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In algebraic topology, the homotopy excision theorem offers a substitute for the absence of excision in homotopy theory. More precisely, let be an excisive triad with nonempty, and suppose the pair is ()-connected, , and the pair is ()-connected, . Then the map induced by the inclusion : is bijective for and is surjective for . A nice geometric proof is given in the book by tom Dieck.〔T. tom Dieck, ''Algebraic Topology'', EMS Textbooks in Mathematics, (2008).〕 This result should also be seen as a consequence of the Blakers–Massey theorem, the most general form of which, dealing with the non-simply-connected case.〔R. Brown and J.-L. Loday, ''Homotopical excision and Hurewicz theorems for ''n''-cubes of spaces'', Proc. London Math. Soc., (3) 54 (1987) 176-192.〕 The most important consequence is the Freudenthal suspension theorem. == References == 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「Homotopy excision theorem」の詳細全文を読む スポンサード リンク
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