On a metrization of the hyperspace of a metric space
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Karol Borsuk (1977)
Fundamenta Mathematicae
Raushan Z. Buzyakova (2006)
Commentationes Mathematicae Universitatis Carolinae
We introduce a notion of absolute submetrizability (= ``every Tychonoff subtopology is submetrizable'') and investigate its behavior under basic topological operations. The main result is an example of an absolutely submetrizable space that contains an uncountable set of isolated points (hence the space is neither separable nor hereditarily Lindelöf). This example is used to show that absolute submetrizability is not preserved by some topological operations, in particular, by free sums.
Angelo Bella, Ivan V. Yashchenko (1999)
Commentationes Mathematicae Universitatis Carolinae
Several remarks on the properties of approximation by points (AP) and weak approximation by points (WAP) are presented. We look in particular at their behavior in product and at their relationships with radiality, pseudoradiality and related concepts. For instance, relevant facts are: (a) There is in ZFC a product of a countable WAP space with a convergent sequence which fails to be WAP. (b) over -compact space is AP. Therefore AP does not imply even pseudoradiality in function spaces, while...
Szymon Plewik (1988)
Czechoslovak Mathematical Journal
Raushan Z. Buzyakova (2002)
Commentationes Mathematicae Universitatis Carolinae
It is shown that every strong space is a -space. In particular, it follows that every paracompact space is a -space.
Y. Kodama, J. Ono (1980)
Fundamenta Mathematicae
Juliusz Olędzki (1975)
Fundamenta Mathematicae
J. Hunt (1972)
Fundamenta Mathematicae
Kiiti Morita (1975)
Fundamenta Mathematicae
Thomas Sanders (1974)
Fundamenta Mathematicae
K. Alster (1987)
Fundamenta Mathematicae
I. Juhász, W. Weiss (1978)
Colloquium Mathematicae
Liang-Xue Peng (2010)
Commentationes Mathematicae Universitatis Carolinae
In this note, we introduce the concept of weakly monotonically monolithic spaces, and show that every weakly monotonically monolithic space is a -space. Thus most known conclusions on -spaces can be obtained by this conclusion. As a corollary, we have that if a regular space is sequential and has a point-countable -network then is a -space.
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