Constraints on the Topology of the Universe: Extension to General Geometries

TL;DR

This study searches for signs of a non-trivial universe topology using WMAP data, extending previous bounds, but finds no significant matched circle pairs, thus setting a new lower limit on the universe's size.

Contribution

It extends the search for cosmic topology to a wider range of geometries and refines the constraints using WMAP 7-year data, accounting for potential contamination.

Findings

No statistically significant matched circle pairs found.

Extended the lower limit on universe size to approximately 26 Gpc.

Identified anomalous regions likely due to contamination.

Abstract

We present an update to the search for a non-trivial topology of the universe by searching for matching circle pairs in the cosmic microwave background using the WMAP 7 year data release. We extend the exisiting bounds to encompass a wider range of possible topologies by searching for matching circle pairs with opening angles 10 degree < \alpha < 90 degree and separation angles 11 degree < \theta < 180 degree. The extended search reveal two small anomalous regions in the CMB sky. Numerous pairs of well-matched circles are found where both circles pass through one or the other of those regions. As this is not the signature of any known manifold, but is a likely consequence of contamination in those sky regions, we repeat the search excluding circle pairs where both pass through either of the two regions. We then find no statistically significant pairs of matched circles, and so no hints of a non-trivial topology. The absence of matched circles increases the lower limit on the length of the shortest closed null geodesic that self-intersects at our location in the universe (equivalently the injectivity radius at our location) to 98.5% of the diameter of the last scattering surface or approximately 26 Gpc. It extends the limit to any manifolds in which the intersecting arcs of said geodesic form an angle greater than 10^o.