Orbifold line topology and the cosmic microwave background

Abstract

We extend our study of a universe with a non-classical stringy topology, and consider an orbifold line topology, Bbb R × Bbb R²/Bbb 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.