Pointwise convergence of ergodic averages for two commuting transformations

For two commuting measure-preserving maps T and S of a probability space, the bilinear averages N^-1 ∑_{n<N} f(T^n x)g(S^n x) converge almost everywhere when f∈Lp, g∈Lq, p,q∈[1,∞] and 1/p+1/q≤1. No mixing or invertibility assumption is imposed.

Sources for this record

What was already known

Norm convergence was known. Pointwise results covered special settings, including powers of one transformation and distal systems. The new argument adapts the announced OpenAI triangular-Hilbert-transform breakthrough to the general two-commuting-map problem.

AI involvement AI-led

The project records GPT-6 Astra Pro solving the problem after being asked to adapt a specific OpenAI triangular-Hilbert-transform result. Claude Opus 5.5 generated the Lean proof, with Codex cleanup. Floris van Doorn, Polona Durcik, Lenka Slavíková, Joris Roos and Christoph Thiele selected the problem/approach and authored the statement; task-only autonomy is not established.

Importance Major

Resolves the stated general pointwise-convergence problem, beyond the earlier special cases.

Limitations

The original research date is not separately documented; the statement and checking record were registered on 18 October. The blueprint and proof are model-generated; the human authors supplied the formal statement and problem/approach. Guo, Xiao and Zhang subsequently give another AI-assisted proof of the same theorem, not a check or explanation of this argument.

Technical verification Formal (Lean)

Palomar reports protected statement comparison and Lean, NanoDa and con-ron kernel acceptance on 18 October 2026. The compared theorem uses Mathlib probability, measure-preserving maps and Lp definitions; no mixing or invertibility hypothesis is added.

Formal checking

Palomar reports protected statement comparison and Lean, NanoDa and con-ron kernel acceptance on 18 October 2026. The compared theorem uses Mathlib probability, measure-preserving maps and Lp definitions; no mixing or invertibility hypothesis is added.

Checker
Palomar: Lean, NanoDa and con-ron
Scope
Almost-everywhere convergence of N^-1 sum_{n<N} f(T^n x)g(S^n x) for commuting measure-preserving maps of a probability space, p,q in [1,infinity] and 1/p+1/q<=1; only the three standard Lean axioms.
Basis
Reported by the linked checker
Check date
2026-10-18
Evidence source

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

Human understanding Few

The project identifies the human-authored statement, but no named human account explaining the model-generated central proof was established. Few is the documentation default; the later separate proof does not explain this proof.

Correction and publication history

2026-10-21 · publication

Added the sourced contribution with its stated hypotheses, AI role, prior work and checking limits.

Read this published revision