False statementConstruction: AI-adaptedVerification: AI-generatedPipeline-generatedprecheck passaudited 2026-08-31‡ rests on unproved material (inherited)

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.

‡ Rests on 3 statements not proved in this library, by way of the results it cites. This item cites no such statement directly; it depends on results that do. The unproved premises it inherits are ‡ Cohen's first model: an infinite Dedekind-finite set of reals, ‡ Sierpiński 1947: the generalised continuum hypothesis implies the Axiom of Choice and ‡ The continuum hypothesis and its generalisation are independent of ZFC. Each is recorded with a citation to the literature and is not established here, because the track that would prove it has not yet been developed in this library. Everything else in this proof is proved here.

FALSE: the degreewise splitting of the cone sequence is a chain splitting

Statement

The degreewise splitting of the canonical cone sequence is automatically a chain splitting.

Facts & Assumptions

Given: The chain map $\times 2 : Z [0] \to Z [0]$ between stalk complexes concentrated in degree $0$ .

[A1]

The statement refuted is: the degreewise splitting of the canonical cone sequence is automatically a chain splitting.

[L1]

The canonical cone sequence is degreewise split short exact (The canonical mapping-cone sequence is degreewise split short exact).

[L2]

The cone of the zero map is the direct sum with a shift (The cone of the zero map is the direct sum with a shift).

[L3]

Homology of a shift is shifted homology (Homology of a shift is shifted homology).

Refutation

technique · direct

1.1

By [L1], the cone sequence for $\times 2$ is degreewise split. If it were a chain splitting as well, then the cone would be isomorphic as a complex to $Z [0] \oplus Z [1]$ as in [L2].

A1L1L2givenalgebra

2.1

But $Cone (\times 2)$ is the two-term complex $0 \to Z \overset{2}{\to} Z \to 0,$ so its homology is $H_{0} ≅ Z / 2$ and $H_{1} = 0$ , whereas $Z [0] \oplus Z [1]$ has $H_{0} ≅ Z$ and $H_{1} ≅ Z$ by [L3]. Hence no chain splitting exists, so [A1] is false.

A1L2L3step 1.1algebra∎

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

17 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

Charles A. Weibel, Chapter 1 of An Introduction to Homological Algebra (standard reference, not scraped)