Alphabeta Math
False statementConstruction: AI-adaptedVerification: AI-generatedprecheck passaudited 2026-09-01 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: every abelian category has enough projectives and enough injectives

Statement

False. Every abelian category has enough projectives and enough > injectives.

Facts & Assumptions

Given: The abelian category FinAb of finite abelian groups.

[L1]

Enough projectives and enough injectives are extra hypotheses, not part of the definition of abelian category (A category with enough projectives and with enough injectives).

[L2]

The projective-resolution construction on this page still needs a chosen projective epimorphism at each stage (A chosen chain of projective epimorphisms gives a projective resolution).

[L3]

The Grothendieck theorem gives enough injectives only under additional Grothendieck hypotheses (Every Grothendieck category has enough injectives, and every object admits an injective resolution).

Refutation

technique · direct
1.1

The category FinAb is abelian. If it had enough projectives in the sense of [L1], then some nonzero projective object P would surject onto Z/pZ for some prime p. Choose a cyclic quotient u:PZ/pmZ with m maximal among all cyclic p-power quotients of P.

L1choose
2.1

The canonical quotient q:Z/pm+1ZZ/pmZ is epic. If P were projective, u would lift across q, producing a surjection PZ/pm+1Z, contradicting maximality of m. So FinAb does not have enough projectives, and the universal statement is false. The positive statements [L2] and [L3] are therefore extra-hypothesis results, not automatic consequences of abelianity.

L2L3step 1.1algebra

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

10 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