Bi-Lipschitz embeddings of the space of unordered $m$-tuples with a partial transportation metric
Let $Ω\subset \mathbb{R}^n$ be non-empty, open and proper. Consider $Wb(Ω)$, the space of finite Borel measures on $Ω$ equipped with the partial transportation metric introduced by Figalli and Gigli that allows the creation and destruction of mass on $\partial Ω$. Equivalently, we show that $Wb(Ω)$ is isometric to a subset of all Borel measures with the ordinary Wasserstein distance, on the one point completion of $Ω$ equipped with the shortcut metric \[δ(x,y)= \min\{\|x-y\|, \operatorname{dist}(x,\partial Ω)+\operatorname{dist}(y,\partialΩ)\}.\] In this article we construct bi-Lipschitz embeddings of the set of unordered $m$-tuples in $Wb(Ω)$ into Hilbert space. This generalises Almgren's bi-Lipschitz embedding theorem to the setting of optimal partial transport.