The search for the topology of the Universe has only just begun

Abstract

The topology of the Universe is not directly constrained by general relativity, and quantum mechanics may indeed prefer the creation of small Universes with nontrivial topologies. Large-scale cosmological measurements have shown no direct evidence of the patterns that would be induced in these cases, and the shortest distance around the Universe through us is unlikely to be much larger than the horizon diameter if microwave background anomalies are due to cosmic topology. I will discuss observational constraints from the lack of matched temperature circles in the microwave background which nonetheless leave many possibilities for such topologies, and further possibilities for their detection through large-scale correlations. I will also show that the large scale structure of space, rather than parity-violating microphysics, induces CMB parity violation in some topologies. Searches or topology signatures in observational data over the large space of possible topologies pose a formidable computational challenge, but is crucial for our understanding of the Universe.

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