Let F be a closed subset of
a 2-sphere S in E3. We define F to be tame if F lies on some tame 2-sphere in E3.
The sets F and S satisfy Property (∗,F,S) provided Bing’s Side Approximation
Theorem can be applied in such a way that the approximating 2-sphere S′ misses F
(that is, S ∩ S′ lies in a finite collection of disjoint small disks in S − F). In this
paper we show that Property (∗,F,S) implies that F is tame by establishing a
conjecture made by Gillman. Other properties which are equivalent to Property
(∗,F,S) are also given.
If F1,F2,⋯,Fn is a finite collection of closed subsets of S such that
Property (∗,Fi,S) holds for each i, then Property (∗,∑
Fi,S) also holds. We
use this result to show that if S is locally tame modulo ∑
Fi, then S is
tame.
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