Abstract. We prove a sub-Riemannian maximum principle for semicontinuous functions. We apply this principle to Carnot groups to provide a "sub-Riemannian" proof of the uniqueness of viscosity infinite harmonic functions. This is an alternate method of proof from the one found in [15]. We also establish the equivalence of weak solutions and viscosity solutions to the p-Laplace equation. This result extends the author's previous work in the Heisenberg group [3, 4].
Calculus on Carnot groupsWe begin by denoting an arbitrary Carnot group in R N by G and its corresponding Lie Algebra by g. Recall that g is nilpotent and stratified, resulting in the decompositionfor appropriate vector spaces that satisfy the Lie bracket relation [V 1 , V j ] = V 1+j . The Lie Algebra g is associated with the group G via the exponential map exp : g → G.Since this map is a diffeomorphism, we can choose a basis for g so that it is the identity map. Denote this basis byWe endow g with an inner product ·, · and related norm · so that this basis is orthonormal. Clearly, the Riemannian dimension of g (and so G) is N = n 1 +n 2 +n 3 . However, we will also consider the homogeneous dimension of G, denoted Q, which is given by