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In mathematics, injective sheaves of abelian groups are used to construct the resolutions needed to define sheaf cohomology (and other derived functors, such as sheaf Ext). There is a further group of related concepts applied to sheaves: flabby (flasque in French), fine, soft (mou in French), acyclic. In the history of the subject they were introduced before the 1957 "Tohoku paper" of Alexander Grothendieck, which showed that the abelian category notion of injective object sufficed to found the theory. The other classes of sheaves are historically older notions. The abstract framework for defining cohomology and derived functors does not need them. However, in most concrete situations, resolutions by acyclic sheaves are often easier to construct. Acyclic sheaves therefore serve for computa

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  • In mathematics, injective sheaves of abelian groups are used to construct the resolutions needed to define sheaf cohomology (and other derived functors, such as sheaf Ext). There is a further group of related concepts applied to sheaves: flabby (flasque in French), fine, soft (mou in French), acyclic. In the history of the subject they were introduced before the 1957 "Tohoku paper" of Alexander Grothendieck, which showed that the abelian category notion of injective object sufficed to found the theory. The other classes of sheaves are historically older notions. The abstract framework for defining cohomology and derived functors does not need them. However, in most concrete situations, resolutions by acyclic sheaves are often easier to construct. Acyclic sheaves therefore serve for computational purposes, for example the Leray spectral sequence. (en)
  • En mathématiques, un faisceau injectif est un (en) d'une catégorie abélienne de faisceaux. Typiquement, dans la catégorie des faisceaux de groupes abéliens sur un espace topologique fixé, un faisceau est dit injectif lorsque, pour tout sous-faisceau d'un faisceau , tout morphisme injectif de dans se prolonge en un morphisme de dans . Autrement dit, le foncteur (contravariant) exact à gauche est exact. (fr)
  • 층 이론에서, 단사층(單射層, 영어: injective sheaf, 프랑스어: faisceau injectif)은 층의 범주에서의 단사 대상이다. 이를 사용하여 층 코호몰로지를 계산할 수 있다. (ko)
  • 数学におけるアーベル群の入射層(にゅうしゃそう、英: injective sheaf)は層係数コホモロジー(およびその他の導来函手、例えば Ext など)の定義に必要な分解を構成するのに用いられる。 関連する概念が適用できる層の他のクラスとして、脆弱層 (flabby sheaf), 細層 (fine sheaf), 軟弱層 (soft sheaf), 非輪状層 (acyclic sheaf) などがある。歴史的には入射層の概念は、1957年アレクサンドル・グロタンディークの「」(アーベル圏が理論を得るのに十分な入射対象を持つことを示したもの)より前には導入されていた。先に挙げたほかの層のクラスはより古いものである。コホモロジーおよび導来函手を定義するための抽象的な枠組みはそれらに必要なものではない。しかし多くの具体的な状況下では、非輪状層による分解はしばしば構成が容易であり、したがって計算目的(たとえば)では非輪状層を考える。 (ja)
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  • En mathématiques, un faisceau injectif est un (en) d'une catégorie abélienne de faisceaux. Typiquement, dans la catégorie des faisceaux de groupes abéliens sur un espace topologique fixé, un faisceau est dit injectif lorsque, pour tout sous-faisceau d'un faisceau , tout morphisme injectif de dans se prolonge en un morphisme de dans . Autrement dit, le foncteur (contravariant) exact à gauche est exact. (fr)
  • 층 이론에서, 단사층(單射層, 영어: injective sheaf, 프랑스어: faisceau injectif)은 층의 범주에서의 단사 대상이다. 이를 사용하여 층 코호몰로지를 계산할 수 있다. (ko)
  • 数学におけるアーベル群の入射層(にゅうしゃそう、英: injective sheaf)は層係数コホモロジー(およびその他の導来函手、例えば Ext など)の定義に必要な分解を構成するのに用いられる。 関連する概念が適用できる層の他のクラスとして、脆弱層 (flabby sheaf), 細層 (fine sheaf), 軟弱層 (soft sheaf), 非輪状層 (acyclic sheaf) などがある。歴史的には入射層の概念は、1957年アレクサンドル・グロタンディークの「」(アーベル圏が理論を得るのに十分な入射対象を持つことを示したもの)より前には導入されていた。先に挙げたほかの層のクラスはより古いものである。コホモロジーおよび導来函手を定義するための抽象的な枠組みはそれらに必要なものではない。しかし多くの具体的な状況下では、非輪状層による分解はしばしば構成が容易であり、したがって計算目的(たとえば)では非輪状層を考える。 (ja)
  • In mathematics, injective sheaves of abelian groups are used to construct the resolutions needed to define sheaf cohomology (and other derived functors, such as sheaf Ext). There is a further group of related concepts applied to sheaves: flabby (flasque in French), fine, soft (mou in French), acyclic. In the history of the subject they were introduced before the 1957 "Tohoku paper" of Alexander Grothendieck, which showed that the abelian category notion of injective object sufficed to found the theory. The other classes of sheaves are historically older notions. The abstract framework for defining cohomology and derived functors does not need them. However, in most concrete situations, resolutions by acyclic sheaves are often easier to construct. Acyclic sheaves therefore serve for computa (en)
rdfs:label
  • Faisceau injectif (fr)
  • Injective sheaf (en)
  • 入射層 (ja)
  • 단사층 (ko)
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