1202.4890 (Etsuko Kawakami et al.)

Non-Gaussian isocurvature perturbations in dark radiation    [PDF]

Etsuko Kawakami, Masahiro Kawasaki, Koichi Miyamoto, Kazunori Nakayama, Toyokazu Sekiguchi

We study non-Gaussian properties of the isocurvature perturbations in the
dark radiation, which consists of the active neutrinos and extra light species,
if exist. We first derive expressions for the bispectra of primordial
perturbations which are mixtures of curvature and dark radiation isocurvature
perturbations. We also discuss CMB bispectra produced in our model and forecast
CMB constraints on the nonlinearity parameters based on the Fisher matrix
analysis. Some concrete particle physics motivated models are presented in
which large isocurvature perturbations in extra light species and/or the
neutrino density isocurvature perturbations as well as their non-Gaussianities
may be generated. Thus detections of non-Gaussianity in the dark radiation
isocurvature perturbation will give us an opportunity to identify the origin of
extra light species and lepton asymmetry.

View original: http://arxiv.org/abs/1202.4890