Non-Gaussianity Analysis on WMAP Data

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In summary, The authors of the paper "Non-Gaussianity analysis on local morphological measures of WMAP data" suggest that the observed non-Gaussianity in the CMB temperature field is likely caused by the field itself, bringing into question the inflationary scenario in the concordance cosmological model. However, a more recent paper by McEwen et al has detected a high-significance non-Gaussian signal in the WMAP 5-year data using directional spherical wavelets. This signal is found to be localized in certain regions, and when these regions are excluded, the non-Gaussianity disappears. This raises the question of whether these regions are caused by actual microwave sources or other factors. Additionally, it has been discovered that the
  • #1
jal
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Found the following. I leave the comment to the experts.

http://infoscience.epfl.ch/record/108833/files/
Y. Wiaux, P. Vielva, R.B. Barreiro, E. MartÃnez-González and P. Vandergheynst, Non-Gaussianity analysis on local morphological measures of WMAP data, Mon. Not. R. Astron. Soc., Vol. 385, pp. 939, 2008.

“The observed non-Gaussianity is therefore probably to be imputed to the CMB temperature field itself, thereby questioning the basic inflationary scenario upon which the concordance cosmological model relies”
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Probing dark energy with steerable wavelets through correlation of WMAP and NVSS local morphological measures
Mcewenetal-MNRAS384-1289-2008
 
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  • #2
If anyone is interested in this rather specialized topic (WMAP observation of CMB non-Gaussianity) I would suggest they check out this more recent paper, which contains a REVIEW along with an interesting result.

http://arxiv.org/abs/0803.2157
A high-significance detection of non-Gaussianity in the WMAP 5-year data using directional spherical wavelets
Authors: J. D. McEwen, M. P. Hobson, A. N. Lasenby, D. J. Mortlock
(Submitted on 14 Mar 2008 (v1), last revised 29 Apr 2008 (this version, v2))

Abstract: We repeat the directional spherical real Morlet wavelet analysis, used to detect non-Gaussianity in the Wilkinson Microwave Anisotropy Probe (WMAP) 1-year and 3-year data (McEwen et al. 2005, 2006a), on the WMAP 5-year data. The non-Gaussian signal detected previously is present in the 5-year data at a slightly increased statistical significance of approximately 99%. Localised regions that contribute most strongly to the non-Gaussian signal are found to be very similar to those detected in the previous releases of the WMAP data. When the localised regions detected in the 5-year data are excluded from the analysis the non-Gaussian signal is eliminated.
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It seems that dozens of research groups have found non-Gaussian signal in the WMAP data and scores of papers have been published about it.

McEwen et al are at Cambridge and at Blackett Lab---they seem very much on top of this subject and they provide a map (Figure 4) with a few isolated dots on it where the non-Gaussianity is localized.
If one assumes that these few dots are unexplained sources of the non-Gaussian component and eliminates them, then the non-Gaussianity goes away. According to them.

As I am not an expert in this, I'd toss this out as a question in case anyone is interested. It's not of earthquake importance :smile: but could it be that the overall random mottling of the CMB temperature map is essentially perfect but has a few little blemishes caused by actual microwave sources----or otherwise explainable?
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BTW it now seems that the big "Void" people were talking about some 6 months ago is possibly merely an artifact of the data analysis and not really there.
The report came out recently. Don't know if anyone has posted on it yet.
 
  • #3
A question: If unknown contamination effects are present in the WMAP data, what is the probability they would result in non-gaussian artifacts?
 

What is Non-Gaussianity Analysis on WMAP Data?

Non-Gaussianity Analysis on WMAP Data is a statistical analysis technique used by scientists to study the non-Gaussian properties of the cosmic microwave background (CMB) radiation data collected by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite. This analysis helps to understand the early universe and the processes that shaped it.

Why is Non-Gaussianity Analysis on WMAP Data important?

Non-Gaussianity Analysis on WMAP Data is important because it provides valuable insights into the early universe and helps to test and refine theories of cosmology. It can also reveal any anomalies or deviations from the expected Gaussian distribution of the CMB, which can provide clues to the physics of the universe.

What are the main methods used in Non-Gaussianity Analysis on WMAP Data?

The main methods used in Non-Gaussianity Analysis on WMAP Data include the use of statistical tools such as the bispectrum and non-Gaussianity parameters, as well as the analysis of higher-order correlations in the CMB data. These methods help to detect any non-Gaussian features in the data and quantify their significance.

What have been some of the key findings from Non-Gaussianity Analysis on WMAP Data?

Non-Gaussianity Analysis on WMAP Data has revealed several important findings, including evidence for non-Gaussian features in the CMB temperature fluctuations, as well as deviations from the expected Gaussian distribution in the polarization data. These findings have helped to refine cosmological models and provide new insights into the physics of the early universe.

What are some potential applications of Non-Gaussianity Analysis on WMAP Data?

Non-Gaussianity Analysis on WMAP Data has potential applications in various fields such as cosmology, astrophysics, and particle physics. It can help to test and validate theories of the early universe, constrain the properties of dark matter and dark energy, and provide new insights into the origin and evolution of the universe.

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