scholarly journals NON-GAUSSIANITY IN THE HILC FOREGROUND-REDUCED THREE-YEAR WMAP CMB MAP

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1411-1416 ◽  
Author(s):  
A. BERNUI ◽  
M. J. REBOUÇAS
Keyword(s):  
Early Universe ◽  
Large Angle ◽  
Single Frequency ◽  
Considerable Effort ◽  
Frequency Bands ◽  
Alternative Models ◽  
Wmap Data ◽  
Inflationary Models

The detection or non-detection of primordial non-Gaussianity in the CMB data is essential not only to test alternative models of the physics of the early universe but also to discriminate among classes of inflationary models. Given this far-reaching consequences of such a non-Gaussianity detection for our understanding of the physics of the early universe, it is important to employ alternative indicators in order to have further information about the Gaussianity features of CMB that may be helpful for identifying their origins. In this way, a considerable effort has recently gone into the design of non-Gaussianity indicators, and in their application in the search for deviation from Gaussianity in the CMB data. Recently we have proposed two new large-angle non-Gaussianity indicators which provide measures of the departure from Gaussianity on large angular scales. We have used these indicators to carry out analyses of Gaussianity of the single frequency bands and of the available foreground-reduced five-year maps with and without the KQ75 mask. Here we extend and complement these studies by performing a new analysis of deviation from Gaussianity of the three-year harmonic ILC (HILC) foreground-reduced full-sky and KQ75 masked maps obtained from WMAP data. We show that these full-sky foreground-reduced maps present a significant deviation from Gaussianity, which is brought down to a level of consistency with Gaussianity when the KQ75 mask is employed.

scholarly journals A STUDY OF GAUSSIANITY IN CMB BAND MAPS

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1405-1409 ◽  
Author(s):  
A. BERNUI ◽  
M. J. REBOUÇAS ◽  
A. F. F. TEIXEIRA
Keyword(s):  
Early Universe ◽  
Alternative Models ◽  
W Band ◽  
Alternative Scenarios ◽  
Inflationary Models ◽  
Rule Out

The detection of non-Gaussianity in the CMB data would rule out a number of inflationary models. A null detection of non-Gaussianity, instead, would exclude alternative models for the early universe. Thus, a detection or non-detection of primordial non-Gaussianity in the CMB data is crucial to discriminate among inflationary models, and to test alternative scenarios. However, there are various non-cosmological sources of non-Gaussianity. This makes important to employ different indicators in order to detect distinct forms of non-Gaussianity in CMB data. Recently, we proposed two new indicators to measure deviation from Gaussianity on large angular scales, and used them to study the Gaussianity of the raw band WMAP maps with and without the KQ75 mask. Here we extend this work by using these indicators to perform similar analyses of deviation from Gaussianity of the foreground-reduced Q, V, and W band maps. We show that there is a significant deviation from Gaussianity in the considered full-sky maps, which is reduced to a level consistent with Gaussianity when the KQ75 mask is employed.

scholarly journals Inflationary universe models and clustering of quasar red shifts

1986 ◽  
Vol 119 ◽  
pp. 509-510
Author(s):  
C. Sivaram
Keyword(s):  
Cosmological Model ◽  
Early Universe ◽  
Hubble Constant ◽  
Matter Density ◽  
Inflationary Universe ◽  
Expansion Phase ◽  
Exponential Expansion ◽  
The Universe ◽  
Inflationary Models ◽  
Universe Models

Recently it has been shown that many of the puzzling features of conventional cosmological models (such as the horizon and flatness problems) could be explained by invoking inflationary models of the early universe with an exponential expansion phase at very early epochs. These models have the added advantage that they are able to make a definite prediction about the present matter density in the universe, i.e. they require that the density be exactly equal to the closure density which in turn can be easily estimated from the Hubble constant now known to within a factor of two. Now if one goes back to an earlier idea that explored the possibility of unusual clustering of quasar redshifts around z = 2 or 3, we get an example of another cosmological model with a definite prediction for the present overall matter density. This is a modified version of the Eddington-Lemaitre type of model which naturally accommodates such features as a clustering of quasars at certain epochs. From these models one can get a prediction for the present matter density which would be an involved function of the Hubble constant and the redshifts at which such clustering occurs. It can be shown that if such clustering had occurred at any z, the present matter density predicted would be substantially smaller than the corresponding closure density. The conclusion is that any clustering of quasar redshifts is incompatiable with inflationary universe models, indirectly providing observational support for these new theories.

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.

Методика оценки возможности распределения (выделения) полос частот для одночастотных систем

2020 ◽  
Author(s):  
V.S. Yakimenko
Keyword(s):  
Radio Frequency ◽  
Frequency Spectrum ◽  
Frequency Band ◽  
Electromagnetic Compatibility ◽  
Single Frequency ◽  
Frequency Bands ◽  
Radio Frequency Spectrum

A technique of estimating the possibility of distribution (allocation) of frequency bands for single-frequency systems is proposed. The technique provides the valueof the radio-frequency spectrum unavailable for singlefrequency systems in the specified territorial area and frequency band according to the conditions of electromagnetic compatibility with existing radioelectronic equipment. A system of criteria for evaluating the possibility of allocating frequency bands for singlefrequency systems is proposed. Предложена методика оценки возможности распределения (выделения) полос частот для одночастотных телекоммуникационных систем. Методика предусматривает определение величины адиочастотного спектра (РЧС), недоступного для одночастотных систем в заданном территориальном районе и полосе частот по условиям электромагнитной совместимости (ЭМС) с существующими радиоэлектронными средствами (РЭС). При этом учитывается групповое помеховое воздействие радиоэлектронных средств одночастотных систем на существующие РЭС. Предложена система критериев оценки достаточности доступной части спектра для удовлетворения потребностей в этом ресурсе одночастотных систем.

scholarly journals Searching for non-Gaussianity in the Planck data

2014 ◽  
Vol 10 (S306) ◽  
pp. 147-149
Author(s):  
Marcelo J. Rebouças ◽  
Armando Bernui
Keyword(s):  
Cosmic Microwave Background ◽  
Early Universe ◽  
Large Angle ◽  
Statistical Procedure ◽  
Statistical Properties ◽  
Microwave Background ◽  
Planck Data ◽  
Angle Deviation

AbstractThe statistical properties of the temperature anisotropies and polarization of the of cosmic microwave background (CMB) radiation offer a powerful probe of the physics of the early universe. In recent works a statistical procedure based upon the calculation of the kurtosis and skewness of the data in patches of CMB sky-sphere has been proposed and used to investigate the large-angle deviation from Gaussianity in WMAP maps. Here we briefly address the question as to how this analysis of Gaussianity is modified if the foreground-cleaned Planck maps are considered. We show that although the foreground-cleaned Planck maps present significant deviation from Gaussianity of different degrees when a less severe mask is used, they become consistent with Gaussianity, as detected by our indicators, when masked with the union mask U73.

scholarly journals TESTING GAUSSIANITY IN THE WMAP DATA OF OT FOREGROUND REDUCED MAP

2009 ◽  
Vol 24 (08n09) ◽  
pp. 1664-1668 ◽  
Author(s):  
ARMANDO BERNUI ◽  
MARCELO J. REBOUÇAS
Keyword(s):  
Cosmic Microwave Background ◽  
Linear Combination ◽  
Microwave Background ◽  
Considerable Effort ◽  
Cleaning Procedure ◽  
Wmap Data

A considerable effort has recently gone into the study of Gaussianity of cosmic microwave background (CMB) data. Among such attempts, there is one with two non-Gaussianity indicators, proposed by the authors, and used in a search for significant deviation from Gaussianity in the WMAP internal linear combination (ILC) maps with the KQ75 mask. Here we extend and complement these results by performing a similar analysis for the de Oliveira-Costa and Tegmark (OT) WMAP three-year KQ75 masked map, in which the foreground is reduced through a different statistical cleaning procedure.

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].

scholarly journals Estimation and Analysis of BDS2 and BDS3 Differential Code Biases and Global Ionospheric Maps Using BDS Observations

2021 ◽  
Vol 13 (3) ◽  
pp. 370
Author(s):  
Min Li ◽  
Yunbin Yuan
Keyword(s):  
Assessment System ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
International Gnss Service ◽  
Efficient Manner ◽  
Frequency Bands ◽  
Measurement Science ◽  
Receiver Dcb ◽  
Global Ionospheric Maps ◽  
German Aerospace

Following the continuous and stable regional service of BDS2, the BDS3 officially announced its global service in July 2020. To fully take advantage of the new multi-frequency BDS3 signals in ionosphere sensing and positioning, it is essential to understand the characteristics of the differential code bias (DCB) of new BDS3 signals and BDS performance in global ionospheric maps (GIMs) estimation. This article presents an evaluation of the characteristics of 13 types of BDS DCBs and the accuracy of BDS-based GIM based on the data provided by the International GNSS Service (IGS) and International GNSS Monitoring and Assessment System (iGMAS) for the first time. The GIMs and DCBs are estimated by the APM (Innovation Academy for Precision Measurement Science and Technology) method in a time efficient manner, which can be divided into two main steps. The first step is to produce GIMs based on BDS observations at the B1I, B2I and B3I signals, and the second step is to estimate DCBs among the other frequency bands by removing the ionospheric delay using the precomputed GIMs. Good agreement is found between the APM-based satellite DCB estimates and those from the Chinese Academy of Sciences (CAS) and the German Aerospace Center (DLR) at levels of 0.26 ns and 0.18 ns, respectively. The results, spanning one month, show that the stability of BDS DCB estimates among different frequency bands are related to the contributed observations, and the receiver DCB estimates represent larger STD values than the satellite DCB estimates. The differences in receiver DCB estimates between BDS2 and BDS3 are found to be related to the types of receivers and antennas and firmware version, and the bias of the JAVAD receivers reaches 1.03 ns. The results also indicate that the difference in the single-frequency standpoint positioning (SPP) accuracy using GPS-based and BDS-based GIMs for ionospheric delay corrections is less than 0.03 m in both the horizontal and vertical directions.

scholarly journals Evidence of a truncated spectrum in the angular correlation function of the cosmic microwave background

2018 ◽  
Vol 610 ◽  
pp. A87 ◽  
Author(s):  
F. Melia ◽  
M. López-Corredoira
Keyword(s):  
Correlation Function ◽  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Angular Correlation ◽  
Early Universe ◽  
Large Angle ◽  
Microwave Background ◽  
Slow Roll ◽  
Angular Correlation Function ◽  
Slow Roll Inflation

Aim. The lack of large-angle correlations in the fluctuations of the cosmic microwave background (CMB) conflicts with predictions of slow-roll inflation. But while probabilities (≲0.24%) for the missing correlations disfavour the conventional picture at ≳3σ, factors not associated with the model itself may be contributing to the tension. Here we aim to show that the absence of large-angle correlations is best explained with the introduction of a non-zero minimum wave number kmin for the fluctuation power spectrum P(k). Methods. We assumed that quantum fluctuations were generated in the early Universe with a well-defined power spectrum P(k), although with a cut-off kmin ≠ 0. We then re-calculated the angular correlation function of the CMB and compared it with Planck observations. Results. The Planck 2013 data rule out a zero kmin at a confidence level exceeding 8σ. Whereas purely slow-roll inflation would have stretched all fluctuations beyond the horizon, producing a P(k) with kmin = 0 – and therefore strong correlations at all angles – a kmin ≠ 0 would signal the presence of a maximum wavelength at the time (tdec) of decoupling. This argues against the basic inflationary paradigm, and perhaps even suggests non-inflationary alternatives, for the origin and growth of perturbations in the early Universe. In at least one competing cosmology, the Rh = ct universe, the inferred kmin corresponds to the gravitational radius at tdec.

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