Abstract
This paper is concerned with the algebraic structure of groupoids and crossed modules of groupoids. We describe the group structure of the automorphism group of a finite connected groupoid C as a quotient of a semidirect product. We pay particular attention to the conjugation automorphisms of C, and use these to define a new notion of groupoid action. We then show that the automorphism group of a crossed module of groupoids \(\mathcal{C}\), in the case when the range groupoid is connected and the source group totally disconnected, may be determined from that of the crossed module of groups \(\mathcal{C}_u\) formed by restricting to a single object u. Finally, we show that the group of homotopies of \(\mathcal{C}\) may be determined once the group of regular derivations of \(\mathcal{C}_u\) is known.
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Alp, M., Wensley, C.D. Automorphisms and Homotopies of Groupoids and Crossed Modules. Appl Categor Struct 18, 473–504 (2010). https://doi.org/10.1007/s10485-008-9183-y
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DOI: https://doi.org/10.1007/s10485-008-9183-y