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 , an open cover of and a sheaf of -modules — in particular for the abelian sheaves on a topological space that are used here — there is a spectral sequence , functorial in , with where denotes the presheaf (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 for all and all increasing tuples, then for , the spectral sequence degenerates at the page, and its edge map is the isomorphism (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 and 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 -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.
Depends on
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
- The Stacks Project, Cohomology of Sheaves (standard reference, not scraped)