Commutative Objects, Central Morphisms and Subtractors in Subtractive Categories

We give some characterizations of commutative objects in a subtractive category and central morphisms in a regular subtractive category. In particular, we show that commutative objects, i.e., internal unitary magmas, are the same as internal abelian groups in a subtractive category and that analogously, centrality has an alternative description in terms of so-called “subtractors” in a regular subtractive category.