Primordial perturbations from anisotropic inflation

by Dr Atsushi Naruko (Paris)

Tuesday 17 Sept 2013, 17:30 → 18:30 Europe/Berlin

TUM Physik Department 3343 (Universe)

In this talk, we study perturbations from an anisotropic inflation where inflation field couples with a vector field. In this model, vector field has the vacuum expectation value at background level which is homogeneous in space and hence the background spacetime becomes homogeneous but anisotropic different from usual homogeneous and isotropic background, FLRW universe. Interestingly, this model predicts statistically anisotropic power spectrum and it is customarily parametrized by g* where g* is defined by P (\vec{k}) = P (k) [1 + g* (\hat{k} \cdot \hat{v})] and \hat{v} denotes a preferred direction in space. By revisiting fluctuation on top of this anisotropic background, we find that the former prediction for g* will be revised and the constraint on background anisotropy during inflation from current observations can be much more loose.

 

The latter part of talk will be devoted to the study of the behavior of long wavelength (non-linear) fluctuations based on spatial gradient expansion approach. To begin with, by carefully looking at linear perturbation equations, we find that perturbation equations are exactly same as those for background under particular gauge (coordinate) choice. This fact indicates long wavelength fluctuations can be evaluated just by solving background equation as in \delta N formalism for FLRW universe. Finally we extend the analysis to non-linear order and investigate the behavior of non-linear fluctuation by constructing general solution.