Sequentially continuous mappings of product spaces
Set-valued mappings on metric spaces
Several extremal coreflective classes in uniform spaces
Shape properties of hyperspaces
Shape theory of maps.
We shall describe a modification of homotopy theory of maps which we call shape theory of maps. This is accomplished by constructing the shape category of maps HMb. The category HMb is built using multi-valued functions. Its objects are maps of topological spaces while its morphisms are homotopy classes of collections of pairs of multi-valued functions which we call multi-binets. Various authors have previously given other descriptions of shape categories of maps. Our description is intrinsic in...
Sheaves and local equivalence relations
Sheaves of metric lattices
Size levels for arcs
We determine the size levels for any function on the hyperspace of an arc as follows. Assume Z is a continuum and consider the following three conditions: 1) Z is a planar AR; 2) cut points of Z have component number two; 3) any true cyclic element of Z contains at most two cut points of Z. Then any size level for an arc satisfies 1)-3) and conversely, if Z satisfies 1)-3), then Z is a diameter level for some arc.
Skeletal maps and I-favorable spaces
Skeletally Dugundji spaces
We introduce and investigate the class of skeletally Dugundji spaces as a skeletal analogue of Dugundji space. Our main result states that the following conditions are equivalent for a given space X: (i) X is skeletally Dugundji; (ii) every compactification of X is co-absolute to a Dugundji space; (iii) every C*-embedding of the absolute p(X) in another space is strongly π-regular; (iv) X has a multiplicative lattice in the sense of Shchepin [Shchepin E.V., Topology of limit spaces with uncountable...
Small-fibred semitopological functors without small-fibred initial completions
Smooth dendroids as inverse limits of dendrites
Sobre el teorema de inmersión de Mrówka.
Certain equivalences of Mrowka's separating condition enable us to characterize when parametric maps are open, closed or quotient.
Sobriety and localic compactness in categories of -bitopological spaces.
Some complexity results in topology and analysis
If X is a compact metric space of dimension n, then K(X), the n- dimensional kernel of X, is the union of all n-dimensional Cantor manifolds in X. Aleksandrov raised the problem of what the descriptive complexity of K(X) could be. A straightforward analysis shows that if X is an n-dimensional complete separable metric space, then K(X) is a or PCA set. We show (a) there is an n-dimensional continuum X in for which K(X) is a complete set. In particular, ; K(X) is coanalytic but is not an analytic...
Some continuous separation axioms
Some covering spaces and types of compactness.
Some examples of true sets
Let K(X) be the hyperspace of a compact metric space endowed with the Hausdorff metric. We give a general theorem showing that certain subsets of K(X) are true sets.
Some factorization theorems for closed subspaces
Some further aspects of G. Preuss' theory of E-connected spaces