Covering morphisms of groupoids, derived modules and a 1-dimensional Relative Hurewicz Theorem
arXiv:1012.2824
Abstract
We fill a lacuna in the literature by giving a version in dimension 1 of the Relative Hurewicz Theorem, and relate this to abelianisations of groupoids, covering spaces and covering morphisms of groupoids, and Crowell's notion of derived modules.
15 pages, xypic v2 typo corrected on p.5 re composition v3 Change of title, and one sentence repetition eliminated. v3 Diagram (11) has been corrected with the two rows interchanged