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In category theory in mathematics a family of generators (or family of separators) of a category is a collection of objects, indexed by some set ''I'', such that for any two morphisms in , if then there is some ''i∈I'' and morphism , such that the compositions . If the family consists of a single object ''G'', we say it is a generator (or separator). Generators are central to the definition of Grothendieck categories. The dual concept is called a cogenerator or coseparator. ==Examples== * In the category of abelian groups, the group of integers is a generator: If ''f'' and ''g'' are different, then there is an element , such that . Hence the map suffices. * Similarly, the one-point set is a generator for the category of sets. In fact, any nonempty set is a generator. * In the category of sets, any set with at least two objects is a cogenerator. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Generator (category theory)」の詳細全文を読む スポンサード リンク
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