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Characterizing metric spaces whose hyperspaces are homeomorphic to ℓ₂

T. Banakh, R. Voytsitskyy (2008)

Colloquium Mathematicae

It is shown that the hyperspace C l d H ( X ) (resp. B d d H ( X ) ) of non-empty closed (resp. closed and bounded) subsets of a metric space (X,d) is homeomorphic to ℓ₂ if and only if the completion X̅ of X is connected and locally connected, X is topologically complete and nowhere locally compact, and each subset (resp. each bounded subset) of X is totally bounded.

Extending Maps in Hilbert Manifolds

Piotr Niemiec (2012)

Bulletin of the Polish Academy of Sciences. Mathematics

Certain results on extending maps taking values in Hilbert manifolds by maps which are close to being embeddings are presented. Sufficient conditions on a map under which it is extendable by an embedding are given. In particular, it is shown that if X is a completely metrizable space of topological weight not greater than α ≥ ℵ₀, A is a closed set in X and f: X → M is a map into a manifold M modelled on a Hilbert space of dimension α such that f ( X A ) f ( A ) ¯ = , then for every open cover of M there is a map g:...

Extension properties of Stone-Čech coronas and proper absolute extensors

A. Chigogidze (2013)

Fundamenta Mathematicae

We characterize, in terms of X, the extensional dimension of the Stone-Čech corona βX∖X of a locally compact and Lindelöf space X. The non-Lindelöf case is also settled in terms of extending proper maps with values in I τ L , where L is a finite complex. Further, for a finite complex L, an uncountable cardinal τ and a Z τ -set X in the Tikhonov cube I τ we find a necessary and sufficient condition, in terms of I τ X , for X to be in the class AE([L]). We also introduce a concept of a proper absolute extensor and...

F σ -absorbing sequences in hyperspaces of subcontinua

Helma Gladdines (1993)

Commentationes Mathematicae Universitatis Carolinae

Let 𝒟 denote a true dimension function, i.e., a dimension function such that 𝒟 ( n ) = n for all n . For a space X , we denote the hyperspace consisting of all compact connected, non-empty subsets by C ( X ) . If X is a countable infinite product of non-degenerate Peano continua, then the sequence ( 𝒟 n ( C ( X ) ) ) n = 2 is F σ -absorbing in C ( X ) . As a consequence, there is a homeomorphism h : C ( X ) Q such that for all n , h [ { A C ( X ) : 𝒟 ( A ) n + 1 } ] = B n × Q × Q × , where B denotes the pseudo boundary of the Hilbert cube Q . It follows that if X is a countable infinite product of non-degenerate...

Functor of extension in Hilbert cube and Hilbert space

Piotr Niemiec (2014)

Open Mathematics

It is shown that if Ω = Q or Ω = ℓ 2, then there exists a functor of extension of maps between Z-sets in Ω to mappings of Ω into itself. This functor transforms homeomorphisms into homeomorphisms, thus giving a functorial setting to a well-known theorem of Anderson [Anderson R.D., On topological infinite deficiency, Michigan Math. J., 1967, 14, 365–383]. It also preserves convergence of sequences of mappings, both pointwise and uniform on compact sets, and supremum distances as well as uniform continuity,...

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