
Journal of Convex Analysis 26 (2019), No. 3, 967989 Copyright Heldermann Verlag 2019 On the HConeFunctions for HConvex Sets Andrea Calogero Dip. di Matematica e Applicazioni, Universitá di MilanoBicocca, 20125 Milano, Italy andrea.calogero@unimib.it Rita Pini Dip. di Matematica e Applicazioni, Universitá di MilanoBicocca, 20125 Milano, Italy rita.pini@unimib.it [Abstractpdf] \def\H{{\mathbb H}} Given a compact and Hconvex subset $K$ of the Heisenberg group $\H$, with the origin $e$ in its interior, we are interested in finding a homogeneous Hconvex function $f$ such that $f(e)=0$ and $f\bigl_{\partial K}=1$; we will call this function $f$ the $\H$conefunction of vertex $e$ and base $\partial K$. While the equivalent version of this problem in the Euclidean framework has an easy solution, in our context this investigation turns out to be quite entangled, and the problem can be unsolvable. The approach we follow makes use of an extension of the notion of convex family introduced by Fenchel. We provide the precise, even if awkward, condition required to $K$ so that $\partial K$ is the base of an $\H$conefunction of vertex $e.$ Via a suitable employment of this condition, we prove two interesting binding constraints on the shape of the set $K,$ together with several examples. Keywords: Heisenberg group, Hconvexity, convex families, conefunctions. MSC: 26B25; 53C17, 22E30, 22E25 [ Fulltextpdf (189 KB)] for subscribers only. 