Model Independent Early Expansion History and Dark Energy

We examine model independent constraints on the high redshift and prerecombination expansion history from 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 $N_{\mathrm{e}\mathrm{f}\mathrm{f}}$. Models such as scaling (Doran-Robbers), dark radiation ($\mathrm{\Delta }{N}_{\mathrm{e}\mathrm{f}\mathrm{f}}$), 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 $z=0$–${10}^5$, achieving subpercent precision around recombination, and enable determination of the amount of early dark energy and valuable guidance to its nature.