The cosmic microwave background and the shape of the Universe
Seminar Room 1, Newton Institute
The anisotropy of the cosmic microwave background (CMB) is analysed in nearly flat hyperbolic universes possessing a non-trivial topology with a fundamental cell which is stretched out into an infinitely long horn. It is shown that the horned topology does not lead to a flat spot in the CMB sky maps in the direction of the horn as predicted by Levin, Barrow, Bunn, and Silk.Two particular topologies are discussed in detail: the Sokolov-Starobinsky model having an infinite spatial volume, and the Picard orbifold which has a finite volume. It is demonstrated that the recent observations of the "Wilkinson Microwave Anisotropy Probe" (WMAP) hint that our Universe may be shaped like the Picard space.