We prove that, for every countable ordinal α ≥ 3, there exists countable completely regular spaces Xα and Yα such that the spaces Cp (Xα ) and Cp (Yα ) are borelian of class exactly Mα , but are not homeomorphic.
2000 Mathematics Subject Classification: 54C55, 54H25, 55M20. We introduce the class of algebraic ANRs. It is defined by replacing continuous maps by chain mappings in Lefschetz’s characterization of ANRs. To a large extent, the theory of algebraic ANRs parallels the classical theory of ANRs. Every ANR is an algebraic ANR, but the class of algebraic ANRs is much larger; the most striking difference between these classes is that every locally equiconnected metrisable space is an algebraic ANR,...
2000 Mathematics Subject Classification: 54H25, 55M20. The aim of this paper is to define a fixed point index for compact maps in the class of algebraic ANRs. This class, which we introduced in [2], contains all open subsets of convex subsets of metrizable topological vector spaces. In this class, it is convenient to study the fixed points of compact maps with the help of the chain morphisms that they induce on the singular chains. For this reason, we first define a fixed point index...
We prove that a metric space is an ANR if, and only if, every open subset of X has the homotopy type of a CW-complex.
For A ⊂ I = [0,1], let be the set of continuous real-valued functions on I which vanish on a neighborhood of A. We prove that if A is an analytic subset which is not an and whose closure has an empty interior, then is homeomorphic to the space of differentiable functions from I into ℝ.
We prove that a k-dimensional hereditarily indecomposable metrisable continuum is not a -valued absolute retract. We deduce from this that none of the classical characterizations of ANR (metric) extends to the class of stratifiable spaces.
We construct the example of the title.
We prove the existence, in the Hilbert space, of an absorbing set for the nth projective class.
We give an example in the Hilbert space of two subsets which are absorbing for the class of topologically complete spaces, but for which there exists no homeomorphism of onto itself mapping one of these subsets onto the other.
Let D (resp. D*) be the subspace of C = C([0,1], R) consisting of differentiable functions (resp. of functions differentiable at the one point at least). We give topological characterizations of the pairs (C, D) and (C, D*) and use them to give some examples of spaces homeomorphic to CDor to CD*.
Let X and Y be metric compacta such that there exists a continuous open surjection from onto . We prove that if there exists an integer k such that is strongly infinite-dimensional, then there exists an integer p such that is strongly infinite-dimensional.
Page 1 Next