In recent years interest has
been focused on the following two questions.
If G is an upper semi-continuous decomposition of E3 whose decomposition
space G′ is homeomorphic to E3, under what conditions can we conclude
that
(1) each element of G is point-like?
(2) there is a pseudo-isotopy F : E3 × [0,1] → E3 such that F|E3 × 0 is the
identity and F|E3 × 1 is equivalent to the projection map Π : E3 → G′?
An example of Bing of a decomposition of E3 into points, circles, and figure-eights
shows that some additional hypotheses must be inserted. The theorem presented here
gives such hypotheses, namely that the nondegenerate elements form the intersection
of a decreasing swquence of finite disjoint unions of cells-withhandles, and project
into a Cantor set.
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