The Aronsson equation for absolute minimizers of $L^{\infty }$-functionals associated with vector fields satisfying Hörmander's condition

Abstract

Given a Carnot-Carathéodory metric space $(R^n,d_{cc})$ generated by vector fields $\{X_i{\}}_{i=1}^m$ satisfying Hörmander's condition, we prove in theorem A that any absolute minimizer $u\in W^{1,\infty}_{\hbox{cc}}(\Om)$ to $F(v,\Om)=\sup_{x\in\Om}f(x,Xv(x))$ is a viscosity solution to the Aronsson equation (1.6), under suitable conditions on $f$. In particular, any AMLE is a viscosity solution to the subelliptic $\infty$-Laplacian equation (1.7). If the Carnot-Carathédory space is a Carnot group $\mathbf{G}$ and $f$ is independent of $x$-variable, we establish in theorem C the uniquness of viscosity solutions to the Aronsson equation (1.13) under suitable conditions on $f$. As a consequence, the uniqueness of both AMLE and viscosity solutions to the subelliptic $\infty$-Laplacian equation is established in $\mathbf{G}$

25 pages