Volume 78, Number 1, April 2007
Article Number 19001
Number of page(s) 6
Section Geophysics, Astronomy and Astrophysics
Published online 19 March 2007
EPL, 78 (2007) 19001
DOI: 10.1209/0295-5075/78/19001

Deviation from Gaussianity in the cosmic microwave background temperature fluctuations

Armando Bernui1, Constantino Tsallis2 and Thyrso Villela1

1  Instituto Nacional de Pesquisas Espaciais, Divisão de Astrofísica - Av. dos Astronautas 1758, 12227-010 São José dos Campos, SP, Brazil
2  Centro Brasileiro de Pesquisas Físicas - Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ, Brazil

received 6 October 2006; accepted in final form 19 February 2007; published April 2007
published online 19 March 2007

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 $P^{{\rm CMB}}(\Delta T)$ of these data can be quite well fitted by the anomalous probability distribution emerging within nonextensive statistical mechanics, based on the entropy $S_q \equiv k \{ 1-\int \, \upd x \, [P(x)]^q \} /(q\!-\!1) $ ( $S_1 \!=\! - k \int \, \upd x \, P(x) \, {\rm ln}[P(x)] $). For the CMB frequencies analysed, $\nu =$ 40.7, 60.8, and 93.5 GHz, $P^{{\rm CMB}}(\Delta T)$ is well described by $P_{q}(\Delta T) \propto 1/[1+(q-1) B(\nu ) (\Delta T)^{2}]^{1/(q-1)}$, with $q=1.04 \pm 0.01$, 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, $P_{1}(\Delta T) \propto e^{-B(\nu )(\Delta T)^{2}}$ to fit the three-year data.

98.80.Es - Observational cosmology (including Hubble constant, distance scale, cosmological constant, early Universe, etc.).
98.70.Vc - Background radiations.
05.90.+m - Other topics in statistical physics, thermodynamics, and nonlinear dynamical systems.

© Europhysics Letters Association 2007