Is the Universe Normal? Constraining Scale-Dependent Primordial Non-Gaussianity.

Abstract

Non-Gaussianity is a potentially powerful probe of inflationary physics in the very early universe. The detection of significant primordial non-Gaussianity would be a serious challenge to the simplest models of inflation. Models with non-Gaussianity that varies with spatial scale are of particular interest; this is generically predicted by single-field inflationary models with interactions and most multi-field models. In this dissertation, I focus on a scale-dependent generalization of the local model of non- Gaussianity, in which the parameter quantifying departures from Gaussianity, fNL, is promoted to a function of scale, fNL(k). I forecast constraints on fNL(k) expected from upcoming large-scale structure and cosmic microwave background data. Finally, I use the WMAP7 data to obtain the first constraints on the scale-dependence of non-Gaussianity.