Generalising the étale groupoid–complete pseudogroup correspondence

Robin Cockett*, Richard Garner

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

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    We prove a generalisation of the correspondence, due to Resende and Lawson–Lenz, between étale groupoids—which are topological groupoids whose source map is a local homeomorphisms—and complete pseudogroups—which are inverse monoids equipped with a particularly nice representation on a topological space.

    Our generalisation improves on the existing functorial correspondence in four ways, and subsumes various other generalisations existing in the literature. Firstly, we enlarge the classes of maps appearing to each side. Secondly, we generalise on one side from inverse monoids to inverse categories, and on the other side, from étale groupoids to what we call partite étale groupoids. Thirdly, we generalise from étale groupoids to source-étale categories, and on the other side, from inverse monoids to restriction monoids. Fourthly, and most far-reachingly, we generalise from topological étale groupoids to étale groupoids internal to any join restriction category C with local glueings; and on the other side, from complete pseudogroups to “complete C-pseudogroups”, i.e., inverse monoids with a nice representation on an object of C. Taken together, our results yield an equivalence, for a join restriction category C with local glueings, between join restriction categories with a well-behaved functor to C, and partite source-étale internal categories in C. In fact, we obtain this by cutting down a larger adjunction between arbitrary restriction categories over C, and partite internal categories in C. Beyond proving this main result, numerous applications are given, which reconstruct and extend existing correspondences in the literature, and provide general formulations of completion processes.

    Original languageEnglish
    Article number108030
    Pages (from-to)1-79
    Number of pages79
    JournalAdvances in Mathematics
    Publication statusPublished - 3 Dec 2021


    • Etale groupoids
    • Join inverse categories
    • Join restriction categories
    • Localic and hyperconnected maps


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