Alphabeta Math
PropositionStatement: AI-adaptedProof: AI-adaptedprecheck passaudited 2026-09-05
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.

Satellites give the first derived functor

Statement

Assume the Axiom of Dependent Choice.

Let A and B be abelian categories, and let F:A→B be additive.

If A has enough projectives, F is right exact, and S=(Sn) is any universal homological delta functor equipped with a chosen natural isomorphism S0→∼F, then S1≅L1PF naturally, for every supplied projective resolution datum P on all objects of A. In this sense the first left satellite of F, defined as the degree-one term of a universal homological delta functor extending F, agrees with L1PF.

If A has enough injectives, F is left exact, and T=(Tn) is any universal cohomological delta functor equipped with a chosen natural isomorphism T0→∼F, then T1≅RI1F naturally, for every supplied injective resolution datum I on all objects of A. This is the corresponding first right satellite agreement.

Facts & Assumptions

Given: A universal delta functor extending F and the corresponding derived delta functor.

[L1]

Derived functors are universal delta functors (Derived functors are universal delta functors).

[L2]

Two universal delta functors equipped with chosen degree-zero identifications to the same functor are uniquely isomorphic (Universal delta functors extending the same degree-zero functor are uniquely isomorphic).

[L3]

Universality is the structure that defines the satellite terminology used on this page (Universal delta functor).

[L4]

The derived delta functors come with canonical degree-zero identifications to F (Left derived functors form a homological delta functor, Right derived functors form a cohomological delta functor).

Proof

technique · direct
1.1L1L2L3L4givenalgebra

In the homological case, [L1] makes (LnPF) universal and [L4] identifies its degree-zero term canonically with F. The given satellite functor S is also a universal extension of F by [L3]. Therefore [L2] yields a unique isomorphism of delta functors S→∼LPF, and its degree-one component is the asserted natural isomorphism S1≅L1PF.

2.1L1L2L3L4step 1.1∎

The cohomological case is identical with (RInF) in place of (LnPF). Its degree-one component gives the natural isomorphism T1≅RI1F.

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

26 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