Principal Component Analysis of the Cosmic Microwave Background Anisotropies: Revealing The Tensor Degeneracy
George Efstathiou
Abstract
A principal component analysis of cosmic microwave background (CMB) anisotropy measurements is used to investigate degeneracies among cosmological parameters. The results show that a degeneracy with tensor modes -- the `tensor degeneracy' -- dominates uncertainties in estimates of the baryon and cold dark matter densities, omegab = Omegab h2, omegac = Ωc h2, from an analysis of CMB anisotropies alone. The principal component analysis agrees well with a maximum likelihood analysis of the observations, identifying the main degeneracy directions and providing an impression of the effective dimensionality of the parameter space.
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