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We introduce a notion of weakly Mal'cev category, and show that: (a) every internal reflexive graph in a weakly Mal'tsev category admits at most one multiplicative graph structure in the sense of Janelidze, and such a structure always makes it an internal category; (b) (unlike the special case of Mal'tsev categories) there are weakly Mal'tsev categories in which not every internal category is an internal groupoid. We also give a simplified characterization of internal groupoids among internal categories in this context.
@article{TAC_2008_21_a5, author = {N. Martins-Ferreira}, title = {Weakly {Mal'cev} categories}, journal = {Theory and applications of categories}, pages = {91--117}, publisher = {mathdoc}, volume = {21}, year = {2008}, language = {en}, url = {http://geodesic.mathdoc.fr/item/TAC_2008_21_a5/} }
N. Martins-Ferreira. Weakly Mal'cev categories. Theory and applications of categories, The Tholen Festschrift, Tome 21 (2008), pp. 91-117. http://geodesic.mathdoc.fr/item/TAC_2008_21_a5/