scholarly journals 21-cm power spectrum and ionization bias as a probe of long-mode modulated non-Gaussian sky

2019 ◽  
Vol 488 (4) ◽  
pp. 5941-5951
Author(s):  
Shahram Khosravi ◽  
Amirabbas Ghazizadeh ◽  
Shant Baghram
Keyword(s):  
Power Spectrum ◽  
Background Radiation ◽  
Neutral Hydrogen ◽  
Hydrogen Distribution ◽  
Microwave Background ◽  
Power Asymmetry ◽  
Angular Power Spectrum ◽  
Long Wavelength ◽  
Microwave Background Radiation ◽  
Non Gaussian

ABSTRACT The observed hemispherical power asymmetry in cosmic microwave background radiation can be explained by long-wavelength mode (long-mode) modulation. In this paper, we study the possibility of detecting this effect in the angular power spectrum of the 21-cm brightness temperature. For this task, we study the effect of the neutral hydrogen distribution on the angular power spectrum. This is done by formulating the bias parameter of the ionized fraction to the underlying matter distribution. We also discuss the possibility that the long-mode modulation is accompanied by a primordial non-Gaussianity of local type. In this case, we obtain the angular power spectrum with two effects of primordial non-Gaussianity and long-mode modulation. Finally, we show that the primordial non-Gaussianity enhances the long-mode modulated power of the 21-cm signal via the non-Gaussian scale-dependent bias up to four orders of magnitude. Accordingly, observations of the 21-cm signal with upcoming surveys, such as the Square Kilometer Array (SKA), will probably be capable of detecting hemispherical power asymmetry in the context of long-mode modulation.

scholarly journals THE DEGENERACY PROBLEM IN LAMBDA-CDM COSMOLOGICAL MODELS

2011 ◽  
Vol 03 ◽  
pp. 246-253
Author(s):  
ARMANDO BERNUI
Keyword(s):  
Power Spectrum ◽  
Background Radiation ◽  
Cosmological Parameters ◽  
Power Spectra ◽  
Cosmological Models ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Statistical Property ◽  
Microwave Background Radiation ◽  
Degeneracy Problem

Recent measurements of the cosmic microwave background radiation (CMB) from the WMAP satellite led to formulate a successful concordance cosmological model, termed ΛCDM. This model satisfactorily explains the origin and structure of the CMB temperature fluctuations, from small to large angular scales, and moreover it accurately fits –with only six parameters– the CMB angular power spectrum. Despite of their triumphs in describing the observed WMAP data, we notice that some ΛCDM cosmological parameters can attain, due to their error bars, slightly different values and this degree of freedom could produce a significant impact in our understanding of the primordial universe. We are talking about the degeneracy problem, that is cosmological models with parameters that are a little bit different from those given by the ΛCDM model but fits equally well the angular power spectrum of the CMB data. Our interest here is to investigate the Gaussian statistical property, at large angular scales, in two sets of Monte Carlo CMB maps produced by seeding them with slightly different ΛCDM angular power spectra.

scholarly journals Scalar–Tensor–Vector Modified Gravity in Light of the Planck 2018 Data

Universe ◽  
2021 ◽  
Vol 7 (10) ◽  
pp. 358
Author(s):  
John W. Moffat ◽  
Viktor Toth
Keyword(s):  
Power Spectrum ◽  
Background Radiation ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Modified Theories Of Gravity ◽  
Microwave Background ◽  
Computational Tools ◽  
Angular Power Spectrum ◽  
Microwave Background Radiation ◽  
Theories Of Gravity ◽  
Theories Of Gravitation

The recent data release by the Planck satellite collaboration presents a renewed challenge for modified theories of gravitation. Such theories must be capable of reproducing the observed angular power spectrum of the cosmic microwave background radiation. For modified theories of gravity, an added challenge lies in the fact that standard computational tools do not readily accommodate the features of a theory with a variable gravitational coupling coefficient. An alternative is to use less accurate but more easily modifiable semianalytical approximations to reproduce at least the qualitative features of the angular power spectrum. We extend a calculation that was used previously to demonstrate compatibility between the Scalar–Tensor–Vector–Gravity (STVG) theory, also known by the acronym MOG, and data from the Wilkinson Microwave Anisotropy Probe (WMAP) to show the consistency between the theory and the newly released Planck 2018 data. We find that within the limits of this approximation, the theory accurately reproduces the features of the angular power spectrum.

scholarly journals Microwave Background Anisotropies in a Baryon-Dominated Universe

1988 ◽  
Vol 130 ◽  
pp. 513-513
Author(s):  
Yasushi Suto ◽  
Naoteru Gouda ◽  
Misao Sasaki
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Background Radiation ◽  
Cosmic Microwave Background Radiation ◽  
Microwave Background ◽  
Gauge Invariant ◽  
Invariant Method ◽  
Angular Scale ◽  
Microwave Background Radiation ◽  
Image Position

We have calculated the anisotropies of the cosmic microwave background radiation in a baryon-dominated model (BDM), using a gauge invariant method. The results on a 4.5′ angular scale are as follows (h = 0.5 and initially Zel'dovich power spectrum assumed):

scholarly journals Cosmic Strings and Their Induced Non-Gaussianities in the Cosmic Microwave Background

2010 ◽  
Vol 2010 ◽  
pp. 1-28 ◽  
Author(s):  
Christophe Ringeval
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Early Universe ◽  
Cosmic Strings ◽  
Point Function ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Gravitational Perturbations ◽  
The One ◽  
Non Gaussian

Motivated by the fact that cosmological perturbations of inflationary quantum origin were born Gaussian, the search for non-Gaussianities in the cosmic microwave background (CMB) anisotropies is considered as the privileged probe of nonlinear physics in the early universe. Cosmic strings are active sources of gravitational perturbations and incessantly produce non-Gaussian distortions in the CMB. Even if, on the currently observed angular scales, they can only contribute a small fraction of the CMB angular power spectrum, cosmic strings could actually be the main source of its non-Gaussianities. In this paper, after having reviewed the basic cosmological properties of a string network, we present the signatures Nambu-Goto cosmic strings would induce in various observables ranging from the one-point function of the temperature anisotropies to the bispectrum and trispectrum. It is shown that string imprints are significantly different than those expected from the primordial type of non-Gaussianity and could therefore be easily distinguished.

scholarly journals Long-wavelength measurements of the cosmic microwave background radiation spectrum

1987 ◽  
Vol 317 ◽  
pp. L45 ◽  
Author(s):  
George F. Smoot ◽  
Marc Bensadoun ◽  
Marco Bersanelli ◽  
Giovanni de Amici ◽  
Alan Kogut ◽  
...  
Keyword(s):  
Cosmic Microwave Background ◽  
Radiation Spectrum ◽  
Background Radiation ◽  
Cosmic Microwave Background Radiation ◽  
Microwave Background ◽  
Long Wavelength ◽  
Microwave Background Radiation

scholarly journals LARGE-ANGLE NON-GAUSSIANITY IN SIMULATED HIGH-RESOLUTION CMB MAPS

2011 ◽  
Vol 03 ◽  
pp. 286-293 ◽  
Author(s):  
ARMANDO BERNUI ◽  
MARCELO J. REBOUÇAS ◽  
ANTONIO F. F. TEIXEIRA
Keyword(s):  
Dimensionless Parameter ◽  
Angular Resolution ◽  
Background Radiation ◽  
Large Angle ◽  
High Angular Resolution ◽  
Microwave Background ◽  
Considerable Effort ◽  
Microwave Background Radiation ◽  
Non Gaussian ◽  
Temperature Maps

A detection or nondetection of primordial non-Gaussianity by using the cosmic microwave background radiation (CMB) offers a way of discriminating inflationary scenarios and testing alternative models of the early universe. This has motivated the considerable effort that has recently gone into the study of theoretical features of primordial non-Gaussianity and its detection in CMB data. Among such attempts to detect non-Gaussianity, there is a procedure that is based upon two indicators constructed from the skewness and kurtosis of large-angle patches of CMB maps, which have been proposed and used to study deviation from Gaussianity in the WMAP data (see Refs. 1 and 2). Simulated CMB maps equipped with realistic primordial non-Gaussianity are essential tools to test the viability of non-Gaussian indicators in practice, and also to understand the effect of systematics, foregrounds and other contaminants. In this work we extend and complement the results Refs. 1 and 2 by performing an analysis of non-Gaussianity of the high-angular resolution simulated CMB temperature maps endowed with non-Gaussianity of the local type, for which the level of non-Gaussianity is characterized by the dimensionless parameter [Formula: see text].

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