scholarly journals Searching for non-Gaussianity in the Planck data

2014 ◽  
Vol 10 (S306) ◽  
pp. 147-149
Author(s):  
Marcelo J. Rebouças ◽  
Armando Bernui

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.

2018 ◽  
Vol 610 ◽  
pp. A87 ◽  
Author(s):  
F. Melia ◽  
M. López-Corredoira

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.


1990 ◽  
Vol 139 ◽  
pp. 398-399
Author(s):  
R. D. Davies ◽  
R. A. Watson ◽  
R. Rebolo ◽  
J. Beckman ◽  
A. N. Lasenby

Deep observations of the cosmic microwave background (CMB) have been made at 10 GHz with beamwidths of 5° and 8° using a triple-beam technique, which greatly reduces atmospheric effects. Significant signals are detected with an rms of ΔT/T ~ 4×10−5. These signals could be intrinsic to the CMB and are providing fundamental information about galaxy formation in the early universe. A component of this 10 GHz emission may be coming from galactic synchrotron features. This galactic contribution will be elucidated in forthcoming 15 and 30 GHz observations.


2014 ◽  
Vol 13 (4) ◽  
pp. 337-339 ◽  
Author(s):  
Abraham Loeb

AbstractIn the redshift range 100≲(1+z)≲137, the cosmic microwave background (CMB) had a temperature of 273–373 K (0–100°C), allowing early rocky planets (if any existed) to have liquid water chemistry on their surface and be habitable, irrespective of their distance from a star. In the standard ΛCDM cosmology, the first star-forming halos within our Hubble volume started collapsing at these redshifts, allowing the chemistry of life to possibly begin when the Universe was merely 10–17 million years old. The possibility of life starting when the average matter density was a million times bigger than it is today is not in agreement with the anthropic explanation for the low value of the cosmological constant.


2016 ◽  
Vol 93 (12) ◽  
Author(s):  
Christian T. Byrnes ◽  
Donough Regan ◽  
David Seery ◽  
Ewan R. M. Tarrant

2009 ◽  
Vol 18 (14) ◽  
pp. 2329-2335 ◽  
Author(s):  
IVÁN AGULLÓ ◽  
JOSÉ NAVARRO-SALAS ◽  
GONZALO J. OLMO ◽  
LEONARD PARKER

Inflationary cosmology has proven to be the most successful at predicting the properties of the anisotropies observed in the cosmic microwave background (CMB). In this essay we show that quantum field renormalization significantly influences the generation of primordial perturbations and hence the expected measurable imprint of cosmological inflation on the CMB. However, the new predictions remain in agreement with observation, and in fact favor the simplest forms of inflation. In the near future, observations of the influence of gravitational waves from the early universe on the CMB will test our new predictions.


2002 ◽  
Vol 17 (29) ◽  
pp. 4273-4280
Author(s):  
ALEJANDRO GANGUI

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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