Searching for Extremal Spots in Planck Lensing Maps
  A great deal of attention has been given to the so-called Cold Spot in maps
of the cosmic microwave background (CMB) temperature. We present a similar
analysis, searching for extremal spots in the CMB lensing convergence and
lensing potential maps from the Planck 2018 data release. We perform a
multi-scale and multi-filter analysis using the first three members of the
Mexican-hat wavelet family to search for extremal features of different shapes
and sizes. Although an initial analysis appears to show the existence of some
extremal spots at scales below about 5 degree, we conclude, after marginalising
over all scales and filters, that no significant features are detected in the
lensing maps. We conclude that in terms of maxima and minima of various sizes,
the lensing data have similar statistical properties to Gaussian simulations.
