Doppler Peaks in the Angular Power Spectrum of the Cosmic Microwave Background: A Fingerprint of Topological Defects

The Doppler peaks (Sacharov peaks) in the angular power spectrum of the cosmic microwave background anisotropies are due mainly to coherent oscillations in the baryon radiation plasma before recombination. Here we present a calculation of the Doppler peaks for perturbations induced by global textures and cold dark matter. We find that the height of the first Doppler peak is smaller than in standard cold dark matter models, and that its position is shifted to $\ell \sim 350$. We believe that our analysis can be easily extended to other types of global topological defects and general global scalar fields.