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On the insertion of Darboux functions

Aleksander Maliszewski (1998)

Fundamenta Mathematicae

The main goal of this paper is to characterize the family of all functions f which satisfy the following condition: whenever g is a Darboux function and f < g on ℝ there is a Darboux function h such that f < h < g on ℝ.

On the pointwise limits of sequences of Świątkowski functions

Tomasz Natkaniec, Julia Wódka (2018)

Czechoslovak Mathematical Journal

The characterization of the pointwise limits of the sequences of Świątkowski functions is given. Modifications of Świątkowski property with respect to different topologies finer than the Euclidean topology are discussed.

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.

Path differentiation: further unification

Udayan Darji, Michael Evans (1995)

Fundamenta Mathematicae

A. M. Bruckner, R. J. O'Malley, and B. S. Thomson introduced path differentiation as a vehicle for unifying the theory of numerous types of generalized differentiation of real valued functions of a real variable. Part of their classification scheme was based on intersection properties of the underlying path systems. Here, additional light is shed on the relationships between these various types of path differentiation and it is shown how composite differentiation and first return differentiation...

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