Title of article :
When does the Fell topology on a hyperspace of closed sets coincide with the meet of the upper Kuratowski and the lower Vietoris topologies?
Author/Authors :
Nogura، نويسنده , , Tsugunori and Shakhmatov، نويسنده , , Dmitri، نويسنده ,
Issue Information :
دوماهنامه با شماره پیاپی سال 1996
Abstract :
For a given topological space X we consider two topologies on the hyperspace F(X) of all closed subsets of X. The Fell topology TF on F(X) is generated by the family {OVK: V is open in X and K ⊆ X is compact} as a subbase, where OVK = {F ϵ F(X): F ∩ V ≠ Ø and F ∩ K = Ø}. The topology TF is always compact, regardless of the space X. The Kuratowski topology TK is the smallest topology on F(X) which contains both the lower Vietoris topology TlV, generated by the family {{F ϵ F(X): F \ Φ ≠ Ø}: Φ ϵ F(X)} as a subbase, and the upper Kuratowski topology TuK, which is the strongest topology on F(X) such that upper KuratowskiPainlevé convergence of an arbitrary net of closed subsets of X to some closed set A implies that the same net, considered as a net of points of the topological space (F(X), TuK), converges in this space to the point A. [Recall that a net 〈Aλ〉λ ϵ Λ ⊆ F(X) upper Kuratowski-Painlevé converges to A if ∩{∪{Aμ: μ ⩾ λ}: λ ϵ Λ} ⊆ A.] The inclusion TF ⊆ TK holds for an arbitrary space X, while the equation TF = TK is equivalent to consonance of X, the notion recently introduced by Dolecki, Greco and Lechicki. These three authors showed that complete metric spaces are consonant. In our paper we give an example of a metric space with the Baire property which is not consonant. We also demonstrate that consonance is a delicate property by providing an example of two consonant spaces X and Y such that their disjoint union X ⊕ Y is not consonant. In particular, locally consonant spaces need not be consonant.
Keywords :
Topologization of convergence , Metric space , Hyperspace , Kuratowski topology , Upper Kuratowski topology , Fell topology , Upper Kuratowski-Painlevé convergence , Kuratowski-Painlevé convergence
Journal title :
Topology and its Applications
Journal title :
Topology and its Applications