Model independent early expansion history and dark energy

Abstract

We examine model independent constraints on the high redshift and prerecombination expansion history from upcoming cosmic microwave background observations, using a combination of principal component analysis and other techniques. This can be translated to model independent limits on early dark energy and the number of relativistic species Neff. Models such as scaling (Doran-Robbers), dark radiation (ΔNeff), and barotropic aether fall into distinct regions of eigenspace and can be easily distinguished from each other. Incoming CMB data will map the expansion history from z=0-105, achieving subpercent precision around recombination, and enable determination of the amount of early dark energy and valuable guidance to its nature. © 2012 American Physical Society.