Wild sphere

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A closed manifold in Euclidean three-space obtained by a wild imbedding of the sphere in . Thus, a wild sphere is the sum of two discs with a common boundary, which is a wild knot. The first example of a wild sphere is the so-called "horned sphere of Alexanderhorned sphere" or Alexander sphere (Fig. a); it bounds a domain which is not homeomorphic to (in the figure this is the interior of the cylinder without any interlinking handles and points forming their boundary). Fig. b shows a wild sphere in which the exterior domain alone is not homeomorphic to .

Figure: w097990a

Figure: w097990b


[1] L.V. Keldysh, "Topological imbeddings in Euclidean space" Proc. Steklov Inst. Math. , 81 (1968) Trudy Mat. Inst. Akad. Nauk. SSSR , 81 (1966)



[a1] R.H. Bing, "The geometric topology of -manifolds" , Amer. Math. Soc. (1983)
[a2] E.E. Moise, "Geometric topology in dimensions 2 and 3" , Springer (1977)
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Wild sphere. Encyclopedia of Mathematics. URL:
This article was adapted from an original article by M.I. Voitsekhovskii (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article