Lean-checked candidate against the φ-mixing CLT

GPT-6 Astra constructed a strictly stationary, centered φ-mixing sequence with finite second moments and divergent partial-sum variance. Along a subsequence, its variance-normalized sums converge to zero in probability rather than to a standard normal law.

Sources for this record

What was already known

Ibragimov posed the unrestricted central limit claim in 1971; Iosifescu later proposed a stronger invariance principle. Prior positive results required an additional variance condition.

AI involvement AI-led

The repository credits GPT-6 Astra with the rare-spike and feedback construction and Lean disproof under Tom Adamczewski’s direction. It does not document a named human explanation or completed human proof check.

The repository explicitly attributes the central construction and Lean disproof to GPT-6 Astra, under Adamczewski’s direction; no no-human-input session is documented.

Importance Major

If the formal statement matches the historical hypotheses, the construction refutes the longstanding CLT claim and, by implication, the stronger invariance claim.

Limitations

Lean checks the formal disproof of the CLT part, not a separate invariance-principle statement. The source calls the result a candidate; its machine-written statement-faithfulness analysis lacks independent human review or a reproduced kernel run.

Technical verification Formal (Lean 4.27.0 default kernel with Formal Conjectures and pinned Mathlib; axiom audit)

The recorded verifier accepted the exact parts.i disproof with Lean’s default kernel and only standard axioms; a source-provided statement audit maps the formal hypotheses to the classical CLT. This is reported machine verification, awaiting independent replay and expert review.

Formal checking

Recorded Lean default-kernel and comparator acceptance with standard axioms for parts.i; exact dependencies were not replayed here.

Checker
Lean 4 default kernel and recorded comparator verifier
Scope
Formal Conjectures parts.i CLT disproof
Basis
Reported by the linked checker
Evidence source

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

Human understanding Few

Default for missing human explanation: the detailed mechanism and formalization audit are machine-written, and no named human probabilist explains or endorses the central feedback/rare-spike mechanism.

Correction and publication history

2026-10-18 · publication

One formal CLT counterexample across two directory entries; the stronger invariance statement follows only by implication and is not separately formalized.

Read this published revision