A sheaf FF of sets on (the category of open subsets of) a topological space XX is called flabby (or often: flasque, which is the original French term) if for any open subset U⊂XU \subset X, the restriction morphism F(X)→F(U)F(X)\to F(U) is surjective; equivalently if for any opens U⊂V⊂XU\subset V\subset X the … See more Flabby sheaves were probably first studied in Tohoku, where flabby resolutions were also considered. A classical reference is 1. Roger GodementTopologie Algébrique et Théorie des Faisceaux. Actualités Sci. Ind. No. 1252. Publ. … See more An archetypal example of a flabby sheaf is the sheaf of all set-theoretic (not necessarily continuous) sections of a bundle E→XE\to X: Since every sheaf over a topological … See more WebMay 8, 2024 · In topology, a branch of mathematics, a cosheaf with values in an ∞-category C that admits colimits 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 [math]\displaystyle{ U_i }[/math] of open subsets with union …
Cosheaf representations of relations and Dowker complexes
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WebDec 3, 2024 · The cosheaf representation of a relation actually embodies both Dowker complexes, and we construct a duality functor that exchanges the two complexes. The Dowker complex is an abstract simplicial complex that is constructed from a binary relation in a straightforward way. Although there are two ways to pe WebFeb 8, 2024 · Abstract: A cosheaf is the dual notion of a sheaf, but we cannot define its homology as the formal dual of sheaf cohomology, in general, because of the lack of the … WebApr 9, 2024 · In particular, to actually compute cosheaf homology, it's often more useful to use a resolution by flabby cosheaves, as Bredon does, but the existence of such a … ph moodle lb