Sub-Laplacian generalized curvature dimension inequalities on Riemannian foliations

TL;DR

This paper develops a comprehensive Bochner and Bakry-Emery calculus framework for horizontal Laplacians on Riemannian foliations, leading to generalized curvature inequalities and geometric analysis results without restrictive assumptions.

Contribution

It introduces a new Bochner theory and curvature dimension inequalities for horizontal Laplacians on Riemannian foliations without bundle-like or minimality assumptions.

Findings

Derived explicit Bochner formulas involving Ricci curvature, torsion, and mean curvature.

Established generalized curvature dimension inequalities extending sub-Riemannian results.

Obtained geometric and analytic applications such as comparison theorems, eigenvalue estimates, and heat semigroup regularity.

Abstract

We develop a Bochner theory and Bakry-Emery calculus for horizontal Laplacians associated with general Riemannian foliations. No bundle-like assumption on the metric, nor any total geodesicity or minimality condition on the leaves is imposed. Using a metric connection adapted to the horizontal-vertical splitting, we derive explicit Bochner formulas for the horizontal Laplacian acting on horizontal and vertical gradients, as well as a unified identity for the full gradient. These formulas involve horizontal Ricci curvature, torsion and vertical mean curvature terms intrinsic to the foliated structure. From these identities, we establish generalized curvature dimension inequalities, extending earlier results in sub-Riemannian geometry. As applications, we obtain horizontal Laplacian comparison theorems, Bonnet-Myers type compactness results with explicit diameter bounds, stochastic completeness, first eigenvalue estimates and gradient and regularization estimates for the horizontal heat semigroup. The framework applies, in particular, to contact manifolds and Carnot groups of arbitrary step.