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In the mathematical fields of category theory and abstract algebra, a subquotient is a quotient object of a subobject. Subquotients are particularly important in abelian categories, and in group theory, where they are also known as sections, though this conflicts with a different meaning in category theory. For example, of the 26 sporadic groups, 20 are subquotients of the monster group, and are referred to as the "Happy Family", while the other 6 are pariah groups. A quotient of a subrepresentation of a representation (of, say, a group) might be called a subquotient representation; e.g., Harish-Chandra's subquotient theorem. ==Transitive relation== The relation »is subquotient of« is transitive. ;Proof Let groups and and be group homomorphisms, then also the composition : is a homomorphism. If is a subgroup of and a subgroup of , then is a subgroup of . We have , indeed , because every has a preimage in . Thus . This means that the image, say , of a subgroup, say , of is also the image of a subgroup, namely under , of . In other words: If is a subquotient of and is subquotient of then is subquotient of . ■ 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「Subquotient」の詳細全文を読む スポンサード リンク
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