ARE THERE ECHOES FROM THE PRE-BIG-BANG UNIVERSE? A SEARCH FOR LOW-VARIANCE CIRCLES IN THE COSMIC MICROWAVE BACKGROUND SKY.

In a recent analysis of Wilkinson Microwave Anisotropy Probe (WMAP) seven-year temperature maps, Gurzadyan and Penrose claim to find concentric circular patterns in the sky with anomalously low variances. These circles are presented as observational evidence for violent processes in a universe preceding our big bang as predicted by Penrose's Conformal Cyclic Cosmology. We reassess the statistical significance of the detection of the claimed concentric low-variance circles by comparing the WMAP data with Monte Carlo simulations of the cosmic microwave background (CMB) sky plus realistic modeling of WMAP's anisotropic noise. We find no anomaly in the variances compared with the ACDM cosmological model. The observed variances in the data are consistent with a Gaussian CMB sky as predicted by the inflationary cosmology model at better than 3σ. [ABSTRACT FROM AUTHOR]