English

A short and elementary proof of Hanner's theorem

General Topology 2010-11-19 v1 Geometric Topology

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.

Keywords

Cite

@article{arxiv.1011.4145,
  title  = {A short and elementary proof of Hanner's theorem},
  author = {Aasa Feragen},
  journal= {arXiv preprint arXiv:1011.4145},
  year   = {2010}
}

Comments

2 pages

R2 v1 2026-06-21T16:45:34.283Z