Directional transience implies ballisticity

OpenAI

In every dimension d≥2, an IID uniformly elliptic nearest-neighbor random walk environment on Zᵈ with almost-sure transience in a fixed direction has an almost-sure annealed velocity that is deterministic and has positive projection in that direction.

Sources for this record

What was already known

Earlier ballisticity criteria required quantitative exit or drift assumptions. In dimension one, uniform ellipticity and transience can coexist with zero speed.

AI involvement AI-led

The released OpenAI mathematics release attributes its manuscripts and Lean library to an internal model. It gives no session record establishing full autonomy for this argument.

OpenAI institutional authorship and the released release’s model-production account support AI-led work; this manuscript has no session-level autonomy record.

Importance Notable

Resolves the Fribergh–Kious one-direction ballisticity conjecture under its stated higher-dimensional assumptions.

Limitations

The separate d≥3 positive-probability and velocity-hemisphere extension is outside this claim. The released source states a Lean proof; no named human explanation is documented.

Technical verification Formal (Lean)

The released Lean scope document and Main.lean identify a machine proof of the exact d>=2 IID uniformly elliptic almost-sure transience-to-positive-velocity statement. The comparator’s sorry is a specification placeholder; the imported OAI theorem supplies the proof. This is repository-reported formal verification.

Formal checking

Lean formalization of MainStatement via OAI.Probability.Ballisticity.Main and imported modules

Checker
Lean kernel in the OpenAI math release, as reported by repository artifacts
Scope
For d>=2 IID uniformly elliptic nearest-neighbor environments, almost-sure directional transience implies an almost-sure deterministic velocity with positive directional projection
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Few

The manuscript gives a proof narrative but no named human explanation of the new route from qualitative escape to finite regeneration duration is documented; Few is a missing-evidence default.

Correction and publication history

2026-10-18 · publication

Resolves the Fribergh–Kious one-direction ballisticity conjecture under its stated higher-dimensional assumptions.

Read this published revision