Séminaire / Seminar GReCO |
| « Stochastic inflation with colored noise: low CMB multipoles suppression and non-Gaussianity » |
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Marcello Musso |
| In the stochastic formulation of inflation, the quantum fluctuations arising on small scales are collected in a classical noise term that perturbs the long-wavelength dynamics. We describe the derivation of the Langevin equation for the perturbations, and we analyze the statistical properties of its solution in dependence on the characteristics of the noise (white vs colored). We provide a calculation of the power-spectrum of the fluctuations in the case of a colored noise, and we show that a blue tilt on the largest observable scales is found when one properly accounts for the homogeneity of our local patch of the Universe just before it crosses the Hubble radius. This is in agreement with the WMAP data showing an unexpected suppression of the low multipoles of the CMB anisotropy. Using the simplified model of a test scalar field with cubic self-interaction, we show how the probability distribution of the fluctuations on observable scales do preserve some memory of the higly non-Gaussian ultra-large-scale dynamics. As a consequence of this cross-talk the intrinsic non-Gaussianity is substantially enhanced also on observable scales. |
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jeudi 28 octobre 2004 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |