MG12 - Talk detail
 

Back to previous page

 Participant 

Institution

Session

Talk

Abstract

Circles-in-the-sky searches and observable cosmic topology in flat and nearly flat3-manifolds

A (locally) homogeneous and isotropic Universe will have as spatial sections a constant-curvature 3-manifold. The determination of such manifold is, however, not unique. Depending on whether the spatial curvature is positive, negative or zero, there are infinite classes of topologically-distinct possibilities. The topology can, however, be determined through observations. Indeed, a detectable non-trivial topology implies the existence of pairs of matching circles of temperature fluctuations in CMB maps, the so-called circles in the sky (CitS). Searches for pairs of CitS, restricted to those which are nearly antipodal, have been undertaken, without success. For very small (but non-zero) curvatures (i.e., those compatible with typical inflationary models), we show that the aforementioned searches should in principle be sufficient to exclude a detectable manifolds with non-trivial topology for all but a tiny fraction of observers. However, for flat manifolds, in most cases there remains a substantial fraction of observers for which the searches for CitS already undertaken would be insufficiently inclusive. It is remarkable how such a slight variation in the value of curvature (effectively indistinguishable geometrically) can have such a drastic effect on the detectability of cosmic topology.

Back to previous page