问题及解答

AHS (Alexander Horned Sphere)

J. W. Alexander 构造了一个单连通曲面, 其(外面)所围区域非单连通. 文章很短, 见 [1].

具体的构造如下:

References:

[1]  J. W. Alexander, Proceedings of the National Academy of Sciences of the United States of America, Jan. 15, 1924, Vol. 10, No. 1 (Jan. 15, 1924), pp. 8--10.