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On theorems of Pu & Pu and Grande

Aleksander Maliszewski (1996)

Mathematica Bohemica

Given a finite family of cliquish functions, , we can find a Lebesgue function α such that f + α is Darboux and quasi-continuous for every f . This theorem is a generalization both of the theorem by H. W. Pu H. H. Pu and of the theorem by Z. Grande.

On weak forms of preopen and preclosed functions

Miguel Caldas, Govindappa Navalagi (2004)

Archivum Mathematicum

In this paper we introduce two classes of functions called weakly preopen and weakly preclosed functions as generalization of weak openness and weak closedness due to [26] and [27] respectively. We obtain their characterizations, their basic properties and their relationshisps with other types of functions between topological spaces.

On weakly Gibson F σ -measurable mappings

Olena Karlova, Volodymyr Mykhaylyuk (2013)

Colloquium Mathematicae

A function f: X → Y between topological spaces is said to be a weakly Gibson function if f ( Ū ) f ( U ) ¯ for any open connected set U ⊆ X. We prove that if X is a locally connected hereditarily Baire space and Y is a T₁-space then an F σ -measurable mapping f: X → Y is weakly Gibson if and only if for any connected set C ⊆ X with dense connected interior the image f(C) is connected. Moreover, we show that each weakly Gibson F σ -measurable mapping f: ℝⁿ → Y, where Y is a T₁-space, has a connected graph.

On α -continuous functions

Dragan S. Janković, Ch. Konstadilaki-Savvopoulou (1992)

Mathematica Bohemica

Classes of functions continuous in various senses, in particular θ -continuous, α -continuous, feeblz continuous a.o., and relations between the classes, are studied.

On θ -closed sets and some forms of continuity

Mohammad Saleh (2004)

Archivum Mathematicum

In this paper, we further the study of θ -compactness a generalization of quasi-H-closed sets and its applications to some forms of continuity using θ -open and δ -open sets. Among other results, it is shown a weakly θ -retract of a Hausdorff space X is a δ -closed subset of X .

Openly factorizable spaces and compact extensions of topological semigroups

Taras O. Banakh, Svetlana Dimitrova (2010)

Commentationes Mathematicae Universitatis Carolinae

We prove that the semigroup operation of a topological semigroup S extends to a continuous semigroup operation on its Stone-Čech compactification β S provided S is a pseudocompact openly factorizable space, which means that each map f : S Y to a second countable space Y can be written as the composition f = g p of an open map p : X Z onto a second countable space Z and a map g : Z Y . We present a spectral characterization of openly factorizable spaces and establish some properties of such spaces.

Points of continuity and quasicontinuity

Ján Borsík (2010)

Open Mathematics

Let C(f), Q(f), E(f) and A(f) be the sets of all continuity, quasicontinuity, upper and lower quasicontinuity and cliquishness points of a real function f: X → ℝ, respectively. The triplets (C(f),Q(f),A(f)), (C(f),E(f),A(f) and (Q(f),E(f),A(f)are characterized for functions defined on Baire metric spaces without isolated points.

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