Generator (category theory)

Generator (category theory)

In category theory in mathematics a generator (or separator) of a category mathcal C is an object "G" of the category, such that for any two different morphisms f, g: X ightarrow Y in mathcal C, there is a morphism h : G ightarrow X, such that the compositions f circ h eq g circ h.

Examples

* In the category of abelian groups, the group of integers mathbf Z is a generator: If "f" and "g" are different, then there is an element x in X, such that f(x) eq g(x). Hence the map mathbf Z ightarrow X, n mapsto n cdot x suffices.
* Similarly, the one-point set is a generator for the category of sets.


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