A search for concentric circles in the 7-year WMAP temperature sky maps
  In a recent analysis of the 7-year WMAP temperature sky maps, Gurzadyan and
Penrose claim to find evidence for violent pre-Big Bang activity in the form of
concentric low-variance circles at high statistical significance. In this
paper, we perform an independent search for such concentric low-variance
circles, employing both chi^2 statistics and matched filters, and compare the
results obtained from the 7-year WMAP temperature sky maps with those obtained
from LCDM simulations. Our main findings are the following: We do reproduce the
claimed ring structures observed in the WMAP data as presented by Gurzadyan and
Penrose, thereby verifying their computational procedures. However, the results
from our simulations do not agree with those presented by Gurzadyan and
Penrose. On the contrary we obtain a substantially larger variance in our
simulations, to the extent that the observed WMAP sky maps are fully consistent
with the LCDM model as measured by these statistics.
