Displaying similar documents to “Spaces with countable s n -networks”

On remote points, non-normality and π -weight ω 1

Sergei Logunov (2001)

Commentationes Mathematicae Universitatis Carolinae

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We show, in particular, that every remote point of X is a nonnormality point of β X if X is a locally compact Lindelöf separable space without isolated points and π w ( X ) ω 1 .

Some non-multiplicative properties are l -invariant

Vladimir Vladimirovich Tkachuk (1997)

Commentationes Mathematicae Universitatis Carolinae

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A cardinal function ϕ (or a property 𝒫 ) is called l -invariant if for any Tychonoff spaces X and Y with C p ( X ) and C p ( Y ) linearly homeomorphic we have ϕ ( X ) = ϕ ( Y ) (or the space X has 𝒫 ( X 𝒫 ) iff Y 𝒫 ). We prove that the hereditary Lindelöf number is l -invariant as well as that there are models of Z F C in which hereditary separability is l -invariant.

Ramsey-like properties for bi-Lipschitz mappings of finite metric spaces

Jiří Matoušek (1992)

Commentationes Mathematicae Universitatis Carolinae

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Let ( X , ρ ) , ( Y , σ ) be metric spaces and f : X Y an injective mapping. We put f L i p = sup { σ ( f ( x ) , f ( y ) ) / ρ ( x , y ) ; x , y X , x y } , and dist ( f ) = f L i p . f - 1 L i p (the of the mapping f ). Some Ramsey-type questions for mappings of finite metric spaces with bounded distortion are studied; e.g., the following theorem is proved: Let X be a finite metric space, and let ε > 0 , K be given numbers. Then there exists a finite metric space Y , such that for every mapping f : Y Z ( Z arbitrary metric space) with dist ( f ) < K one can find a mapping g : X Y , such that both the mappings g and f | g ( X ) have distortion...