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The space of ANR’s in n

Tadeusz DobrowolskiLeonard Rubin — 1994

Fundamenta Mathematicae

The hyperspaces A N R ( n ) and A R ( n ) in 2 n ( n 3 ) consisting respectively of all compact absolute neighborhood retracts and all compact absolute retracts are studied. It is shown that both have the Borel type of absolute G δ σ δ -spaces and that, indeed, they are not F σ δ σ -spaces. The main result is that A N R ( n ) is an absorber for the class of all absolute G δ σ δ -spaces and is therefore homeomorphic to the standard model space Ω 3 of this class.

Inverse Sequences and Absolute Co-Extensors

Ivan IvanšićLeonard R. Rubin — 2007

Bulletin of the Polish Academy of Sciences. Mathematics

Suppose that K is a CW-complex, X is an inverse sequence of stratifiable spaces, and X = limX. Using the concept of semi-sequence, we provide a necessary and sufficient condition for X to be an absolute co-extensor for K in terms of the inverse sequence X and without recourse to any specific properties of its limit. To say that X is an absolute co-extensor for K is the same as saying that K is an absolute extensor for X, i.e., that each map f:A → K from a closed subset A of X extends to a map F:X...

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