The influence of super-horizon scales on cosmological observables generated during inflation

Abstract

Using the techniques of out-of-equilibrium field theory, we study the\ninfluence on the properties of cosmological perturbations generated during\ninflation on observable scales coming from fluctuations corresponding today to\nscales much bigger than the present Hubble radius. We write the effective\naction for the coarse-grained inflaton perturbations integrating out the\nsub-horizon modes, which manifest themselves as a colored noise and lead to\nmemory effects. Using the simple model of a scalar field with cubic\nself-interactions evolving in a fixed de Sitter background, we evaluate the\ntwo- and three-point correlation function on observable scales. Our basic\nprocedure shows that perturbations do preserve some memory of the\nsuper-horizon-scale dynamics, in the form of scale-dependent imprints in the\nstatistical moments. In particular, we find a blue tilt of the power-spectrum\non large scales, in agreement with the recent results of the WMAP collaboration\nwhich show a suppression of the lower multipoles in the Cosmic Microwave\nBackground anisotropies, and a substantial enhancement of the intrinsic\nnon-Gaussianity on large scales\n