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 basic Fraenkel model
Statement
With countably infinite atoms, the full permutation group and finite supports yield a ZFA model in which every atom subset is finite or cofinite. The atom set is infinite, admits no injection from , is not well-orderable, and AC fails.
Facts & Assumptions
Given: An ambient ZFA+AC model with countably infinite atom set , full permutation group, and finite-support filter.
Fraenkel–Mostowski permutation-model theorem gives the ZFA submodel.
Dedekind infinitude is equivalent to a countable subset relates injections from to Dedekind infinitude without AC.
The well-ordering theorem gives AC implies well-orderability.
Proof
Let in the model and let finite support it. If two atoms had different membership in , their transposition would fix but move . Thus either no atom outside lies in , making finite, or every atom outside lies in , making it cofinite.
The set is infinite because every ground finite subset omits an atom. If were injective in the model, the even-indexed range would be infinite and its complement would contain the infinite odd-indexed range, contradicting step 1.1. Hence there is no such injection, in agreement with F2.
If a well-order of had finite support , the nonempty invariant set would have a least member . Choose and transpose . The transposition fixes and , so must send its uniquely least outside- member to itself, but sends to , contradiction. Thus is not well-orderable. F3 now shows by contraposition that AC fails in the permutation model. This reductive use of AC is the only choice dependence of the conclusion.
Depends on
Used by
Dependency tree · two levels
16 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
- Jech, The Axiom of Choice, §4.3 and Problems 4.3–4.4, pp. 47–52 (standard reference, not scraped)