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In mathematics, in particular homotopy theory, a continuous mapping :, where ''A'' and ''X'' are topological spaces, is a cofibration if it satisfies the homotopy extension property with respect to all spaces ''Y''. The name is because the dual condition, the homotopy lifting property, defines fibrations. For a more general notion of cofibration see the article about model categories. ==Basic theorems== *For Hausdorff spaces a cofibration is a closed inclusion (injective with closed image); for suitable spaces, a converse holds *Every map can be replaced by a cofibration via the mapping cylinder construction * There is a cofibration (''A'', ''X''), if and only if there is a retraction from :: :to ::, since this is the pushout and thus induces maps to every space sensible in the diagram. 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「cofibration」の詳細全文を読む スポンサード リンク
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