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.

scholarly journals Multiverse effects on the CMB angular correlation function in the framework of NCG

2017 ◽  
Vol 14 (04) ◽  
pp. 1750054
Author(s):  
Sahar Arabzadeh ◽  
Kamran Kaviani
Keyword(s):  
Correlation Function ◽  
Cosmic Microwave Background ◽  
Angular Correlation ◽  
Geometrical Structure ◽  
Space Time ◽  
X Rays ◽  
Photon Propagator ◽  
Microwave Background ◽  
Fundamental Level ◽  
Angular Correlation Function

Following many theories that predict the existence of the multiverse and by conjecture that our space-time may have a generalized geometrical structure at the fundamental level, we are interested in using a non-commutative geometry (NCG) formalism to study a suggested two-layer space that contains our 4-dimensional (4D) universe and a re-derived photon propagator. It can be shown that the photon propagator and a cosmic microwave background (CMB) angular correlation function are comparable, and if there exists such a multiverse system, the distance between the two layers can be estimated to be within the observable universe’s radius. Furthermore, this study revealed that our results are not limited to CMB but can be applied to many other types of radiation, such as X-rays.

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.

scholarly journals Probing Density Fluctuations in the Universe with the FIRST Radio Survey

1999 ◽  
Vol 183 ◽  
pp. 244-244
Author(s):  
C.M. Cress
Keyword(s):  
Correlation Function ◽  
Power Spectrum ◽  
Angular Correlation ◽  
Density Fluctuations ◽  
Linear Evolution ◽  
Angle Measurements ◽  
Model Predictions ◽  
Non Linear ◽  
Angular Correlation Function ◽  
The Universe

We compare the angular correlation function measured for FIRST sources (Becker et al., Cress et al.) with COBE-normalized CDM-model predictions (Cress & Kamionkowski). We note that uncertainties in the z-distribution do not affect the predictions dramatically and that the effects of non-linear evolution of the power spectrum are significant for θ<∼20′. We find the CF at larger angles to be sensitive to clustering of nearby sources. The smaller angle measurements, when combined with results from other surveys (Loan et al., Rengelink et al.) indicate that the bias required for the data to fit CDM models increases as the surveys probe deeper. We also point the reader to Refregier et al. for information on the use of weak lensing of FIRST sources in probing foreground mass.

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.

Slow-Roll Inflation and Cosmic Microwave Background Anisotropy Data

2000 ◽  
Vol 543 (2) ◽  
pp. L99-L102 ◽  
Author(s):  
Jérôme Martin ◽  
Alain Riazuelo ◽  
Dominik J. Schwarz
Keyword(s):  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Slow Roll ◽  
Cosmic Microwave Background Anisotropy ◽  
Slow Roll Inflation

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.

EFFECTS OF PRIMORDIAL MAGNETIC FIELD ON EARLY UNIVERSE

2008 ◽  
Vol 23 (17n20) ◽  
pp. 1695-1706 ◽  
Author(s):  
DAI G. YAMAZAKI ◽  
KIYOTOMO ICHIKI ◽  
KAJINO TOSHITAKA ◽  
GRANT J. MATHEWS
Keyword(s):  
Magnetic Field ◽  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Early Universe ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background ◽  
Primordial Magnetic Field

The existence of a primordial magnetic field (PMF) would affect both the temperature and polarization anisotropies of the cosmic microwave background (CMB) and the formation of the large scale structure(LSS). It also provides a plausible explanation for the disparity between observations and theoretical fits to the CMB power spectrum and the LSS. Here we report on calculations of not only the numerical power spectrum of the PMF, but also the correlations between the PMF power spectrum and the primary curvature perturbations.

SAMPLE VARIANCE IN LARGE-SCALE COSMIC MICROWAVE BACKGROUND ANISOTROPY MEASUREMENTS

1998 ◽  
Vol 07 (01) ◽  
pp. 89-96 ◽  
Author(s):  
KIN-WANG NG
Keyword(s):  
Correlation Function ◽  
Cosmic Microwave Background ◽  
Large Scale ◽  
Large Angle ◽  
Density Fluctuations ◽  
Sample Variance ◽  
Small Scale ◽  
Microwave Background ◽  
Cosmic Microwave Background Anisotropy ◽  
Computationally Intensive

The effects of limited sky coverage in large-angle cosmic microwave background anisotropy experiments are investigated by computing the variance of the angular two-point correlation function with an incomplete sphere. We find that, assuming a power spectrum of density fluctuations with spectral index n = 1, the Galactic cut of half-width 20° (40°) about the Equator made by the COBE DMR experiment would induce a sample variance on the rms temperature fluctuation [(ΔT/T) rms ]2 (or equivalently, the correlation function at zero lag), which is 12% (38%) greater than the cosmic variance with a whole sky coverage. This result is about two times smaller than the naive expectation that the cosmic variance is enhanced by a factor of [Formula: see text], where A is the solid angle sampled by the experiment. We also find that the sample variance of the correlation function at nonzero lag can approach the cosmic variance limit. Our approach provides an analytic way of finding a theoretical error to the theoretical prediction for a particular experiment (either large- or small-scale), without having recourse to computationally intensive Monte Carlo or maximum likelihood methods.

scholarly journals Exploring suppressed long-distance correlations as the cause of suppressed large-angle correlations

2019 ◽  
Vol 490 (4) ◽  
pp. 5174-5181
Author(s):  
Craig J Copi ◽  
James Gurian ◽  
Arthur Kosowsky ◽  
Glenn D Starkman ◽  
Hezi Zhang
Keyword(s):  
Correlation Function ◽  
Large Angle ◽  
Real Space ◽  
Harmonic Space ◽  
Microwave Background ◽  
Long Distance ◽  
Cosmic Microwave Background Temperature ◽  
Angular Correlation Function ◽  
Density Perturbations ◽  
Background Temperature

ABSTRACT The absence of large-angle correlations in the map of cosmic microwave background temperature fluctuations is among the well-established anomalies identified in full-sky and cut-sky maps over the past three decades. Suppressed large-angle correlations are rare statistical flukes in standard inflationary cosmological models. One natural explanation could be that the underlying primordial density perturbations lack correlations on large distance scales. To test this idea, we replace Fourier modes by a wavelet basis with compact spatial support. While the angular correlation function of perturbations can readily be suppressed, the observed monopole- and dipole-subtracted correlation function is not generally suppressed. This suggests that suppression of large-angle temperature correlations requires a mechanism that has both real-space and harmonic-space effects.

Sign in / Sign up

Export Citation Format

Share Document