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Metrizability of σ -frames

M. Mehdi Ebrahimi, M. Vojdani Tabatabaee, M. Mahmoudi (2004)

Cahiers de Topologie et Géométrie Différentielle Catégoriques

Metrization criteria for compact groups in terms of their dense subgroups

Dikran Dikranjan, Dmitri Shakhmatov (2013)

Fundamenta Mathematicae

According to Comfort, Raczkowski and Trigos-Arrieta, a dense subgroup D of a compact abelian group G determines G if the restriction homomorphism Ĝ → D̂ of the dual groups is a topological isomorphism. We introduce four conditions on D that are necessary for it to determine G and we resolve the following question: If one of these conditions holds for every dense (or G δ -dense) subgroup D of G, must G be metrizable? In particular, we prove (in ZFC) that a compact abelian group determined by all its...

Metrization of function spaces with the Fell topology

Hanbiao Yang (2012)

Commentationes Mathematicae Universitatis Carolinae

For a Tychonoff space X , let C F ( X ) be the family of hypographs of all continuous maps from X to [ 0 , 1 ] endowed with the Fell topology. It is proved that X has a dense separable metrizable locally compact open subset if C F ( X ) is metrizable. Moreover, for a first-countable space X , C F ( X ) is metrizable if and only if X itself is a locally compact separable metrizable space. There exists a Tychonoff space X such that C F ( X ) is metrizable but X is not first-countable.

Mildly ( 1 , 2 ) * -normal spaces and some bitopological functions

K. Kayathri, O. Ravi, M. L. Thivagar, M. Joseph Israel (2010)

Mathematica Bohemica

The aim of the paper is to introduce and study a new class of spaces called mildly ( 1 , 2 ) * -normal spaces and a new class of functions called ( 1 , 2 ) * - rg -continuous, ( 1 , 2 ) * - R -map, almost ( 1 , 2 ) * -continuous function and almost ( 1 , 2 ) * - rg -closed function in bitopological spaces. Subsequently, the relationships between mildly ( 1 , 2 ) * -normal spaces and the new bitopological functions are investigated. Moreover, we obtain characterizations of mildly ( 1 , 2 ) * -normal spaces, properties of the new bitopological functions and preservation theorems for...

Minimal bi-Lipschitz embedding dimension of ultrametric spaces

Jouni Luukkainen, Hossein Movahedi-Lankarani (1994)

Fundamenta Mathematicae

We prove that an ultrametric space can be bi-Lipschitz embedded in n if its metric dimension in Assouad’s sense is smaller than n. We also characterize ultrametric spaces up to bi-Lipschitz homeomorphism as dense subspaces of ultrametric inverse limits of certain inverse sequences of discrete spaces.

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