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In topology, a branch of mathematics, a cosheaf with values in an ∞-category ''C'' that admits colimit is a functor ''F'' from the category of open subsets of a topological space ''X'' (more precisely its nerve) to ''C'' such that *(1) The ''F'' of the empty set is the initial object. *(2) For any increasing sequence of open subsets with union ''U'', the canonical map is an equivalence. *(3) is the pushout of and . The basic example is where on the right is the singular chain complex of ''U'' with coefficients in an abelian group ''A''. Example:〔http://www.math.harvard.edu/~lurie/282ynotes/LectureIX-NPD.pdf〕 If ''f'' is a continuous map, then is a cosheaf. == See also == *sheaf (mathematics) 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「cosheaf」の詳細全文を読む スポンサード リンク
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