ArticleOriginal scientific text

Title

Fundamental pro-groupoids and covering projections

Authors 1

Affiliations

  1. Departamento de Matemáticas, Universidad de Zaragoza, 50009 Zaragoza, Spain

Abstract

We introduce a new notion of covering projection E → X of a topological space X which reduces to the usual notion if X is locally connected. We use locally constant presheaves and covering reduced sieves to find a pro-groupoid π crs (X) and an induced category pro (π crs (X), Sets) such that for any topological space X the category of covering projections and transformations of X is equivalent to the category pro (π crs (X), Sets). We also prove that the latter category is equivalent to pro (π CX, Sets), where π CX is the Čech fundamental pro-groupoid of X. If X is locally path-connected and semilocally 1-connected, we show that π crs (X) is weakly equivalent to π X, the standard fundamental groupoid of X, and in this case pro (π crs (X), Sets) is equivalent to the functor category SetsπX. If (X,*) is a pointed connected compact metrisable space and if (X,*) is 1-movable, then the category of covering projections of X is equivalent to the category of continuous checkπ1(X,)-sets, where checkπ1(X,) is the Čech fundamental group provided with the inverse limit topology.

Keywords

covering projection, covering transformation, pro-groupoid, Čech fundamental pro-groupoid, covering reduced sieve, locally constant presheaf, category of fractions, subdivision, fundamental groupoid, Čech fundamental group, G-sets, continuous G-sets

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Pages:
1-31
Main language of publication
English
Received
1995-05-30
Accepted
1997-05-14
Published
1998
Exact and natural sciences