The circles-in-the-sky signature for three spherical universes

Abstract

The mysteriously low cosmic microwave background (CMB) power on the largest scales might point to a Universe which consists of a multi-connected space. In addition to a suppression of large-scale power, a multi-connected space can be revealed by its circles-in-the-sky signature. In this paper, a detailed search for this signature is carried out for those three homogeneous multi-connected spherical space forms that lead to the smallest large-scale power. A simultaneous search for all occurring paired circles is made using filtered CMB sky maps which enhance the ordinary Sachs-Wolfe contribution. A marginal hint is found for the right-handed Poincaré dodecahedron at and for the right-handed binary tetrahedral space at. However, due to the complicated noise and foreground structure of the available microwave sky maps, we cannot draw firm conclusions from our findings. © 2006 RAS.