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On generalized topological spaces I

Artur Piękosz (2013)

Annales Polonici Mathematici

We begin a systematic study of the category GTS of generalized topological spaces (in the sense of H. Delfs and M. Knebusch) and their strictly continuous mappings. We reformulate the axioms. Generalized topology is found to be connected with the concept of a bornological universe. Both GTS and its full subcategory SS of small spaces are topological categories. The second part of this paper will also appear in this journal.

On generalized topological spaces II

Artur Piękosz (2013)

Annales Polonici Mathematici

This is the second part of A. Piękosz [Ann. Polon. Math. 107 (2013), 217-241]. The categories GTS(M), with M a non-empty set, are shown to be topological. Several related categories are proved to be finitely complete. Locally small and nice weakly small spaces can be described using certain sublattices of power sets. Some important elements of the theory of locally definable and weakly definable spaces are reconstructed in a wide context of structures with topologies.

On hereditary and product-stable quotient maps

Friedhelm Schwarz, Sibylle Weck-Schwarz (1992)

Commentationes Mathematicae Universitatis Carolinae

It is shown that the quotient maps of a monotopological construct A which are preserved by pullbacks along embeddings, projections, or arbitrary morphisms, can be characterized by being quotient maps in appropriate extensions of A.

On hit-and-miss hyperspace topologies

Gerald Beer, Robert K. Tamaki (1993)

Commentationes Mathematicae Universitatis Carolinae

The Vietoris topology and Fell topologies on the closed subsets of a Hausdorff uniform space are prototypes for hit-and-miss hyperspace topologies, having as a subbase all closed sets that hit a variable open set, plus all closed sets that miss (= fail to intersect) a variable closed set belonging to a prescribed family Δ of closed sets. In the case of the Fell topology, where Δ consists of the compact sets, a closed set A misses a member B of Δ if and only if A is far from B in a uniform sense....

On indecomposability and composants of chaotic continua

Hisao Kato (1996)

Fundamenta Mathematicae

A homeomorphism f:X → X of a compactum X with metric d is expansive if there is c > 0 such that if x,y ∈ X and x ≠ y, then there is an integer n ∈ ℤ such that d ( f n ( x ) , f n ( y ) ) > c . A homeomorphism f: X → X is continuum-wise expansive if there is c > 0 such that if A is a nondegenerate subcontinuum of X, then there is an integer n ∈ ℤ such that d i a m i f n ( A ) > c . Clearly, every expansive homeomorphism is continuum-wise expansive, but the converse assertion is not true. In [6], we defined the notion of chaotic continua of homeomorphisms...

On linear functorial operators extending pseudometrics

Taras O. Banakh, Oleg Pikhurko (1997)

Commentationes Mathematicae Universitatis Carolinae

For a functor F I d on the category of metrizable compacta, we introduce a conception of a linear functorial operator T = { T X : P c ( X ) P c ( F X ) } extending (for each X ) pseudometrics from X onto F X X (briefly LFOEP for F ). The main result states that the functor S P G n of G -symmetric power admits a LFOEP if and only if the action of G on { 1 , , n } has a one-point orbit. Since both the hyperspace functor exp and the probability measure functor P contain S P 2 as a subfunctor, this implies that both exp and P do not admit LFOEP.

Currently displaying 61 – 80 of 187