The oscillation stability problem for the Urysohn sphere: A combinatorial approach.
Résumé
We study the oscillation stability problem for the Urysohn sphere, an analog of the distortion problem for $\ell _2$ in the context of the Urysohn space $\Ur$. In particular, we show that this problem reduces to a purely combinatorial problem involving a family of countable ultrahomogeneous metric spaces with finitely many distances.
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