Speaker: Toyokazu Sekiguchi (Nagoya)
Isocurvature perturbations are unique probes of physics in the very early Universe. If they are detected, existence of multiple degrees of freedom during inflation is suggested and simple single-field inflation models as origin of primordial perturbations should be ruled out. A number of models for isocurvature perturbations including the axion isocurvature model and the curvaton scenario predict that isocurvature perturbations can be highly non-Gaussian. While theoretical predictions are relatively well-studied, few attempts have been made to constrain isocurvature non-Gaussianity from actual data from cosmological observations. In this talk, I present a method to derive an optimal CMB constraint on the local-type non-Gaussianity in primordial isocurvature perturbations. Applying our method, I obtain current constraints from the WMAP 7-year data. Implications of our results for theoretical models including the axion and curvaton scenarios are also discussed.