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Decomposable hulls of multifunctions

Andrzej Nowak, Celina Rom (2002)

Discussiones Mathematicae, Differential Inclusions, Control and Optimization

Let F be a multifunction with values in Lₚ(Ω, X). In this note, we study which regularity properties of F are preserved when we consider the decomposable hull of F.

Decomposing Borel functions using the Shore-Slaman join theorem

Takayuki Kihara (2015)

Fundamenta Mathematicae

Jayne and Rogers proved that every function from an analytic space into a separable metrizable space is decomposable into countably many continuous functions with closed domains if and only if the preimage of each F σ set under that function is again F σ . Many researchers conjectured that the Jayne-Rogers theorem can be generalized to all finite levels of Borel functions. In this paper, by using the Shore-Slaman join theorem on the Turing degrees, we show the following variant of the Jayne-Rogers theorem...

Decompositions of cyclic elements of locally connected continua

D. Daniel (2010)

Colloquium Mathematicae

Let X denote a locally connected continuum such that cyclic elements have metrizable G δ boundary in X. We study the cyclic elements of X by demonstrating that each such continuum gives rise to an upper semicontinuous decomposition G of X into continua such that X/G is the continuous image of an arc and the cyclic elements of X correspond to the cyclic elements of X/G that are Peano continua.

Decreasing (G) spaces

Ian Stares (1998)

Commentationes Mathematicae Universitatis Carolinae

We consider the class of decreasing (G) spaces introduced by Collins and Roscoe and address the question as to whether it coincides with the class of decreasing (A) spaces. We provide a partial solution to this problem (the answer is yes for homogeneous spaces). We also express decreasing (G) as a monotone normality type condition and explore the preservation of decreasing (G) type properties under closed maps. The corresponding results for decreasing (A) spaces are unknown.

Dedekind cuts in C(X)

Nicolae Dăneţ (2011)

Banach Center Publications

The aim of this paper is to show that every Hausdorff continuous interval-valued function on a completely regular topological space X corresponds to a Dedekind cut in C(X) and conversely.

Definable completeness

Marta Bunge, Mamumka Jibladze, Thomas Streicher (2004)

Cahiers de Topologie et Géométrie Différentielle Catégoriques

Definably complete Baire structures

Antongiulio Fornasiero, Tamara Servi (2010)

Fundamenta Mathematicae

We consider definably complete Baire expansions of ordered fields: every definable subset of the domain of the structure has a supremum and the domain cannot be written as the union of a definable increasing family of nowhere dense sets. Every expansion of the real field is definably complete and Baire, and so is every o-minimal expansion of a field. Moreover, unlike the o-minimal case, the structures considered form an axiomatizable class. In this context we prove a version of the Kuratowski-Ulam...

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