All open problems
Open problemChecked July 24, 2026

EditorialDiophantine approximation

Lonely Runner Conjecture

A geometric question about runners with distinct speeds becoming isolated on a circular track.

Mathematical statement

For nn runners with distinct constant speeds on a unit circle, each runner is at circular distance at least 1/n1/n from every other runner at some time.

Statement source: Therefore editorial statement

Statement terms: Source-specific

Editorial wording by Therefore. No statement reuse license is granted.

Statement artifacts, not proofs

These records expose exact Lean propositions and statement-only wrappers. Defining a proposition does not supply a proof of it. A placeholder-bearing target also contains no proof. Elaboration checks syntax and types; it does not certify that a formalization perfectly captures every nuance of the informal problem.

Pinned Lean formulation 1

LonelyRunnerConjecture.lonely_runner_conjecture

Canonical source
Complete statement target, proof intentionally absentLean 4
theorem lonely_runner_conjecture (n : )    (speed : Fin n ↪ ) (lonely : Fin n    Prop)    (lonely_def :       r t, lonely r t          r2 : Fin n, r2  r           dist (t * speed r : UnitAddCircle)            (t * speed r2)  1 / n)    (r : Fin n) :  t  0, lonely r t := by  sorry
Statement source
Formal Conjectures
Lean version
v4.27.0
Placeholder
Present; no proof artifact
Source evidence
Pinned source index
Fidelity review
Community formulation

References