No evidence for anomalously low variance circles on the sky

TL;DR

This paper critically examines claims of anomalously low variance circles in the CMB, demonstrating that such features are consistent with standard Gaussian fluctuations and do not provide evidence for new physics.

Contribution

The authors replicate previous analyses and show that the claimed low variance circles are expected features of Gaussian CMB simulations, challenging earlier interpretations.

Findings

Low variance circles are consistent with Gaussian CMB fluctuations

No evidence found for pre-Big Bang phenomena in the CMB

Claims of anomalous structures are explained by standard cosmological models

Abstract

In a recent paper, Gurzadyan & Penrose claim to have found directions on the sky centred on which are circles of anomalously low variance in the cosmic microwave background (CMB). These features are presented as evidence for a particular picture of the very early Universe. We attempted to repeat the analysis of these authors, and we can indeed confirm that such variations do exist in the temperature variance for annuli around points in the data. However, we find that this variation is entirely expected in a sky which contains the usual CMB anisotropies. In other words, properly simulated Gaussian CMB data contain just the sorts of variations claimed. Gurzadyan & Penrose have not found evidence for pre-Big Bang phenomena, but have simply re-discovered that the CMB contains structure.