CH-manifold
This article defines a property that makes sense for a Riemannian metric over a differential manifold
Definition
A CH-manifold or Cartan-Hadamard manifold is a Riemannian manifold that is simply connected, complete, and has nonpositive sectional curvature. By the Cartan-Hadamard theorem, any CH-manifold is diffeomorphic to some real Euclidean space.