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Hereditarily weakly confluent induced mappings are homeomorphisms

Janusz CharatonikWłodzimierz Charatonik — 1998

Colloquium Mathematicae

For a given mapping f between continua we consider the induced mappings between the corresponding hyperspaces of closed subsets or of subcontinua. It is shown that if either of the two induced mappings is hereditarily weakly confluent (or hereditarily confluent, or hereditarily monotone, or atomic), then f is a homeomorphism, and consequently so are both the induced mappings. Similar results are obtained for mappings between cones over the domain and over the range continua.

Induced near-homeomorphisms

Włodzimierz J. Charatonik — 2000

Commentationes Mathematicae Universitatis Carolinae

We construct examples of mappings f and g between locally connected continua such that 2 f and C ( f ) are near-homeomorphisms while f is not, and 2 g is a near-homeomorphism, while g and C ( g ) are not. Similar examples for refinable mappings are constructed.

On Mazurkiewicz sets

Marta N. CharatonikWłodzimierz J. Charatonik — 2000

Commentationes Mathematicae Universitatis Carolinae

A Mazurkiewicz set M is a subset of a plane with the property that each straight line intersects M in exactly two points. We modify the original construction to obtain a Mazurkiewicz set which does not contain vertices of an equilateral triangle or a square. This answers some questions by L.D. Loveland and S.M. Loveland. We also use similar methods to construct a bounded noncompact, nonconnected generalized Mazurkiewicz set.

Arc property of Kelley and absolute retracts for hereditarily unicoherent continua

Janusz J. CharatonikWłodzimierz J. CharatonikJanusz R. Prajs — 2003

Colloquium Mathematicae

We investigate absolute retracts for hereditarily unicoherent continua, and also the continua that have the arc property of Kelley (i.e., the continua that satisfy both the property of Kelley and the arc approximation property). Among other results we prove that each absolute retract for hereditarily unicoherent continua (for tree-like continua, for λ-dendroids, for dendroids) has the arc property of Kelley.

Hyperspace retractions for curves

AbstractWe study retractions from the hyperspace of all nonempty closed subsets of a given continuum onto the continuum (which is naturally embedded in the hyperspace). Some necessary and some sufficient conditions for the existence of such a retraction are found if the continuum is a curve. It is shown that the existence of such a retraction for a curve implies that the curve is a uniformly arcwise connected dendroid, and that a universal smooth dendroid admits such a retraction. The existence...

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