Alphabeta Math
False statementConstruction: AI-adaptedVerification: AI-generatedSession-authored (Fable 5 assisted)precheck passaudited 2026-08-28 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: pullbacks preserve epimorphisms in every category with pullbacks

Statement

In every category with pullbacks, the pullback of an epimorphism is again an epimorphism.

Facts & Assumptions

Given: The full subcategory of Hausdorff spaces and continuous maps.

[L1]
[L3]

The rationals are dense in R, and the irrationals are nonempty (Both Q and RQ are dense in R, and every nonempty open subset of R is uncountable).

Refutation

1.1

Let i:QRR be the inclusion of the rationals into the real line, regarded as Hausdorff spaces. By [L3], QR is dense in R, so [L2] says that i is epic: any two continuous maps out of R into a Hausdorff space that agree on QR are equal.

L1L2L3
2.1

Choose an irrational point xR using [L3], and let j:{x}R be the inclusion. The pullback of i along j is the map {x}, because {x}QR=. Let D={0,1} with the discrete topology, which is Hausdorff by [L1]. The two constant maps {x}D are distinct, but their composites with {x} are equal. So the pullback map is not epic, and the universal statement is false.

L1L2L3step 1.1

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

33 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