Cosmic microwave background anisotropies

Restricted Access.Anisotropies in the Cosmic Microwave Background are a probe of the spectrum of density perturbations in the early universe and of the astrophysical and dynamical evolution that caused the formation of galaxies and the present day observed structure in the universe. Theory of the coupling of the perturbations to the radiation predicts characteristic features in the spectrum of the anisotropies. Experiments measure the anisotropy power as viewed through spectral windows. We review the current status, of the predictions of the anisotropy power spectrum and the constraints on the spectrum from observations