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We generalize the Gamma $z$ calculus to study degenerate drift-diffusion processes, where $z$ stands for extra directions introduced into the degenerate system. Based on this calculus, we establish the sub-Riemannian Ricci curvature tensor and the associated curvature dimension bound for general sub-Riemannian manifolds. These results do not require the commutative iteration of Gamma and Gamma z operator and go beyond the step two condition. These allow us to analyze the convergence properties of degenerate drift-diffusion processes and prove the entropy dissipation rate and several functional inequalities in sub-Riemannian manifolds. Several examples are provided. In particular, we show the global in time convergence result for displacement group with a weighted volume on a compact region. The new Gamma $z$ calculus is motivated by optimal transport and density manifold. We embed the probability density space over sub-Riemannian manifold with the $L^2$ sub-Riemannian Wasserstein metric. We call it sub-Riemannian density manifold (SDM). We study the dynamical behavior of the degenerate Fokker-Planck equation as gradient flows in SDM. Our derivation builds an equivalence relation between Gamma z calculus and second-order calculus in SDM.
We derive sub-Riemannian Ricci curvature tensor for sub-Riemannian manifolds. We provide examples including the Heisenberg group, displacement group ($textbf{SE}(2)$), and Martinet sub-Riemannian structure with arbitrary weighted volumes, in which we
In a Riemannian manifold, the existence of a new connection is proved. In particular cases, this connection reduces to several symmetric, semi-symmetric and quarter-symmetric connections; even some of them are not introduced so far. We also find formula for curvature tensor of this new connection.
This note proves that any locally extremal non-self-conjugate geodesic loop in a Riemannian manifold is a closed geodesic. As a consequence, any complete and non-contractible Riemannian manifold with diverging injectivity radii along diverging sequen
We give a necessary condition on a geodesic in a Riemannian manifold that can run in some convex hypersurface. As a corollary we obtain peculiar properties that hold true for every convex set in any generic Riemannian manifold (M,g). For example, if
We relate the sub-Riemannian geometry on the group of rigid motions of the plane to `bicycling mathematics. We show that this geometrys geodesics correspond to bike paths whose front tracks are either non-inflectional Euler elasticae or straight line