2018/08/20 by Morbidelli, Daniele · 1 citation
#52A01 #53C17 #FOS: Mathematics #Metric Geometry (math.MG)
paper · doi:10.48550/arxiv.1808.06513
In the setting of step two Carnot groups, we show a "cone property" for horizontally convex sets. Namely we prove that, given a horizontally convex set C, a pair of points P∈ ∂ C and Q∈ int C, both belonging to a horizontal line ℓ, then an open truncated subRiemannian cone around ℓ and with vertex at P is contained in C. We apply our result to the problem of classification of horizontally monotone sets in Carnot groups. We are able to show that monotone sets in the direct product ℍ ×ℝ of the Heisenberg group with the real line have hyperplanes as boundaries.