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RemarkRemark: Literature-sourcedProof: Not applicablePipeline-generatedjudge pass (gpt-6-sol)audited 2026-09-27
How statement and proof provenance work

The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.

  • Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
  • AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
  • AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.

These labels describe origin, not correctness: citations and verification chips remain separate evidence.

Spectral-sequence algebra is external to this pair

Remark

The Stacks Project proves the comparison between fixed-cover Čech cohomology and sheaf cohomology in the form of a spectral sequence. For a ringed space X, an open cover U of X and a sheaf F of OX-modules — in particular for the abelian sheaves on a topological space that are used here — there is a spectral sequence (Er,dr)r≥0, functorial in F, with E2p,q=Hˇp(U,Hq(F))⟹Hp+q(X,F), where Hq(F) denotes the presheaf V↦Hq(V,F) (Stacks Project, Cohomology of Sheaves, Lemma 20.11.5, tag 01ES). The acyclicity hypothesis of the Leray comparison enters there as a degeneration statement: if Hi(Ui0∩⋯∩Uip,F)=0 for all i>0 and all increasing tuples, then E2p,q=0 for q≠0, the spectral sequence degenerates at the E2 page, and its edge map is the isomorphism Hˇp(U,F)≅Hp(X,F) (ibid., Lemma 20.11.6, tag 01ET).

Nothing of this machinery is constructed or invoked on this page, and the acyclic-cover statement proved here as Leray acyclic-cover comparison does not depend on it. The comparison map itself is built here from the Čech–Godement double complex (Canonical map from fixed-cover Čech to sheaf cohomology), and the acyclic-cover statement is then obtained from Acyclic directions of the Čech–Godement double complex: the two augmentations u and w of the double complex are shown to be quasi-isomorphisms — the first from exactness of the rows, the second from the acyclicity of the columns — by filtering the total complex and applying the mapping-cone criterion, the total complex being formed on finite diagonals.

So the page replaces a spectral-sequence argument by an elementary double-complex argument, and it asserts no spectral-sequence theorem of its own: it neither constructs E2-pages, degenerate pages or convergence, nor appeals to a spectral-sequence theorem proved elsewhere. A consumer who needs the general statement of Lemma 20.11.5 — for instance for a cover that is not acyclic, where the comparison need not be an isomorphism — must take it from a homological-algebra development of spectral sequences; it is cited here only to record where the classical packaging of this comparison lives.

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Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

25 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.

Sources