Extending Stechkin's theorem and beyond.
Extending the ideal of nowhere dense subsets of rationals to a P-ideal
We show that the ideal of nowhere dense subsets of rationals cannot be extended to an analytic P-ideal, ideal nor maximal P-ideal. We also consider a problem of extendability to a non-meager P-ideals (in particular, to maximal P-ideals).
Extension and reconstruction theorems for the Urysohn universal metric space
We prove some extension theorems involving uniformly continuous maps of the universal Urysohn space. As an application, we prove reconstruction theorems for certain groups of autohomeomorphisms of this space and of its open subsets.
Extension and Selection theorems in Topological spaces with a generalized convexity structure
Extension du principe de prolongement des identites aux applications des espaces semi-topogenes
Extension of bilipschitz maps of compact polyhedra.
Extension of closed mappings
Extension of functions with small oscillation
A classical theorem of Kuratowski says that every Baire one function on a subspace of a Polish (= separable completely metrizable) space X can be extended to a Baire one function on X. Kechris and Louveau introduced a finer gradation of Baire one functions into small Baire classes. A Baire one function f is assigned into a class in this hierarchy depending on its oscillation index β(f). We prove a refinement of Kuratowski’s theorem: if Y is a subspace of a metric space X and f is a real-valued...
Extension of Lipschitz functions defined on metric subspaces of homogeneous type.
If a metric subspace Mº of an arbitrary metric space M carries a doubling measure μ, then there is a simultaneous linear extension of all Lipschitz functions on Mº ranged in a Banach space to those on M. Moreover, the norm of this linear operator is controlled by logarithm of the doubling constant of μ.
Extension of Lipschitz mappings on metric trees
Extension of locally uniformly equivalent metrics
Extension of measures: a categorical approach
We present a categorical approach to the extension of probabilities, i.e. normed -additive measures. J. Novák showed that each bounded -additive measure on a ring of sets is sequentially continuous and pointed out the topological aspects of the extension of such measures on over the generated -ring : it is of a similar nature as the extension of bounded continuous functions on a completely regular topological space over its Čech-Stone compactification (or as the extension of continuous...
Extension of measures and integrals by the help of a pseudometric
Extension of multisequences and countably uniradial classes of topologies
It is proved that every non trivial continuous map between the sets of extremal elements of monotone sequential cascades can be continuously extended to some subcascades. This implies a result of Franklin and Rajagopalan that an Arens space cannot be continuously non trivially mapped to an Arens space of higher rank. As an application, it is proved that if for a filter on , the class of -radial topologies contains each sequential topology, then it includes the class of subsequential topologies....
Extension of point-finite partitions of unity
A subspace A of a topological space X is said to be -embedded ((point-finite)-embedded) in X if every (point-finite) partition of unity α on A with |α| ≤ γ extends to a (point-finite) partition of unity on X. The main results are: (Theorem A) A subspace A of X is (point-finite)-embedded in X iff it is -embedded and every countable intersection B of cozero-sets in X with B ∩ A = ∅ can be separated from A by a cozero-set in X. (Theorem B) The product A × [0,1] is (point-finite)-embedded in X...
Extension of sequentially continuous mappings
Extension of the Kirk-Saliga fixed point theorem.
Extension operators on balls and on spaces of finite sets
We study extension operators between spaces of continuous functions on the spaces of subsets of X of cardinality at most n. As an application, we show that if is the unit ball of a nonseparable Hilbert space H equipped with the weak topology, then, for any 0 < λ < μ, there is no extension operator .
Extension properties of Stone-Čech coronas and proper absolute extensors
We characterize, in terms of X, the extensional dimension of the Stone-Čech corona βX∖X of a locally compact and Lindelöf space X. The non-Lindelöf case is also settled in terms of extending proper maps with values in , where L is a finite complex. Further, for a finite complex L, an uncountable cardinal τ and a -set X in the Tikhonov cube we find a necessary and sufficient condition, in terms of , for X to be in the class AE([L]). We also introduce a concept of a proper absolute extensor and...
Extension theorem for a pseudo-arc