Alphabeta Math
LemmaStatement: AI-adaptedProof: AI-generatedPipeline-generated
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.

A probability measure on the line has no nonzero translation period

Statement

Let μ be a Borel probability measure on R. If a real number a satisfies μ(A+a)=μ(A) for every Borel set A⊆R, then a=0.

Facts & Assumptions

Given: A Borel probability measure μ on R and an a∈R such that μ(A+a)=μ(A) for every Borel set A.

[F1]

A probability measure is countably additive and has total mass one. Probability measures and probability spaces

[F2]

A+a={x+a:x∈A} is the translate of A. Translation of a subset of Rn

[F3]

The real line is a complete ordered field, hence its positive reals satisfy the Archimedean property. Dedekind-complete ordered real field, Every complete ordered field is Archimedean

Proof

Given: The objects and hypotheses in the Statement.

1.1givenF2construct

Suppose a≠0 and put ℓ=∣a∣>0. Invariance under translation by a implies invariance under translation by ℓ: when a=−ℓ, apply the given identity to A+ℓ. The half-open intervals Ik=[kℓ,(k+1)ℓ), k∈Z, partition R and are translates of I0, so they all have the same measure c=μ(I0).

2.1step 1.1F1F3contradiction

If c>0, choose a natural n>1/c by [F3]. The first n intervals are disjoint, so finite additivity gives 1≥μ(⋃k=0n−1Ik)=nc>1, a contradiction. Hence c=0.

3.1step 1.1step 2.1F1discharge-contradiction∎

Countable additivity over the partition (Ik)k∈Z now gives 1=μ(R)=∑k∈Zμ(Ik)=0, again a contradiction. Therefore a=0.

Depends on

Used by

Dependency tree · two levels

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Sources