Survey (KV450). The combination of BOSS and KV450 improves the measurement by up to 45%, constraining σ8 = 0.702 ± 0.029 and S8 = σ8 Ωm/0.3 = 0.728 ± 0.026. Over the full 5D parameter space, the odds in favour of a single cosmology describing galaxy clustering, lensing, and the cosmic microwave background are 7 ± 2. The suspiciousness statistic signals a 2.1 ± 0.3σ tension between the combined low-redshift probes and measurements from the cosmic microwave background.

The Large Scale Structure Peak as a Comoving Standard Ruler

2005 ◽  
Vol 201 ◽  
pp. 388-391
Author(s):  
Boudewijn F. Roukema ◽  
Gary A. Mamon
Keyword(s):  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Data Sets ◽  
Density Parameter ◽  
Observable Universe ◽  
Standard Candle ◽  
Type Ia ◽  
Density Perturbations ◽  
Empirical Standard

Estimates of the curvature parameters Ω0 (density parameter) and Δ0 (cosmological constant) can be made geometrically by use of either a standard candle or a standard ruler. Just as supernovae of Type Ia appear to provide a good empirical standard candle, it now appears observationally justified to use the peak in the power spectrum of density perturbations at L ≍ 130±10h-1 Mpc as an empirical standard rod. It will be shown that voids of this size are traced by quasars in a homogeneous catalogue near the South Galactic Pole at z ˜ 2 and that the large scale structure peak of the catalogue constrains the value of Ω0 to 0.1 < Ω0 < 0.45 (68% confidence), independently of Δ0. Combination with the supernovae Ia data is sufficient to show that the observable Universe is almost flat. In other words, the combination of a standard ruler and a standard candle detected in two presently available data sets is sufficient to show that the Universe is nearly flat, independently of any microwave background data or any other data analyses.

scholarly journals A divergence-free parametrization of deceleration parameter for scalar field dark energy

2016 ◽  
Vol 25 (03) ◽  
pp. 1650032 ◽  
Author(s):  
Abdulla Al Mamon ◽  
Sudipta Das
Keyword(s):  
Dark Energy ◽  
Deceleration Parameter ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Frw Universe ◽  
Potential Term ◽  
Type Ia ◽  
De Formula ◽  
Divergence Free ◽  
Baryonic Acoustic Oscillations

In this paper, we have considered a spatially flat FRW universe filled with pressureless matter and dark energy (DE). We have considered a phenomenological parametrization of the deceleration parameter [Formula: see text] and from this, we have reconstructed the equation-of-state (EoS) for DE [Formula: see text]. This divergence-free parametrization of the deceleration parameter is inspired from one of the most popular parametrization of the DE EoS given by Barboza and Alcaniz [see E. M. Barboza and J. S. Alcaniz, Phys. Lett. B 666 (2008) 415]. Using the combination of datasets (Type Ia Supernova (SN Ia) + Hubble + baryonic acoustic oscillations/cosmic microwave background (BAO/CMB)), we have constrained the transition redshift [Formula: see text] (at which the universe switches from a decelerating to an accelerating phase) and have found the best fit value of [Formula: see text]. We have also compared the reconstructed results of [Formula: see text] and [Formula: see text] and have found that the results are compatible with a [Formula: see text]CDM universe if we consider SN Ia + Hubble data, but inclusion of BAO/CMB data makes [Formula: see text] and [Formula: see text] incompatible with [Formula: see text]CDM model. The potential term for the present toy model is found to be functionally similar to a Higgs potential.

scholarly journals Can f(R) gravity relieve $$H_0$$ and $$\sigma _8$$ tensions?

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Deng Wang
Keyword(s):  
Cosmic Microwave Background ◽  
Confidence Level ◽  
Cosmological Parameters ◽  
Type Ia Supernovae ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Type Ia ◽  
Baryon Acoustic Oscillations ◽  
Ia Supernovae

AbstractTo investigate whether f(R) gravity can relieve current $$H_0$$ H 0 and $$\sigma _8$$ σ 8 tensions, we constrain the Hu-Sawicki f(R) gravity with Planck-2018 cosmic microwave background and redshift space distortions observations. We find that this model fails to relieve both $$H_0$$ H 0 and $$\sigma _8$$ σ 8 tensions, and that its two typical parameters $$\log _{10}f_{R0}$$ log 10 f R 0 and n are insensitive to other cosmological parameters. Combining the cosmic microwave background, baryon acoustic oscillations, Type Ia supernovae, cosmic chronometers with redshift space distortions observations, we give our best constraint $$\log _{10}f_{R0}<-6.75$$ log 10 f R 0 < - 6.75 at the $$2\sigma $$ 2 σ confidence level.

scholarly journals Large Scale Structure Among z ∼ 2 Quasars as a Cosmological Standard Ruler

2002 ◽  
Vol 199 ◽  
pp. 54-55 ◽  
Author(s):  
B.F. Roukema ◽  
G.A. Mamon
Keyword(s):  
Power Spectrum ◽  
Cosmological Constant ◽  
Confidence Limit ◽  
Large Scale ◽  
Density Parameter ◽  
Confidence Limits ◽  
Microwave Background ◽  
Type Ia ◽  
Supernovae Type Ia ◽  
Quasar Distribution

The peak in the power spectrum at ≈ 130h−1 Mpc at low redshifts provides a standard ruler in comoving space. This scale is shown to be present in the observed quasar distribution at z ∼ 2. This implies strong constraints on the density parameter, Ω0, and weaker constraints on the cosmological constant, λ0. Independently of λ0 (in the range λ0 ∊ [0, 1]), the constraint is 0.1 < Ω0 < 0.45 (68% confidence limit).Combination of the power spectrum peak method with very independent results from the supernovae Type Ia method yields Ω0 = (0.30 ± 0.11) + (0.57 ± 0.11)(λ0 −0.7), 0.55 < λ0 < 0.95, (68% confidence limits) without assuming Ω0 + λ0 = 1. This supports the almost flat, perturbed Friedmann-Lemaître-Robertson-Walker model, independently of any cosmic microwave background observations.

scholarly journals OBSERVATIONAL CONSTRAINTS ON PHANTOM CROSSING DGP GRAVITY

2011 ◽  
Vol 20 (01) ◽  
pp. 1-16 ◽  
Author(s):  
KOICHI HIRANO ◽  
ZEN KOMIYA
Keyword(s):  
Observational Constraints ◽  
Late Time ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Phantom Divide ◽  
Phantom Crossing ◽  
Type Ia ◽  
Acceleration Of The Universe ◽  
Ia Supernovae ◽  
Best Fit

We study the observational constraints on the Phantom Crossing DGP model. We demonstrate that the crossing of the phantom divide does not occur within the framework of the original Dvali–Gabadadze–Porrati (DGP) model or the DGP model developed by Dvali and Turner. By extending their model in the framework of an extra dimension scenario, we study a model that realizes crossing of the phantom divide. We investigate the cosmological constraints obtained from the recent observational data of Type Ia supernovae, cosmic microwave background anisotropies, and baryon acoustic oscillations. The best-fit values of the parameters with 1σ (68%) errors for the Phantom Crossing DGP model are [Formula: see text]. We find that the Phantom Crossing DGP model is more compatible with the observations than the original DGP model or the DGP model developed by Dvali and Turner. Our model can realize late-time acceleration of the universe, similar to that of ΛCDM model, without dark energy due to the effect of DGP gravity. In our model, the crossing of the phantom divide occurs at a redshift of z ~ 0.2.

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