CMB polarization can constrain cosmology better than CMB temperature

We demonstrate that for a cosmic variance limited experiment, cosmic microwave background (CMB) E polarization alone places stronger constraints on cosmological parameters than CMB temperature. For example, we show that C-l(EE) can constrain parameters better than C-l(TT) by up to a factor 2.8 when a multipole range of l = 30-2500 is considered. We expose the physical effects at play behind this remarkable result and study how it depends on the multipole range included in the analysis. In most relevant cases, C-l(TE) or C-l(EE) surpass the C-l(TT)-based cosmological constraints. This result is important as the small-scale astrophysical foregrounds are expected to have a much reduced impact on polarization, thus opening the possibility of building cleaner and more stringent constraints of the.CDM model. This is relevant especially for proposed future CMB satellite missions, such as CORE or PRISM, that are designed to be cosmic variance limited in polarization till very large multipoles. We perform the same analysis for a Planck-like experiment, and conclude that even in this case C-l(TE) alone should determine the constraint on Omega(c)h(2) better than C(l)(TT)by similar to 15%, while determining Omega(b)h(2), n(s) and theta with comparable accuracy. Finally, we explore a few classical extensions of the Lambda CDM model and show again that CMB polarization alone provides more stringent constraints than CMB temperature in the case of a cosmic variance limited experiment.