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Displaying 101 – 120 of 522

Closed mappings which lower dimension

James Keesling (1969)

Colloquium Mathematicae

Compact images of spaces with a weaker metric topology

Peng-fei Yan, Cheng Lü (2008)

Czechoslovak Mathematical Journal

If $X$ is a space that can be mapped onto a metric space by a one-to-one mapping, then $X$ is said to have a weaker metric topology. In this paper, we give characterizations of sequence-covering compact images and sequentially-quotient compact images of spaces with a weaker metric topology. The main results are that (1) $Y$ is a sequence-covering compact image of a space with a weaker metric topology if and only if $Y$ has a sequence ${ℱ_{i}}_{i \in ℕ}$ of point-finite $c s$ -covers such that $⋂_{i \in ℕ} st (y, ℱ_{i}) = {y}$ for each $y \in Y$ . (2) $Y$ is a sequentially-quotient...

Complements of solenoids in $S^{3}$ are m-spaces

G. Michaelides (1977)

Fundamenta Mathematicae

Completely continuous images of nearly paracomact spaces

T. Noiri (1977)

Matematički Vesnik

Completely $N$ -continuous multifunctions.

Ekici, Erdal (2005)

Divulgaciones Matemáticas

Component restriction property for classes of mappings.

Charatonik, Janusz J. (2003)

Mathematica Pannonica

Compositions of confluent mappings and some other classes of functions

A. Lelek, David R. Read (1974)

Colloquium Mathematicae

Compositions of simple maps

Jerzy Krzempek (1999)

Fundamenta Mathematicae

A map (= continuous function) is of order ≤ k if each of its point-inverses has at most k elements. Following [4], maps of order ≤ 2 are called simple. Which maps are compositions of simple closed [open, clopen] maps? How many simple maps are really needed to represent a given map? It is proved herein that every closed map of order ≤ k defined on an n-dimensional metric space is a composition of (n+1)k-1 simple closed maps (with metric domains). This theorem fails to be true...

Concerning Splittability and Perfect Mappings

A. V. Arhangel'skii, Ljubiša Kočinac (1990)

Publications de l'Institut Mathématique

Condensations of Cartesian products

Oleg I. Pavlov (1999)

Commentationes Mathematicae Universitatis Carolinae

We consider when one-to-one continuous mappings can improve normality-type and compactness-type properties of topological spaces. In particular, for any Tychonoff non-pseudocompact space $X$ there is a $μ$ such that $X^{μ}$ can be condensed onto a normal ( $σ$ -compact) space if and only if there is no measurable cardinal. For any Tychonoff space $X$ and any cardinal $ν$ there is a Tychonoff space $M$ which preserves many properties of $X$ and such that any one-to-one continuous image of $M^{μ}$ , $μ \leq ν$ , contains a closed copy...