Orbifold Line Topology and the Cosmic Microwave Background

TL;DR

This paper investigates the potential cosmic microwave background signatures of an orbifold line universe topology, finding no conclusive evidence for such topology in current WMAP and Planck data.

Contribution

It extends the study of non-classical stringy topologies to orbifold line models and constrains their parameters using CMB data.

Findings

No evidence for orbifold line topology with p up to 10 in WMAP data.

The peak at p=8 in WMAP data is not supported by Planck data.

Orbifold line topology with p=8 is ruled out by current observations.

Abstract

We extend our study of a universe with a non-classical stringy topology, and consider an orbifold line topology, $\mathbb{R}\times\mathbb{R}^2/\mathbb{Z}_p$. This topology has a fixed line and identifies each point in space with $p-1$ other points. An observable imprint of an orbifold line on the CMB is the appearance of up to $(p-1)/2$ pairs of matching circles. Searching the WMAP data for matching circles, we can rule out an orbifold line topology with $p$ up to 10, except for $p=8$. While the significance of the peak at $p=8$ varies between data releases of WMAP, it does not appear in Planck data, enabling us to rule out $p=8$ as well.