2011-07-04

Emir Gumrukcuoglu ( http://homepages.spa.umn.edu/~ahmet/index.html )

TITLE: Primordial anisotropy as a source of stastical isotropy breaking

ABSTRACT:



Motivated by the signatures of broken statistical isotropy in the Cosmic Microwave Background (CMB), the linear computation of the primordial perturbations has been extended to Bianchi-I backgrounds in the last few years. Constructions in these backgrounds generically give an angle dependent scalar power spectrum, which may provide an early cosmological explanation of the feature observed in the CMB. Additionally, nonzero cross corelation between tensor and scalar modes, two gravity wave polarization evolving differently are among the typical consequences of these scenarios.



In this talk, I will review two different approaches to anisotropic model building. The first approach considers inflation in a geometry that is anisotropic as an initial condition. In these models, the universe is isotropized within a Hubble time, and the duration of inflation needs to be fine tuned for nonstandard signatures. The second approach relies on other fields to source the anisotropy, thus evading the cosmic no-hair conjecture and attain a sustainable anisotropy under certain conditions. Typically, the extra source is taken to be a vector field with a coupling (and mass, if massive) that are modulated by the inflaton field. These scenarios have very distinct phenomenological signatures which may help us differentiate among different models of (anisotropic) inflation.