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Mapping theorems on -spaces

Masami Sakai (2008)

Commentationes Mathematicae Universitatis Carolinae

In this paper we improve some mapping theorems on -spaces. For instance we show that an -space is preserved by a closed and countably bi-quotient map. This is an improvement of Yun Ziqiu’s theorem: an -space is preserved by a closed and open map.

Mappings related to confluence

Janusz Jerzy Charatonik (1996)

Archivum Mathematicum

Necessary and sufficient conditions are found in the paper for a mapping between continua to be monotone, confluent, semi-confluent, joining, weakly confluent and pseudo-confluent. Three lists of these conditions are presented. Two are formulated in terms of components and of quasi-components, respectively, of connected closed subsets of the range space, while the third one in terms of connectedness between subsets of the domain space. Some basic relations concerning these concepts are studied.

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.

Monotone homogeneity of dendrites

Janusz Jerzy Charatonik, Włodzimierz J. Charatonik (1997)

Commentationes Mathematicae Universitatis Carolinae

Sufficient as well as necessary conditions are studied for a dendrite or a dendroid to be homogeneous with respect to monotone mappings. The obtained results extend ones due to H. Kato and the first named author. A number of open problems are asked.

Monotone retractions and depth of continua

Janusz Jerzy Charatonik, Panayotis Spyrou (1994)

Archivum Mathematicum

It is shown that for every two countable ordinals α and β with α > β there exist λ -dendroids X and Y whose depths are α and β respectively, and a monotone retraction from X onto Y . Moreover, the continua X and Y can be either both arclike or both fans.

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