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On absolutely submetrizable spaces

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.

On AP and WAP spaces

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) C p over σ -compact space is AP. Therefore AP does not imply even pseudoradiality in function spaces, while...

On Applications of Bing-Krasinkiewicz-Lelek Maps

Eiichi Matsuhashi (2007)

Bulletin of the Polish Academy of Sciences. Mathematics

We characterize Peano continua using Bing-Krasinkiewicz-Lelek maps. Also we deal with some topics on Whitney preserving maps.

On character and chain conditions in images of products

Murray Bell (1998)

Fundamenta Mathematicae

A scadic space is a Hausdorff continuous image of a product of compact scattered spaces. We complete a theorem begun by G. Chertanov that will establish that for each scadic space X, χ(X) = w(X). A ξ-adic space is a Hausdorff continuous image of a product of compact ordinal spaces. We introduce an either-or chain condition called Property R λ ' which we show is satisfied by all ξ-adic spaces. Whereas Property R λ ' is productive, we show that a weaker (but more natural) Property R λ is not productive. Polyadic...

On character of points in the Higson corona of a metric space

Taras O. Banakh, Ostap Chervak, Lubomyr Zdomskyy (2013)

Commentationes Mathematicae Universitatis Carolinae

We prove that for an unbounded metric space X , the minimal character 𝗆 χ ( X ˇ ) of a point of the Higson corona X ˇ of X is equal to 𝔲 if X has asymptotically isolated balls and to max { 𝔲 , 𝔡 } otherwise. This implies that under 𝔲 < 𝔡 a metric space X of bounded geometry is coarsely equivalent to the Cantor macro-cube 2 < if and only if dim ( X ˇ ) = 0 and 𝗆 χ ( X ˇ ) = 𝔡 . This contrasts with a result of Protasov saying that under CH the coronas of any two asymptotically zero-dimensional unbounded metric separable spaces are homeomorphic.

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