ACP Seminar (Astronomy - Cosmology - Particle Physics)

Speaker: Ryo Namba (Minnesota)
Title: Characteristic signatures in non-gaussianity and statistical anisotropy from vector fields during inflation
Date (JST): Thu, Sep 06, 2012, 15:30 - 16:30
Place: Seminar Room A
Related File: 751.pdf
Abstract: The simplest realizations of inflation are consistent with the current observational data, and predict statistically isotropic spectrum and undetectable non-gaussianity of the cosmic microwave background (CMB) fluctuations. However, there is a large ongoing activity, both experimental and theoretical, to search for finer signatures in the CMB in order to reveal the underlying physics of the very early universe. Such efforts are particularly relevant at present, as the data on cosmology from the Planck satellite will be released within one year. In this talk we study some characteristic signatures arising from a dilation-like coupling between a vector field and a scalar inflaton. In the first part of the talk we show that, for a massless vector field, this coupling can result in observable non-gaussianity, even in the conventional regime where inflation is supported by a single scalar slowly rolling on a smooth potential. In the squeezed limit, the resulting bispectrum is close to the local one, but it shows a sizable and characteristic quadrupolar dependence on the angle between the shorter and the larger modes in the correlation. In the second part of the talk we compute the statistical anisotropy for a model of vector curvaton in which the inflation also provides a mass term for the vector.