Hanner定理的一个简单证明
A short and elementary proof of Hanner's theorem
摘要：
Hanner定理是拓扑空间中收缩子和扩张子理论中的一个经典定理，它指出局部ANE是ANE。虽然汉纳原来的证明定理是相当简单的可分空间，它是相当涉及的一般情况下。我们提供了一个证明，这不仅是短的，而且是小学，只依赖于著名的经典点集拓扑。
英文摘要：
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.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
