Non-Gaussianity from inflation: theory and observations

126

121

We study the curvaton scenario using gauge-invariant second order perturbation theory and solving the governing equations numerically. Focusing on large scales we calculate the non-linearity parameter fNL in the two-fluid curvaton model and compare our results with previous analytical studies employing the sudden decay approximation. We find good agreement of the two approaches for large curvaton energy densities at curvaton decay, Ω σdec , but significant differences of up to 10% for small Ω σdec .

Section: The Non-linearity Parameter Fnl: Results and Discussionmentioning

confidence: 89%

A numerical study of non-Gaussianity in the curvaton scenario

Malik¹,

Lyth²

2006

126

121

“…(37) and (38) up to the second order, we can explicitly express ζ r and ζ CDM in terms of ζ φ and ζ σ as…”

Section: Cdm From the Inflaton And Direct Decay Of The Curvatonmentioning

confidence: 99%

“…In this section we investigate the effects of the non-linear isocurvature perturbation on the CMB anisotropy, following the notations used in [38,39]. Since the adiabatic and isocurvature perturbations have quite different properties regarding their imprints on the CMB anisotropy, we need to correctly evaluate the bispectrum of the temperature anisotropy in the presence of both adiabatic and isocurvature non-Gaussianity.…”

Section: Cmb Temperature Anisotropymentioning

confidence: 99%

A general analysis of non-gaussianity from isocurvature perturbations

Kawasaki

Nakayama

Sekiguchi

et al. 2009

Light scalars may be ubiquitous in nature, and their quantum fluctuations can produce large non-Gaussianity in the cosmic microwave background temperature anisotropy. The non-Gaussianity may be accompanied with a small admixture of isocurvature perturbations, which often have correlations with the curvature perturbations. We present a general method to calculate the non-Gaussianity in the adiabatic and isocurvature perturbations with and without correlations, and see how it works in several explicit examples. We also show that they leave distinct signatures on the bispectrum of the cosmic microwave background temperature fluctuations.

“…They are found to have a nearly flat power spectrum, and to be close to Gaussian. Non-Gaussian effects (see [1] for a review) might be detected in the future and can provide a powerful tool to discriminate between different inflation models. There is therefore a large interest in calculating the statistical properties of the primordial cosmological perturbations for different inflation models.…”

Section: Introductionmentioning

confidence: 99%

Classical approximation to quantum cosmological correlations

Meulen¹,

Smit²

2007

Abstract:We investigate up to which order quantum effects can be neglected in calculating cosmological correlation functions after horizon exit. As a toy model, we study φ 3 theory on a de Sitter background for a massless minimally coupled scalar field φ. We find that for tree level and one loop contributions in the quantum theory, a good classical approximation can be constructed, but for higher loop corrections this is in general not expected to be possible. The reason is that loop corrections get non-negligible contributions from loop momenta with magnitude up to the Hubble scale H, at which scale classical physics is not expected to be a good approximation to the quantum theory. An explicit calculation of the one loop correction to the two point function, supports the argument that contributions from loop momenta of scale H are not negligible. Generalization of the arguments for the toy model to derivative interactions and the curvature perturbation leads to the conclusion that the leading orders of non-Gaussian effects generated after horizon exit, can be approximated quite well by classical methods. Furthermore we compare with a theorem by Weinberg. We find that growing loop corrections after horizon exit are not excluded, even in single field inflation.