Deviation from Gaussianity in the cosmic microwave background temperature fluctuations

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Abstract
Recent measurements of the temperature fluctuations of the cosmic microwave background (CMB) radiation from the WMAP satellite provide indication of a non-Gaussian behavior. Although the observed feature is small, it is detectable and analyzable. Indeed, the temperature distribution PCMB(ΔT) of these data can be quite well fitted by the anomalous probability distribution emerging within nonextensive statistical mechanics, based on the entropy Sq ≡ k{1− ∫ dx[P(x)]q}/(q−1) (S1 ≡ −k ∫ dxP(x)ln[P(x)]). For the CMB frequencies analysed, ν = 40.7, 60.8, and 93.5 GHz, PCMB(ΔT) is well described by Pq(ΔT) ∝ 1/[1+(q−1) B(ν) (ΔT)2]1/(q−1), with q = 1.04 ± 0.01, the strongest non-Gaussian contribution coming from the South-East sector of the celestial sphere. Moreover, Monte Carlo simulations exclude, at the 99% confidence level, P1(ΔT) ∝ e−B(ν)(ΔT)2 to fit the three-year data.
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