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Sets of probability measures and convex combination spaces
Proceedings of the Thirteenth International Symposium on Imprecise Probability: Theories and Applications, PMLR 215:3-10, 2023.
Abstract
The Wasserstein distances between probability distributions are an important tool in modern probability theory which has been generalized to sets of probability distributions. We will show that the (generalized) $L^1$-Wasserstein metric, with the operations of convolution and rescaling, fits in the abstract framework of convex combination spaces: nonlinear metric spaces preserving some of the nice properties of a normed space but accomodating other unusual behaviours. For instance, unlike in a linear space, a singleton $\{P\}$ is typically not convex (it is so only if $P$ is degenerate). Also, some theorems for convex combination spaces are applied to this setting.