Illinois Journal of Math.
Inserted: 15 jul 2016
Last Updated: 23 jul 2017
Year: 2016
Abstract:
A set is porous if each point sees relatively large holes in the set on arbitrarily small scales. We show that sets porous with respect to the Carnot-Carath\'eodory distance are much smaller than measure zero sets and are not comparable with sets porous with respect to the Euclidean distance. We construct a Lipschitz function which is Pansu differentiable at no point of a given sigma-porous set and show preimages of open sets under the horizontal gradient are far from being porous.
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