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9 papers · 1 filter
Limits on Isocurvature Perturbations from Non-Gaussianity in WMAP Temperature Anisotropies
Chiaki Hikage, Kazuya Koyama, Takahiko Matsubara +2
We study the effect of primordial isocurvature perturbations on non-Gaussian properties of CMB temperature anisotropies. We consider generic forms of the non-linearity of isocurvat…
Adiabatic fluctuations from cosmic strings in a contracting universe
Robert H. Brandenberger, Tomo Takahashi, Masahide Yamaguchi
We show that adiabatic, super-Hubble, and almost scale invariant density fluctuations are produced by cosmic strings in a contracting universe. An essential point is that isocurvat…
Primordial Curvature Fluctuation and Its Non-Gaussianity in Models with Modulated Reheating
Kazuhide Ichikawa, Teruaki Suyama, Tomo Takahashi +1
We investigate non-Gaussianity in the modulated reheating scenario where fluctuations of the decay rate of the inflaton generate adiabatic perturbations, paying particular attentio…
Probing the Effective Number of Neutrino Species with Cosmic Microwave Background
Kazuhide Ichikawa, Toyokazu Sekiguchi, Tomo Takahashi
We discuss how much we can probe the effective number of neutrino species N_nu with cosmic microwave background alone. Using the data of WMAP, ACBAR, CBI and BOOMERANG experiments,…
Non-Gaussianity, Spectral Index and Tensor Modes in Mixed Inflaton and Curvaton Models
Kazuhide Ichikawa, Teruaki Suyama, Tomo Takahashi +1
We study non-Gaussianity, the spectral index of primordial scalar fluctuations and tensor modes in models where fluctuations from the inflaton and the curvaton can both contribute…
Primordial Helium Abundance from CMB: a constraint from recent observations and a forecast
Kazuhide Ichikawa, Toyokazu Sekiguchi, Tomo Takahashi
We studied a constraint on the primordial helium abundance Y_p from current and future observations of CMB. Using the currently available data from WMAP, ACBAR, CBI and BOOMERANG,…