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Mappings on the dyadic solenoid

Jan M. Aarts, Robbert J. Fokkink (2003)

Commentationes Mathematicae Universitatis Carolinae

Answering an open problem in [3] we show that for an even number k , there exist no k to 1 mappings on the dyadic solenoid.

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.

Maps with dimensionally restricted fibers

Vesko Valov (2011)

Colloquium Mathematicae

We prove that if f: X → Y is a closed surjective map between metric spaces such that every fiber f - 1 ( y ) belongs to a class S of spaces, then there exists an F σ -set A ⊂ X such that A ∈ S and d i m f - 1 ( y ) A = 0 for all y ∈ Y. Here, S can be one of the following classes: (i) M: e-dim M ≤ K for some CW-complex K; (ii) C-spaces; (iii) weakly infinite-dimensional spaces. We also establish that if S = M: dim M ≤ n, then dim f ∆ g ≤ 0 for almost all g C ( X , n + 1 ) .

Marczewski-Burstin-like characterizations of σ-algebras, ideals, and measurable functions

Jack Brown, Hussain Elalaoui-Talibi (1999)

Colloquium Mathematicae

ℒ denotes the Lebesgue measurable subsets of ℝ and 0 denotes the sets of Lebesgue measure 0. In 1914 Burstin showed that a set M ⊆ ℝ belongs to ℒ if and only if every perfect P ∈ ℒ$ℒ0 h a s a p e r f e c t s u b s e t Q $ 0 which is a subset of or misses M (a similar statement omitting “is a subset of or” characterizes 0 ). In 1935, Marczewski used similar language to define the σ-algebra (s) which we now call the “Marczewski measurable sets” and the σ-ideal ( s 0 ) which we call the “Marczewski null sets”. M ∈ (s) if every perfect set P has...

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