Covariant Calculus and Hamiltonian Flows for Nonlocal Wasserstein Metrics

Abstract

In this paper, we study nonlocal metrics on smooth positive probability densities on a closed manifold, induced by symmetric jump kernels and density-dependent mobilities. First, we introduce the density-variation operator to express the density derivatives of the Dirichlet form and kinetic energy. Second, we construct density and velocity-field representations of the tangent space and prove their isometric equivalence. We use the generator's pseudoinverse to derive Levi-Civita connections and covariant differentials in both representations. Third, we establish mechanical Hamiltonian dynamics in both tangent representations; an action principle and Legendre duality identify the Hamilton--Jacobi and covariant Newton equations; smooth negative gradient flows admit a zero-energy Hamiltonian lift. Entropy diffusion, nonlocal mean-field equations, Keller--Segel dynamics, and a nonlocal Vlasov equation illustrate the resulting calculus. For geometric-mean mobility, the Hopf--Cole transformation of the nonlocal Schrödinger bridge system and the Madelung transformation of the nonlocal Schrödinger equation yield hyperbolic and trigonometric phase energies, respectively. At zero momentum, both recover the metric kinetic energy to second order.