We analyse the anisotropy of the cosmic microwave background (CMB) in hyperbolic universes possessing a non-trivial topology with a fundamental cell having an infinitely long horn. The aim of this paperis twofold. On the one hand, we show that the horned topology does not lead to a flat spot in the CMB sky maps in the direction of the horn asstated in the literature. On the other, we demonstrate that a horned topology having a finite volume could explain the suppression of the lower multipoles in the CMB anisotropy as observed by COBE and WMAP.
Aurich, R., Lustig, S., Steiner, F., & Then, H. (2004). Hyperbolic universes with a horned topology and the cosmic microwave background anisotropy. Classical and Quantum Gravity, 21(21), 4901-4925. https://doi.org/10.1088/0264-9381/21/21/010