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PropositionStatement: AI-adaptedProof: AI-adaptedPipeline-generatedjudge pass (gpt-5.6-terra)audited 2026-09-12
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  • 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.
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E one is homology of the associated graded complex

Statement

There is a canonical isomorphism Ep,q1≅Hp+q(gr⁡pFC), inverse to the specified initial next-page map. If d(FpCn)⊆Fp−1Cn−1 for all p,n, then Ep,q1≅gr⁡pCp+q and d1 is the map between these graded objects induced by d.

Facts & Assumptions

Given: A filtered chain complex and integers p,q.

[F1]

α0:H(E0)→E1 is a natural isomorphism (The next page is the homology of the current page).

[F2]

E0 is the associated graded complex with its differential (E zero is the associated graded complex).

[F3]

The page differential is induced by the chain differential on its numerator (The filtered differential induces d r on the r page).

Proof

technique · direct
1.1F2

Fix p. By [F2], the terms at total degrees n are gr⁡pCn, and the differential lowers n by one while fixing p. Consequently the kernel and boundary quotient at (p,q) is exactly Hp+q(gr⁡pC).

2.1F1step 1.1

Apply the inverse of α0 from [F1] and then the identification in step 1.1. The composite is the asserted isomorphism; each factor is canonical and natural, so their composite is too.

3.1F2F3step 1.1step 2.1∎

Under the additional lowering hypothesis, the induced differential on FpCn/Fp−1Cn is zero, because the image of d lies in the denominator. Its homology is therefore the same graded object. Steps 1.1 and 2.1 identify this with E1. At the next filtration level, d(Fp−1Cn)⊆Fp−2Cn−1, so [x]↦[dx] is well defined from gr⁡pCn to gr⁡p−1Cn−1. By [F3] this is precisely d1, including when either graded object is zero.

Source notes

Weibel, Chapter 5, Construction 5.4.6 and Lemma 5.4.7, pp.133–134; Sharifi, Theorem 4.2.3, pp.91–92. Increasing homological indices are used here.

The lowering-hypothesis clause is the increasing homological translation of Stacks §12.24, Lemma 12.24.3(2). The proof here is componentwise and requires no countable direct sum.

Depends on

Dependency tree · 2 levels

Sources