Alphabeta Math
RemarkRemark: Literature-sourcedProof: Not applicableaudited 2026-09-04
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.

Derived functors are well defined relative to supplied resolution data

Assume the Axiom of Dependent Choice. Derived functors are well defined here in a specific seven-part sense, and each part is now on the page rather than being collapsed into one slogan:

  1. supplied resolutions give the object assignments;
  2. comparison maps or extensions exist for each morphism (A morphism has a comparison lift between the supplied projective resolutions, A morphism has a comparison extension between the supplied injective resolutions);
  3. the induced map is independent of the chosen lift (The induced homology map is independent of the chosen comparison lift, The induced cohomology map is independent of the chosen injective comparison extension);
  4. those maps preserve identities (Left derived functors relative to supplied data are additive functors, Right derived functors relative to supplied data are additive functors);
  5. those maps preserve composition (Left derived functors relative to supplied data are additive functors, Right derived functors relative to supplied data are additive functors);
  6. changing the supplied data yields a natural isomorphism (Two supplied projective resolution data define naturally isomorphic left derived functors, Two supplied injective resolution data define naturally isomorphic right derived functors); and
  7. those change-of-data isomorphisms satisfy identity and cocycle laws (Change-of-projective-resolution isomorphisms satisfy identity and cocycle laws, Change-of-injective-resolution isomorphisms satisfy identity and cocycle laws).

What this remark does not claim is a global theorem saying that enough projectives or enough injectives canonically choose one resolution for every object. The present conclusions are relative to displayed supplied data, and two different data are compared by natural isomorphism rather than by an unstated class-sized choice.

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

34 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