ExampleConstruction: AI-generatedVerification: AI-generatedprecheck passaudited 2026-09-01

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.

The horseshoe resolution of an extension of cyclic groups

Example

For the split short exact sequence $0 \to Z / m Z \to Z / m Z \oplus Z / n Z \to Z / n Z \to 0,$ the horseshoe resolution is the direct sum of the two standard cyclic-group resolutions: $0 \to Z \oplus Z \overset{(a, b) \mapsto (m a, n b)}{\to} Z \oplus Z \to Z / m Z \oplus Z / n Z \to 0.$

Facts & Assumptions

Given: Integers $m, n \geq 1$ .

[L1]

A split short exact sequence admits the direct-sum resolution (A split short exact sequence admits the direct-sum resolution).

[L2]

The standard cyclic-group resolution is the basic side resolution (A projective resolution of a cyclic abelian group).

Verification

technique · direct

1.1givenalgebra

Exactness is checked componentwise: the kernel of the quotient map onto $Z / m Z \oplus Z / n Z$ is $m Z \oplus n Z$ , which is exactly the image of the displayed differential, and that differential is injective.

2.1L1L2step 1.1∎

The resolution in step 1.1 is the direct sum of the two side resolutions from [L2], so [L1] identifies it as the horseshoe resolution for this split extension.

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

9 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, An Introduction to Homological Algebra (standard reference, not scraped)
Romyar Sharifi, Homological Algebra (standard reference, not scraped)