Transport information geometry: Riemannian calculus on probability simplex

Information Geometry - Tập 5 - Trang 161-207 - 2021
Wuchen Li1
1Department of Mathematics, University of South Carolina, Columbia, USA

Tóm tắt

We formulate the Riemannian calculus of the probability set embedded with $$L^2$$ -Wasserstein metric. This is an initial work of transport information geometry. Our investigation starts with the probability simplex (probability manifold) supported on vertices of a finite graph. The main idea is to embed the probability manifold as a submanifold of the positive measure space with a weighted graph Laplacian operator. By this viewpoint, we establish torsion–free Christoffel symbols, Levi–Civita connections, curvature tensors and volume forms in the probability manifold by Euclidean coordinates. As a consequence, the Jacobi equation, Laplace-Beltrami, Hessian operators and diffusion processes on the probability manifold are derived. These geometric computations are also provided in the infinite-dimensional density space (density manifold) supported on a finite-dimensional manifold. In particular, we present an identity connecting among Baker–Émery $$\Gamma _2$$ operator (carré du champ itéré), Fisher–Rao metric and optimal transport metric. Several examples are demonstrated.

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