Function spaces and shape theories

Jerzy Dydak ; Sławomir Nowak

Fundamenta Mathematicae, Tome 173 (2002), p. 117-154 / Harvested from The Polish Digital Mathematics Library

Résumé

The purpose of this paper is to provide a geometric explanation of strong shape theory and to give a fairly simple way of introducing the strong shape category formally. Generally speaking, it is useful to introduce a shape theory as a localization at some class of “equivalences”. We follow this principle and we extend the standard shape category Sh(HoTop) to Sh(pro-HoTop) by localizing pro-HoTop at shape equivalences. Similarly, we extend the strong shape category of Edwards-Hastings to sSh(pro-Top) by localizing pro-Top at strong shape equivalences. A map f:X → Y is a shape equivalence if and only if the induced function f*:[Y,P] → [X,P] is a bijection for all P ∈ ANR. A map f:X → Y of k-spaces is a strong shape equivalence if and only if the induced map f*: Map(Y,P) → Map(X,P) is a weak homotopy equivalence for all P ∈ ANR. One generalizes the concept of being a shape equivalence to morphisms of pro-HoTop without any problem and the only difficulty is to show that a localization of pro-HoTop at shape equivalences is a category (which amounts to showing that the morphisms form a set). Due to peculiarities of function spaces, extending the concept of strong shape equivalence to morphisms of pro-Top is more involved. However, it can be done and we show that the corresponding localization exists. One can introduce the concept of a super shape equivalence f:X → Y of topological spaces as a map such that the induced map f*: Map(Y,P) → Map(X,P) is a homotopy equivalence for all P ∈ ANR, and one can extend it to morphisms of pro-Top. However, the authors do not know if the corresponding localization exists. Here are applications of our methods: Theorem. A map f:X → Y of k-spaces is a strong shape equivalence if and only if $f × id_Q: X ×_k Q → Y ×_k Q$ is a shape equivalence for each CW complex Q. Theorem. Suppose f: X → Y is a map of topological spaces. (a) f is a shape equivalence if and only if the induced function f*: [Y,M] → [X,M] is a bijection for all M = Map(Q,P), where P ∈ ANR and Q is a finite CW complex. (b) If f is a strong shape equivalence, then the induced function f*: [Y,M] → [X,M] is a bijection for all M = Map(Q,P), where P ∈ ANR and Q is an arbitrary CW complex. (c) If X, Y are k-spaces and the induced function f*: [Y,M] → [X,M] is a bijection for all M = Map(Q,P), where P ∈ ANR and Q is an arbitrary CW complex, then f is a strong shape equivalence.

Détail

Publié le : 2002-01-01

Zbl 0989.55008

EUDML-ID : urn:eudml:doc:282758