Quantifying nonlinear contributions to the CMB bispectrum in Synchronous gauge
Pettinari, Guido Walter (Institute of Cosmology and Gravitation)

The upcoming PLANCK experiment will allow us to test models of inflation with unprecedented accuracy. In particular, the measurement of the CMB bispectrum will provide a stringent constraint on the amount of non-Gaussianity in the initial conditions of our Universe. The detection of primordial non-Gaussianity would be a direct probe of the early Universe physics, and would provide information on the particle fields present at the time. However, a recent paper by Pitrou, Bernardeau, Uzan (2010) points out that the non-linear evolution coming from Einstein equations significantly contributes to the observed non-Gaussianity, even for completely Gaussian initial conditions. We aim to quantify this "noise" over the primordial signal by means of a full integration of the Boltzmann-Einstein system of equations at second-perturbative order. During the talk, I shall highlight the differences with the first-order approach, discuss gauge issues, show the relevant equations, and present some preliminary results.