Global Topological Defects and the Cosmic Microwave Background Anisotropies

ALEJANDRO GANGUI

General Relativity. Proceedings of the Forty Sixth SUSSP

Institute of Physics Publishing

Año: 1996; p. 408 - 408

We review recent work aimed at showing how global topological defects influence the shape of the angular power spectrum of the cosmic microwave background radiation on small scales. While Sachs--Wolfe fluctuations give the dominant contribution on angular scales larger than about a few degrees, on intermediate scales, $0.1^\circ \lsim \theta \lsim 2^\circ$, the main role is played by coherent oscillations in the baryon radiation plasma before recombination. In standard cosmological models these oscillations lead to the  `Doppler peaks' in the angular power spectrum. Inflation--based cold dark matter models predict the location of the first peak to be at approximately $220/\sqrt{\Omega_0}$, with a height which is a few times the amplitude at large scales. Here we focus on perturbations induced by global textures. We find  that  the first Doppler peak is reduced to an amplitude comparable to that of the Sachs-Wolfe contribution, and that it is shifted to $\ell\sim 350$. We briefly comment on the relation between our results and what open models predict. This report is based on joint work done in collaboration with R. Durrer and M. Sakellariadou.