Jeff Zheng (UR ’11) and I just submitted a paper for publication in Physical Review D. It’s also on the preprint arXiv. The point of the paper is to examine possible explanations for a couple of the supposed “anomalies” in the cosmic microwave background radiation on large angular scales. These anomalies are unexpected patterns in the microwave background. For instance, fluctuations corresponding to waves with different wavelengths on the sky should be completely unrelated to each other, but a couple of the largest observable wave patterns point in almost exactly the same direction as each other. In addition, one half of the sky seems to have slightly larger-amplitude fluctuations than the other half.
It’s hard to know how seriously to take these puzzles: human beings are very good at seeing patterns, even when those patterns are just due to chance. That might be all that’s going on here, but in our paper we tentatively adopt the point of view that the patterns are meaningful, and then assess some possible theories for what might have caused them. We show that some alternative theories do provide a better fit to the data, but only slightly better, and we calculate (using a piece of machinery known as Bayesian evidence) that that improvement in fit is too small to be regarded as significant evidence in favor of the alternative theories.