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.

Statistics of Cosmic Microwave Background Radiation with the Cosmic String Model

1997 ◽  
Vol 06 (05) ◽  
pp. 535-544
Author(s):  
Petri Mähönen ◽  
Tetsuya Hara ◽  
Toivo Voll ◽  
Shigeru Miyoshi
Keyword(s):  
Cosmic Microwave Background ◽  
Cosmic String ◽  
Large Scale ◽  
Background Radiation ◽  
Unit Length ◽  
Angular Size ◽  
Cosmic Microwave Background Radiation ◽  
Density Parameter ◽  
Microwave Background ◽  
Microwave Background Radiation

We have studied the cosmic microwave background radiation by simulating the cosmic string network induced anisotropies on the sky. The large-angular size simulations are based on the Kaiser–Stebbins effect calculated from full cosmic-string network simulation. The small-angular size simulations are done by Monte-Carlo simulation of perturbations from a time-discretized toy model. We use these results to find the normalization of μ, the string mass per unit length, and compare this result with one needed for large-scale structure formation. We show that the cosmic string scenario is in good agreement with COBE, SK94, and MSAM94 microwave background radiation experiments with reasonable string network parameters. The predicted rms-temperature fluctuations for SK94 and MSAM94 experiments are Δ T/T=1.57×10-5 and Δ T/T=1.62×10-5, respectively, when the string mass density parameter is chosen to be Gμ=1.4×10-6. The possibility of detecting non-Gaussian signals using the present day experiments is also discussed.

scholarly journals NATURAL INFLATION, PLANCK SCALE PHYSICS AND OSCILLATING PRIMORDIAL SPECTRUM

2005 ◽  
Vol 14 (08) ◽  
pp. 1347-1364 ◽  
Author(s):  
XIULIAN WANG ◽  
BO FENG ◽  
MINGZHE LI ◽  
XUE-LEI CHEN ◽  
XINMIN ZHANG
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
High Frequency ◽  
Large Scale ◽  
Planck Scale ◽  
Microwave Background ◽  
Precision Data ◽  
Inflation Model ◽  
High Precision Data ◽  
Planck Scale Physics

In the "natural inflation" model, the inflaton potential is periodic. We show that Planck scale physics may induce corrections to the inflaton potential, which is also periodic with a greater frequency. Such high frequency corrections produce oscillating features in the primordial fluctuation power spectrum, which are not entirely excluded by the current observations and may be detectable in high precision data of cosmic microwave background (CMB) anisotropy and large scale structure (LSS) observations.

scholarly journals The Hubble constant from eight time-delay galaxy lenses

2020 ◽  
Vol 501 (1) ◽  
pp. 784-801 ◽  
Author(s):  
Philipp Denzel ◽  
Jonathan P Coles ◽  
Prasenjit Saha ◽  
Liliya L R Williams
Keyword(s):  
Time Delay ◽  
Hubble Constant ◽  
Free Form ◽  
Microwave Background ◽  
Form Analysis ◽  
Systematic Uncertainties ◽  
Type Ia ◽  
Modelling Strategies ◽  
Supernovae Type Ia

ABSTRACT We present a determination of the Hubble constant from the joint, free-form analysis of eight strongly, quadruply lensing systems. In the concordance cosmology, we find $H_0{} = 71.8^{+3.9}_{-3.3}\, \mathrm{km}\, \mathrm{s}^{-1}\, \mathrm{Mpc}^{-1}{}{}$ with a precision of $4.97{{\ \rm per\ cent}}$. This is in agreement with the latest measurements from supernovae Type Ia and Planck observations of the cosmic microwave background. Our precision is lower compared to these and other recent time-delay cosmography determinations, because our modelling strategies reflect the systematic uncertainties of lensing degeneracies. We furthermore are able to find reasonable lensed image reconstructions by constraining to either value of H0 from local and early Universe measurements. This leads us to conclude that current lensing constraints on H0 are not strong enough to break the ‘Hubble tension’ problem of cosmology.

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 Exact joint likelihood of pseudo-Cℓ estimates from correlated Gaussian cosmological fields

2019 ◽  
Vol 491 (3) ◽  
pp. 3165-3181 ◽  
Author(s):  
Robin E Upham ◽  
Lee Whittaker ◽  
Michael L Brown
Keyword(s):  
Quadratic Form ◽  
Power Spectrum ◽  
Quadratic Forms ◽  
Joint Distribution ◽  
Large Scale ◽  
Power Spectra ◽  
Microwave Background ◽  
Cosmological Constraints ◽  
Statistical Precision ◽  
Joint Likelihood

ABSTRACT We present the exact joint likelihood of pseudo-Cℓ power spectrum estimates measured from an arbitrary number of Gaussian cosmological fields. Our method is applicable to both spin-0 fields and spin-2 fields, including a mixture of the two, and is relevant to cosmic microwave background (CMB), weak lensing, and galaxy clustering analyses. We show that Gaussian cosmological fields are mixed by a mask in such a way that retains their Gaussianity and derive exact expressions for the covariance of the cut-sky spherical harmonic coefficients, the pseudo-aℓms, without making any assumptions about the mask geometry. We then show that each auto or cross-pseudo-Cℓ estimator can be written as a quadratic form, and apply the known joint distribution of quadratic forms to obtain the exact joint likelihood of a set of pseudo-Cℓ estimates in the presence of an arbitrary mask. We show that the same formalism can be applied to obtain the exact joint likelihood of quadratic maximum likelihood power spectrum estimates. Considering the polarization of the CMB as an example, we show using simulations that our likelihood recovers the full, exact multivariate distribution of EE, BB, and EB pseudo-Cℓ power spectra. Our method provides a route to robust cosmological constraints from future CMB and large-scale structure surveys in an era of ever-increasing statistical precision.

scholarly journals Reconstructing the Primordial Power Spectrum

2005 ◽  
Vol 216 ◽  
pp. 28-34
Author(s):  
S. L. Bridle ◽  
A. M. Lewis ◽  
J. Weller ◽  
G. Efstathiou
Keyword(s):  
Power Spectrum ◽  
Spectral Index ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Microwave Background ◽  
Primordial Power Spectrum ◽  
Initial Spectrum ◽  
Redshift Survey ◽  
Cosmic Microwave Background Data

We reconstruct the shape of the primordial power spectrum from the latest cosmic microwave background data, including the new results from the Wilkinson Microwave Anisotropy Probe (WMAP), and large scale structure data from the two degree field galaxy redshift survey (2dFGRS). We discuss two parameterizations taking into account the uncertainties in four cosmological parameters. First we parameterize the initial spectrum by a tilt and a running spectral index, finding marginal evidence for a running spectral index only if the first three WMAP multipoles (ℓ = 2, 3, 4) are included in the analysis. Secondly, to investigate further the low CMB large scale power, we modify the conventional power-law spectrum by introducing a scale above which there is no power. We find a preferred position of the cut at kc ∼ 3 × 10--4 Mpc--1 although kc = 0 (no cut) is not ruled out.

scholarly journals BRANE UNIVERSES TESTED AGAINST ASTRONOMICAL DATA

2004 ◽  
Vol 13 (08) ◽  
pp. 1669-1702 ◽  
Author(s):  
MARIUSZ P. DABROWSKI ◽  
WŁODZIMIERZ GODŁOWSKI ◽  
MAREK SZYDŁOWSKI
Keyword(s):  
Cosmological Constant ◽  
Likelihood Method ◽  
Model Parameters ◽  
Density Parameter ◽  
Brane Model ◽  
Fitting Procedure ◽  
Type Ia ◽  
The Difference ◽  
Age Of The Universe ◽  
Phantom Matter

We discuss observational constrains coming from supernovae imposed on the behaviour of the Randall–Sundrum models. We test the models using the Perlmutter SNIa data as well as the new Knop and Tonry/Barris samples. The data indicates that, under the assumption that we admit zero pressure dust matter on the brane, the cosmological constant is still needed to explain current observations. We estimate the model parameters using the best-fitting procedure and the likelihood method. The observations from supernovae give a large value of the density parameter for brane matter Ωλ,0≃0.01 as the best fit. For high redshifts z>1.2, the difference between the brane model and the ΛCDM (Perlmutter) model becomes detectable observationally. From the maximum likelihood method we obtained the favored value of Ωλ,0=0.004±0.016 for Ωk,0=0 and Ω m ,0=0.3. This gives the limit Ωλ,0<0.02 at 1σ level. While the model with brane effects is preferred by the supernovae type Ia data, the model without brane fluid is still statistically admissible. We also discuss how fit depends on restrictions of the sample, especially with respect to redshift criteria. We also pointed out the property of sensitive dependence of results with respect to the choice of ℳ parameter. For comparison the limit on brane effects which comes from CMB anisotropies and BBN is also obtained. The uncertainty in the location of the first peak gives a stronger limit Ωλ,0<1.0×10-12, whereas from BBN we obtain that Ωλ,0<1.0×10-27. However, both very strict limits are obtained with the assumption that brane effects do not change the physics in the pre-recombination era, while the SNIa limit is model independent. We demonstrate that the fit to supernovae data can also be obtained if we admit the phantom matter p=-(4/3)ϱ on the brane, where this matter mimics the influence of the cosmological constant. We show that phantom matter enlarges the age of the universe on the brane which is demanded in cosmology. Finally, we propose to check for dark radiation and brane tension by the application of the angular diameter of galaxies minimum value test.

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.

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