Alphabeta Math
TheoremStatement: Literature-sourcedProof: AI-adaptedPipeline-generatedjudge pass (gpt-5.6-terra)audited 2026-09-14
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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.
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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 ω, is not well-orderable, and AC fails.

Facts & Assumptions

Given: An ambient ZFA+AC model with countably infinite atom set A, full permutation group, and finite-support filter.

[F2]

Dedekind infinitude is equivalent to a countable subset relates injections from ω to Dedekind infinitude without AC.

[F3]

The well-ordering theorem gives AC implies well-orderability.

Proof

1.1F1

Let B⊆A in the model and let finite E support it. If two atoms a,b∉E had different membership in B, their transposition would fix E but move B. Thus either no atom outside E lies in B, making B finite, or every atom outside E lies in B, making it cofinite.

2.1F2step 1.1

The set A is infinite because every ground finite subset omits an atom. If f:ω→A 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.

3.1F3∎

If a well-order < of A had finite support E, the nonempty invariant set A∖E would have a least member a. Choose b∉E∪{a} and transpose a,b. The transposition fixes < and E, so must send its uniquely least outside-E member to itself, but sends a to b, contradiction. Thus A 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