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In algebra, a module homomorphism is a function between modules that preserves module structures. Explicitly, if ''M'' and ''N'' are left modules over a ring ''R'', then a function is called a module homomorphism or a ''R''-linear map if for any ''x'', ''y'' in ''M'' and ''r'' in ''R'', : : If ''M'', ''N'' are right module, then the second condition is replaced with :: The pre-image of the zero element under ''f'' is called the kernel of ''f''. The set of all module homomorphisms from ''M'' to ''N'' is denoted by Hom''R''(''M'', ''N''). It is an abelian group but is not necessarily a module unless ''R'' is commutative. The isomorphism theorems hold for module homomorphisms. == Examples == *. *For any ring ''R'', * * as rings when ''R'' is viewed as a right module over itself. * * through for any left module ''M''. * * is called the dual module of ''M''; it is a left (resp. right) module if ''M'' is a right (resp. left) module over ''R'' with the module structure coming from the ''R''-action on ''R''. It is denoted by . 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「Module homomorphism」の詳細全文を読む スポンサード リンク
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