A sub-Riemannian curvature-dimension inequality, volume doubling property and the Poincaré inequality

Abstract

Let $$\mathbb M $$ be a smooth connected manifold endowed with a smooth measure $$\mu $$ and a smooth locally subelliptic diffusion operator $$L$$ satisfying $$L1=0$$ , and which is symmetric with respect to $$\mu $$ . We show that if $$L$$ satisfies, with a non negative curvature parameter, the generalized curvature inequality introduced by the first and third named authors in http://arxiv.org/abs/1101.3590 , then the following properties hold: The key ingredient is the study of dimension dependent reverse log-Sobolev inequalities for the heat semigroup and corresponding non-linear reverse Harnack type inequalities. Our results apply in particular to all Sasakian manifolds whose horizontal Webster–Tanaka–Ricci curvature is nonnegative, all Carnot groups of step two, and to wide subclasses of principal bundles over Riemannian manifolds whose Ricci curvature is nonnegative.