Saturday, 10 February 2007

gn.general topology - What is enough to conclude that something is a CW complex (part II)?

A while ago I asked a question about recoqnizing CW complexes and got an extremely nice and concrete answer. However, I am still interested in a more general treatment of this and therefore pose the following closely related question:



Assume that XX is an n1n1 dimensional finite CW complex. and assume that X is given as a a set by the disjoint union of X and a single open cell e of dimension n. I.e. e is an open subspace of X homeomorphic to the open n disc (and of course X is homeomorphic to the complement). Also assume that X is compact Hausdorff.



Question: Are there some natural topological conditions to further put on X such that it follows that X is in fact a CW-complex with X as a sub-CW complex and e a single new cell?



Remark: The fact that X is such is equivalent to whether or not one can modify the homeomorphism of e to the open unit disc such that the inverse extends to the closed unit disc.



Ideas on answers (but I have no proofs or counter examples in any of the cases):



1) X is locally contractible.



2) X has the homotopy type of a CW complex.



3) The Combination of 1) and 2).



4) X is homeomorphic to a CW complex



The last is weird, but it is not clear to me that even this is enough!



Any ideas, counter examples, or references?

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