Definable versions of theorems by Kirszbraun and Helly - Mathematics > LogicReport as inadecuate




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Abstract: Kirszbraun-s Theorem states that every Lipschitz map $S\to\mathbb R^n$, where$S\subseteq \mathbb R^m$, has an extension to a Lipschitz map $\mathbb R^m \to\mathbb R^n$ with the same Lipschitz constant. Its proof relies on Helly-sTheorem: every family of compact subsets of $\mathbb R^n$, having the propertythat each of its subfamilies consisting of at most $n+1$ sets share a commonpoint, has a non-empty intersection. We prove versions of these theorems validfor definable maps and sets in arbitrary definably complete expansions ofordered fields.



Author: Matthias Aschenbrenner, Andreas Fischer

Source: https://arxiv.org/







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