A GEOMETRIC STUDY OF WASSERSTEIN SPACES: HADAMARD SPACES
Abstract
Optimal transport enables one to construct a metric on the set of (sufficiently small at infinity) probability measures on any (not too wild) metric space X, called its Wasserstein space .
In this paper we investigate the geometry of when X is a Hadamard space, by which we mean that X has globally non-positive sectional curvature and is locally compact. Although it is known that, except in the case of the line,
is not non-positively curved, our results show that
have large-scale properties reminiscent of that of X. In particular we define a geodesic boundary for
that enables us to prove a non-embeddablity result: if X has the visibility property, then the Euclidean plane does not admit any isometric embedding in
.