Non-Gaussian temperature fluctuations in the cosmic microwave background sky from a random Gaussian density field

1991 ◽  
Vol 375 ◽  
pp. 439 ◽  
Author(s):  
Roberto Scaramella ◽  
Nicola Vittorio
Keyword(s):  
Cosmic Microwave Background ◽  
Temperature Fluctuations ◽  
Density Field ◽  
Microwave Background ◽  
Gaussian Density ◽  
Non Gaussian

scholarly journals Primordial Non-Gaussianity and Bispectrum Measurements in the Cosmic Microwave Background and Large-Scale Structure

2010 ◽  
Vol 2010 ◽  
pp. 1-64 ◽  
Author(s):  
Michele Liguori ◽  
Emiliano Sefusatti ◽  
James R. Fergusson ◽  
E. P. S. Shellard
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Initial Conditions ◽  
Temperature Fluctuations ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Future Prospects ◽  
Microwave Background ◽  
Galaxy Distribution ◽  
Non Gaussian

The most direct probe of non-Gaussian initial conditions has come from bispectrum measurements of temperature fluctuations in the Cosmic Microwave Background and of the matter and galaxy distribution at large scales. Such bispectrum estimators are expected to continue to provide the best constraints on the non-Gaussian parameters in future observations. We review and compare the theoretical and observational problems, current results, and future prospects for the detection of a nonvanishing primordial component in the bispectrum of the Cosmic Microwave Background and large-scale structure, and the relation to specific predictions from different inflationary models.

scholarly journals THE TOPOLOGY OF THE COSMIC MICROWAVE BACKGROUND ANISOTROPY ON THE SCALE ~1°

1996 ◽  
Vol 05 (04) ◽  
pp. 319-362 ◽  
Author(s):  
D.I. NOVIKOV ◽  
H.E. JØRGENSEN
Keyword(s):  
Cosmic Microwave Background ◽  
Random Field ◽  
Gaussian Noise ◽  
Gaussian Random Field ◽  
Cosmological Models ◽  
Topological Method ◽  
Microwave Background ◽  
Cosmic Microwave Background Anisotropy ◽  
Non Gaussian

In this paper we develop the theory of clusterization of peaks in a Gaussian random field. We have obtained new mathematical results from this theory and the theory of percolation and have proposed a topological method of analysis of sky maps based on these results. We have simulated 10°×10° sky maps of the cosmic microwave background anisotropy expected from different cosmological models with 0.5°–1° resolution in order to demonstrate how this method can be used for detection of non-Gaussian noise in the maps and detection of the Doppler-peak in the spectrum of perturbation of ΔT/T.

scholarly journals Isotropic non-Gaussian gNL-like toy models that reproduce cosmic microwave background anomalies

2019 ◽  
Vol 626 ◽  
pp. A13 ◽  
Author(s):  
F. K. Hansen ◽  
T. Trombetti ◽  
N. Bartolo ◽  
U. Natale ◽  
M. Liguori ◽  
...  
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Statistical Significance ◽  
Common Mechanism ◽  
Small Scale ◽  
Cold Spot ◽  
Microwave Background ◽  
Significance Level ◽  
Non Gaussian ◽  
Cmb Fluctuations

Context. Based on recent observations of the cosmic microwave background (CMB), claims of statistical anomalies in the properties of the CMB fluctuations have been made. Although the statistical significance of the anomalies remains only at the ∼2−3σ significance level, the fact that there are many different anomalies, several of which support a possible deviation from statistical isotropy, has motivated a search for models that provide a common mechanism to generate them. Aims. The goal of this paper is to investigate whether these anomalies could originate from non-Gaussian cosmological models, and to determine what properties these models should have. Methods. We present a simple isotropic, non-Gaussian class of toy models that can reproduce six of the most extensively studied anomalies. We compare the presence of anomalies found in simulated maps generated from the toy models and from a standard model with Gaussian fluctuations. Results. We show that the following anomalies, as found in the Planck data, commonly occur in the toy model maps: (1) large-scale hemispherical asymmetry (large-scale dipolar modulation), (2) small-scale hemispherical asymmetry (alignment of the spatial distribution of CMB power over all scales ℓ = [2, 1500]), (3) a strongly non-Gaussian hot or cold spot, (4) a low power spectrum amplitude for ℓ <  30, including specifically (5) a low quadrupole and an unusual alignment between the quadrupole and the octopole, and (6) parity asymmetry of the lowest multipoles. We note that this class of toy model resembles models of primordial non-Gaussianity characterised by strongly scale-dependent gNL-like trispectra.

scholarly journals EARLY UNIVERSE SOURCES FOR CMB NON-GAUSSIANITY

2002 ◽  
Vol 17 (29) ◽  
pp. 4273-4280
Author(s):  
ALEJANDRO GANGUI
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Early Universe ◽  
Microwave Background ◽  
Scale Invariant ◽  
Invariant Model ◽  
Primordial Power Spectrum ◽  
Initial States ◽  
Non Gaussian ◽  
Inflationary Models

In the framework of inflationary models with non-vacuum initial states for cosmological perturbations, we study non-Gaussian signatures on the cosmic microwave background (CMB) radiation produced by a broken-scale-invariant model which incorporates a feature at a privileged scale in the primordial power spectrum.

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