Alphabeta Math
LemmaStatement: Literature-sourcedProof: AI-adaptedPipeline-generatedjudge pass (gpt-5.6-terra)audited 2026-09-14
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.

Universal real measurability transfers to finite-dimensional Euclidean spaces

Statement

In M, every subset of Rn is Lebesgue measurable for each positive finite n.

Facts & Assumptions

Given: 1n<ω and ERn in M.

[F2]

Dyadic coding supplies coin measure and its completed Lebesgue transfer: nonterminating binary codes identify interval measure with fair-coin cylinder measure.

[F5]

AC implies DC implies countable choice: in ZF, DC implies countable choice, which supplies the precise choice hypothesis of F3.

[F6]

Lebesgue outer measure, Lebesgue measurability and Lebesgue measure are unchanged by translation: translations preserve Lebesgue measurability in every finite dimension.

Proof

1.1

Let D[0,1) consist of the reals whose canonical binary code has no eventually-1 subsequence in any residue class modulo n; its complement is the finite union of Borel null sets. Split the digits of a code in D by residue modulo n. This is a Borel bijection T:D[0,1)n with Borel inverse given by interleaving the canonical coordinate codes. A length-nk cylinder maps to the corresponding product of n dyadic intervals, each of length 2k; both sides have measure 2nk. The monotone-class extension and F2–F3 make T measure preserving on all Borel sets and send Borel null sets both ways. F3 assumes countable choice, supplied here exactly by internal DC through F4–F5; the digit map itself makes no selections.

F2F3F4F5
2.1

For arbitrary E[0,1)n, F1 makes T1(E) measurable. Completion gives Borel B0 and Borel null N0 with T1(E)B0N0. Put B=B0D and N=N0D, so both lie in the domain of T. Bimeasurability and step 1.1 give ET(B)T(N), with Borel measurable T(B) and null T(N); hence E is measurable.

F1F3step 1.1
3.1

Cover Rn by the explicitly indexed disjoint half-open cubes k+[0,1)n, kZn. For each k, the set Ek=(E(k+[0,1)n))k belongs to M and is measurable by step 2.1; F6 makes its translate Ek+k measurable. The defining closure of the Lebesgue sigma-algebra under the displayed countable union now gives E=kZn(Ek+k) measurable, with no selection of representatives. When n=1, there is one residue class, D=[0,1) for canonical non-eventually-1 codes, and T is the identity under that code, so step 2.1 is exactly F1. The case n=0 is outside the stated positive range.

F1F6step 1.1step 2.1

Depends on

Used by

Dependency tree · two levels

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Sources