Quantum noises and the large scale structure

Abstract

We propose that cosmological density perturbation may originate from passive fluctuations of the inflaton, which are induced by colored quantum noise due to the coupling of the inflaton to the quantum environment. At small scales, the fluctuations grow with time to become nearly scale-invariant. However, the larger-scale modes cross out the horizon earlier and do not have enough time to grow, thus resulting in a suppression of the density perturbation. This may explain the observed low quadrupole in the CMB anisotropy data and and potentially unveil the initial time of inflation. We also discuss the implications to the running spectral index and the non-Gaussianity of the primordial density perturbation.