Calculus of Variations and Geometric Measure Theory

V. Franceschi - R. Monti - A. Righini - M. Sigalotti

The isoperimetric problem for regular and crystalline norms in $\mathbb H^1$

created by franceschi on 22 Jul 2020
modified on 22 Mar 2023


Published Paper

Inserted: 22 jul 2020
Last Updated: 22 mar 2023

Journal: Journal of Geometric Analysis
Year: 2020
Doi: 10.1007/s12220-022-01045-4

ArXiv: 2007.11384 PDF


We study the isoperimetric problem for anisotropic left-invariant perimeter measures on $\mathbb R^3$, endowed with the Heisenberg group structure. The perimeter is associated with a left-invariant norm $\phi$ on the horizontal distribution. We first prove a representation formula for the $\phi$-perimeter of regular sets and, assuming some regularity on $\phi$ and on its dual norm $\phi^*$, we deduce a foliation property by sub-Finsler geodesics of $C^2$-smooth surfaces with constant $\phi$-curvature. We then prove that the characteristic set of $C^2$-smooth surfaces that are locally extremal for the isoperimetric problem is made of isolated points and horizontal curves satisfying a suitable differential equation. Based on such a characterization, we characterize $C^2$-smooth $\phi$-isoperimetric sets as the sub-Finsler analogue of Pansu's bubbles. We also show, under suitable regularity properties on $\phi$, that such sub-Finsler candidate isoperimetric sets are indeed $\C^2$-smooth. By an approximation procedure, we finally prove a conditional minimality property for the candidate solutions in the general case (including the case where $\phi$ is crystalline).

Keywords: Heisenberg group, anisotropic perimeter, isoperimetric problem, sub-Finsler geometry, Wulff shapes, Pansu's bubbles