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We give here some examples of non pointed protomodular categories $\mathbb C$ satisfying a property similar to the property of representation of actions which holds for the pointed protomodular category $Gp$ of groups: any slice category of $Gp$, any category of groupoids with a fixed set of objects, any essentially affine category. This property gives rise to an internal construction of the center of any object $X$, and consequently to a specific characterization of the abelian objects in $\mathbb C$.
@article{TAC_2006_16_a1, author = {Dominique Bourn}, title = {Action groupoid in protomodular categories}, journal = {Theory and applications of categories}, pages = {46--58}, publisher = {mathdoc}, volume = {16}, year = {2006}, language = {en}, url = {http://geodesic.mathdoc.fr/item/TAC_2006_16_a1/} }
Dominique Bourn. Action groupoid in protomodular categories. Theory and applications of categories, Tome 16 (2006), pp. 46-58. http://geodesic.mathdoc.fr/item/TAC_2006_16_a1/