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OP-5352Status unassessedDynamical systems

Furstenberg's times pp, times qq conjecture

TheoremDB P9222 · Candidate awaiting source review

Inferred from the community field; finer classification has not been reviewed.

Source candidate · not reviewedAs of 2026-09-08Source & evidence ↓

Problem statement

Let pp and qq be natural numbers with p≥2p \geq 2 and q≥2q \geq 2. Two integers p,q≥2p, q \geq 2 are called multiplicatively independent if log⁡p/log⁡q\log p / \log q is irrational. Let T\mathbb{T} denote the unit additive circle. For each natural number nn, define the map Tn:T→TT_n : \mathbb{T} \to \mathbb{T} by Tn(x)=nx(mod1)T_n(x) = nx \pmod{1}. Let μ\mu be a Borel probability measure on T\mathbb{T} that is atomless, meaning that for every measurable set AA with μ(A)>0\mu(A) > 0, there exists a measurable subset B⊆AB \subseteq A such that 0<μ(B)<μ(A)0 < \mu(B) < \mu(A). Suppose that μ\mu is measure-preserving for both TpT_p and TqT_q, meaning that μ(Tp−1(E))=μ(E)\mu(T_p^{-1}(E)) = \mu(E) and μ(Tq−1(E))=μ(E)\mu(T_q^{-1}(E)) = \mu(E) for every Borel set E⊆TE \subseteq \mathbb{T}. Prove that if pp and qq are multiplicatively independent, then μ\mu equals the Lebesgue measure on T\mathbb{T}.

Lean 4

No Lean submitted

Formal statement

Lean 4
theorem conjecture_1_3 {p q : ℕ} (hp : 2 <= p) (hq : 2 <= q) (hpq : MultiplicativelyIndependent p q)
    {μ : Measure 𝕋} [IsProbabilityMeasure μ] [MeasureTheory.IsAtomLess μ]
    (hmup : MeasurePreserving (Tn p) μ μ)
    (hmuq : MeasurePreserving (Tn q) μ μ) :
    μ = volume

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A source attachment or link is not a verified proof. The statement’s correspondence with the original question needs human review.

Proofs & verification

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Progress & source assessment

Source-reported assessment, retrieved 8 September 2026. Frontier Science has not independently reviewed this status.

Open. No signed Lean verification is attached to this problem or its selected resolution.

This record is in the source backlog; its novelty and unresolved status have not passed source review.

References
  1. [1]TheoremDB P9222 link
  2. [2]Source formal statement (not locally verified) link

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