-neighborhood groups.
-stability of Picard iteration in metric spaces.
Tests à la Hurewicz dans le plan
Nous donnons, pour une certaine catégorie de boréliens d'un produit de deux espaces polonais, comprenant les boréliens à coupes dénombrables, une caractérisation du type "test d'Hurewicz" de ceux ne pouvant pas être rendus différence transfinie d'ouverts par changement des deux topologies polonaises.
The Abel equation and total solvability of linear functional equations
We investigate the solvability in continuous functions of the Abel equation φ(Fx) - φ(x) = 1 where F is a given continuous mapping of a topological space X. This property depends on the dynamics generated by F. The solvability of all linear equations P(x)ψ(Fx) + Q(x)ψ(x) = γ(x) follows from solvability of the Abel equation in case F is a homeomorphism. If F is noninvertible but X is locally compact then such a total solvability is determined by the same property of the cohomological equation φ(Fx)...
The a-congruences on S(X) and the S-equivalences on X.
The Alexandroff-Urysohn square and the fixed point property.
The automorphism group of the Lebesgue measure has no non-trivial subgroups of index
We show that the automorphism group Aut([0,1],λ) of the Lebesgue measure has no non-trivial subgroups of index .
The Baire property in remainders of topological groups and other results
It is established that a remainder of a non-locally compact topological group has the Baire property if and only if the space is not Čech-complete. We also show that if is a non-locally compact topological group of countable tightness, then either is submetrizable, or is the Čech-Stone remainder of an arbitrary remainder of . It follows that if and are non-submetrizable topological groups of countable tightness such that some remainders of and are homeomorphic, then the spaces...
The Banach contraction mapping principle and cohomology.
The Banach contraction mapping principle and cohomology
By a dynamical system we mean the action of the semigroup on a metrizable topological space induced by a continuous selfmap . Let denote the set of all compatible metrics on the space . Our main objective is to show that a selfmap of a compact space is a Banach contraction relative to some if and only if there exists some which, regarded as a -cocycle of the system , is a coboundary.
The behaviour of the nonwandering set of a piecewise monotonic interval map under small perturbations
In this paper piecewise monotonic maps are considered. Let be a finite union of open intervals, and consider the set of all points whose orbits omit . The influence of small perturbations of the endpoints of the intervals in on the dynamical system is investigated. The decomposition of the nonwandering set into maximal topologically transitive subsets behaves very unstably. Nonetheless, it is shown that a maximal topologically transitive subset cannot be completely destroyed by arbitrary...
The best approximation and an extension of a fixed point theorem of F. E. Browder.
The Bohr compactification, modulo a metrizable subgroup
The authors prove the following result, which generalizes a well-known theorem of I. Glicksberg [G]: If G is a locally compact Abelian group with Bohr compactification bG, and if N is a closed metrizable subgroup of bG, then every A ⊆ G satisfies: A·(N ∩ G) is compact in G if and only if {aN:a ∈ A} is compact in bG/N. Examples are given to show: (a) the asserted equivalence can fail in the absence of the metrizability hypothesis, even when N ∩ G = {1}; (b) the asserted equivalence can hold for suitable...
The Borel structure of the collections of sub-self-similar sets and super-self-similar sets.
The boundary-Wecken classification of surfaces.
The Box Dimension of Completely Invariant Subsets for Expanding Piecewise Monotonic Transformations.
The branch locus for one-dimensional Pisot tiling spaces
If φ is a Pisot substitution of degree d, then the inflation and substitution homeomorphism Φ on the tiling space factors via geometric realization onto a d-dimensional solenoid. Under this realization, the collection of Φ-periodic asymptotic tilings corresponds to a finite set that projects onto the branch locus in a d-torus. We prove that if two such tiling spaces are homeomorphic, then the resulting branch loci are the same up to the action of certain affine maps on the torus.
The centralizer of Morse shifts induced by arbitrary blocks
The characterization of the cut of funnel in a planar semidynamical system
The coarsest topology for -approximately continuous functions