scholarly journals Testing Gaussianity, Homogeneity, and Isotropy with the Cosmic Microwave Background

2010 ◽  
Vol 2010 ◽  
pp. 1-25 ◽  
Author(s):  
L. Raul Abramo ◽  
Thiago S. Pereira
Keyword(s):  
Simple Model ◽  
Cosmic Microwave Background ◽  
Large Scale ◽  
Microwave Background ◽  
Statistical Framework ◽  
Model Independent

We review the basic hypotheses which motivate the statistical framework used to analyze the cosmic microwave background, and how that framework can be enlarged as we relax those hypotheses. In particular, we try to separate as much as possible the questions of gaussianity, homogeneity, and isotropy from each other. We focus both on isotropic estimators of nongaussianity as well as statistically anisotropic estimators of gaussianity, giving particular emphasis on their signatures and the enhanced “cosmic variances” that become increasingly important as our putative Universe becomes less symmetric. After reviewing the formalism behind some simple model-independent tests, we discuss how these tests can be applied to CMB data when searching for large-scale “anomalies”.

scholarly journals Model-Independent Test for Scale-Dependent Non-Gaussianities in the Cosmic Microwave Background

2009 ◽  
Vol 102 (13) ◽  
Author(s):  
C. Räth ◽  
G. E. Morfill ◽  
G. Rossmanith ◽  
A. J. Banday ◽  
K. M. Górski
Keyword(s):  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Independent Test ◽  
Model Independent

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 Inflation physics from the cosmic microwave background and large scale structure

2015 ◽  
Vol 63 ◽  
pp. 55-65 ◽  
Author(s):  
K.N. Abazajian ◽  
K. Arnold ◽  
J. Austermann ◽  
B.A. Benson ◽  
C. Bischoff ◽  
...  
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background

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 Model-independent constraints on the hydrogen-ionizing emissivity at z > 6

2019 ◽  
Vol 489 (2) ◽  
pp. 2669-2676 ◽  
Author(s):  
Charlotte A Mason ◽  
Rohan P Naidu ◽  
Sandro Tacchella ◽  
Joel Leja
Keyword(s):  
Cosmic Microwave Background ◽  
Bayesian Analysis ◽  
Optical Depth ◽  
Total Output ◽  
Rapid Decline ◽  
Parametric Form ◽  
Microwave Background ◽  
Model Independent ◽  
Dark Pixel ◽  
Non Parametric

ABSTRACT Modelling reionization often requires significant assumptions about the properties of ionizing sources. Here, we infer the total output of hydrogen-ionizing photons (the ionizing emissivity, $\dot{N}_\textrm {ion}$) at z = 4–14 from current reionization constraints, being maximally agnostic to the properties of ionizing sources. We use a Bayesian analysis to fit for a non-parametric form of $\dot{N}_\textrm {ion}$, allowing us to flexibly explore the entire prior volume. We infer a declining $\dot{N}_\textrm {ion}$ with redshift at z > 6, which can be used as a benchmark for reionization models. Model-independent reionization constraints from the cosmic microwave background (CMB) optical depth and Ly α and Ly β forest dark pixel fraction produce $\dot{N}_\textrm {ion}$ evolution ($\mathrm{ d}\log _{10}\dot{\mathbf {N}}_{\bf ion}/\mathrm{ d}z|_{z=6\rightarrow 8} = -0.31\pm 0.35$ dex) consistent with the declining UV luminosity density of galaxies, assuming constant ionizing photon escape fraction and efficiency. Including measurements from Ly α damping of galaxies and quasars produces a more rapid decline: $\mathrm{ d}\log _{10}\dot{\mathbf {N}}_{\bf ion}/\mathrm{ d}z|_{z=6\rightarrow 8} =-0.44\pm 0.22$ dex, steeper than the declining galaxy luminosity density (if extrapolated beyond $M_\rm{\small UV}\gtrsim -13$), and constrains the mid-point of reionization to z = 6.93 ± 0.14.

The TopHat Cosmic Microwave Background Anisotropy Experiment

2005 ◽  
Vol 201 ◽  
pp. 65-70
Author(s):  
Robert F. Silverberg ◽  
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Background Radiation ◽  
High Sensitivity ◽  
Microwave Background ◽  
Long Duration ◽  
Cosmic Microwave Background Anisotropy ◽  
Microwave Background Radiation ◽  
The Universe ◽  
Large Scale Structure Formation

We have developed a balloon-borne experiment to measure the Cosmic Microwave Background Radiation anisotropy on angular scales from ˜50° down to ˜20′. The instrument observes at frequencies between 150 and 690 GHz and will be flown on an Antarctic circumpolar long duration flight. To greatly improve the experiment performance, the front-end of the experiment is mounted on the top of the balloon. With high sensitivity, broad sky coverage, and well-characterized systematic errors, the results of this experiment can be used to strongly constrain cosmological models and probe the early stages of large-scale structure formation in the Universe.

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.

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