Non-Gaussianity Analysis on WMAP Data

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Recent analyses of WMAP data indicate significant non-Gaussianity in the cosmic microwave background (CMB) temperature field, raising questions about the inflationary model of cosmology. Studies, including one by McEwen et al., have confirmed the presence of non-Gaussian signals in the WMAP 5-year data, with high statistical significance. These signals appear localized to specific regions, suggesting that excluding these areas can eliminate the non-Gaussianity. The discussion also highlights concerns about potential contamination in the data that could create misleading artifacts. Overall, the findings challenge existing cosmological theories and underscore the complexity of interpreting CMB data.
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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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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.
 
A question: If unknown contamination effects are present in the WMAP data, what is the probability they would result in non-gaussian artifacts?
 

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