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Functional characterizations of p-spaces

Ľubica Holá (2013)

Open Mathematics

We show that a completely regular space Y is a p-space (a Čech-complete space, a locally compact space) if and only if given a dense subspace A of any topological space X and a continuous f: A → Y there are a p-embedded subset (resp. a G δ-subset, an open subset) M of X containing A and a quasicontinuous subcontinuous extension f*: M → Y of f continuous at every point of A. A result concerning a continuous extension to a residual set is also given.

Functor of extension of Λ -isometric maps between central subsets of the unbounded Urysohn universal space

Piotr Niemiec (2010)

Commentationes Mathematicae Universitatis Carolinae

The aim of the paper is to prove that in the unbounded Urysohn universal space 𝕌 there is a functor of extension of Λ -isometric maps (i.e. dilations) between central subsets of 𝕌 to Λ -isometric maps acting on the whole space. Special properties of the functor are established. It is also shown that the multiplicative group { 0 } acts continuously on 𝕌 by Λ -isometries.

Further characterizations of boundedly UC spaces

Ľubica Holá, Dušan Holý (1993)

Commentationes Mathematicae Universitatis Carolinae

Following the paper [BDC1], further relations between the classical topologies on function spaces and new ones induced by hyperspace topologies on graphs of functions are introduced and further characterizations of boundedly UC spaces are given.

Further properties of 1-sequence-covering maps

Tran Van An, Luong Quoc Tuyen (2008)

Commentationes Mathematicae Universitatis Carolinae

Some relationships between 1 -sequence-covering maps and weak-open maps or sequence-covering s -maps are discussed. These results are used to generalize a result from Lin S., Yan P., Sequence-covering maps of metric spaces, Topology Appl. 109 (2001), 301–314.

Fuzzy distances

Josef Bednář (2005)

Kybernetika

In the paper, three different ways of constructing distances between vaguely described objects are shown: a generalization of the classic distance between subsets of a metric space, distance between membership functions of fuzzy sets and a fuzzy metric introduced by generalizing a metric space to fuzzy-metric one. Fuzzy metric spaces defined by Zadeh’s extension principle, particularly to n are dealt with in detail.

g -metrizable spaces and the images of semi-metric spaces

Ying Ge, Shou Lin (2007)

Czechoslovak Mathematical Journal

In this paper, we prove that a space X is a g -metrizable space if and only if X is a weak-open, π and σ -image of a semi-metric space, if and only if X is a strong sequence-covering, quotient, π and m s s c -image of a semi-metric space, where “semi-metric” can not be replaced by “metric”.

Currently displaying 561 – 580 of 1678