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yoshito-ishiki-math/lean-scottish-book-155

Yoshito Ishiki

Palomar Registrypalomar/PALOMAR-2026-08-31-000008Aug 31, 2026math.FAscore 0

A Lean proof that there are real Banach spaces X and Y and a bijection U from X to Y which preserves every pairwise distance on every closed ball of radius one quarter while failing to be a global isometry. This gives a counterexample to Scottish Book Problem 155.

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