It is known that there is a wide class of path-connected topological spaces X, which are not semilocally simply-connected but have a generalized universal covering, that is, a surjective map p : X̃ → X which is characterized by the usual unique lifting criterion and the fact that X̃ is path-connected, locally path-connected and simply-connected.
For a path-connected topological space Y and a map f : Y → X, we form the pullback f∗p : f∗X̃ → Y of such a generalized universal covering p : X̃ → X and consider the following question: given a path-component Ỹ of f∗X̃, when exactly is f∗p|Ỹ : Ỹ → Y a generalized universal covering? We show that the classical criterion, of f# : π1(Y ) → π1(X) being injective, is too coarse a notion to be sufficient in this context and present its appropriate (necessary and sufficient) refinement.
Fischer, Hanspeter  1
@article{10_2140_agt_2007_7_1379,
author = {Fischer, Hanspeter},
title = {Pullbacks of generalized universal coverings},
journal = {Algebraic and Geometric Topology},
pages = {1379--1388},
year = {2007},
volume = {7},
number = {3},
doi = {10.2140/agt.2007.7.1379},
url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2007.7.1379/}
}
Fischer, Hanspeter. Pullbacks of generalized universal coverings. Algebraic and Geometric Topology, Tome 7 (2007) no. 3, pp. 1379-1388. doi: 10.2140/agt.2007.7.1379
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