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arXiv · 1011.4145

A short and elementary proof of Hanner's theorem

Aasa Feragen
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Abstract

Hanner's theorem is a classical theorem in the theory of retracts and extensors in topological spaces, which states that a local ANE is an ANE. While Hanner's original proof of the theorem is quite simple for separable spaces, it is rather involved for the general case. We provide a proof which is not only short, but also elementary, relying only on well-known classical point-set topology.

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Aasa Feragen. 2010-11-18. A short and elementary proof of Hanner's theorem. https://arxiv.org/abs/1011.4145

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