2503.03976
POINTWISE ERGODIC THEOREMS FOR NON-CONVENTIONAL BILINEAR AVERAGES ALONG (⌊n^c⌋, −⌊n^c⌋)
Leonidas Daskalakis
correcthigh confidence
- Category
- Not specified
- Journal tier
- Strong Field
- Processed
- Sep 28, 2025, 12:56 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The paper proves almost-everywhere convergence of the bilinear averages along (⌊h(n)⌋, −⌊h(n)⌋) for h in the c-regularly varying class with c in [1, 23/22) and further identifies the limit with Bourgain’s bilinear limit, see Theorem 1.7 and equation (1.9) in the uploaded PDF . Its strategy splits the averages via the inverse ϕ = h^{-1} into a main Toeplitz-weighted term that matches Bourgain’s limit (using summation by parts/Toeplitz) and an error controlled by a truncated Fourier expansion of the sawtooth Φ plus Gowers U3-norm bounds and transference; see the Strategy subsection and Section 2–4 . The candidate solution follows the same blueprint: identical change-of-variables and Toeplitz reduction for the main term; the same sawtooth truncation, oscillatory kernel analysis, and Gowers-uniformity/transference for the error. Minor deviations are bibliographic (it cites Demeter instead of Bourgain for the basic bilinear limit) and in technical presentation (L2 versus the paper’s L1-lacunary summability), but the logical path and conclusions coincide.
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions \textbf{Journal Tier:} strong field \textbf{Justification:} This work establishes the first pointwise bilinear result for deterministic sparse orbits with modulation invariance in the stated range, extending the Bourgain paradigm to (⌊h(n)⌋, −⌊h(n)⌋). The conceptual structure—Toeplitz reduction to the classical bilinear limit, sawtooth truncation, Gowers-uniformity control of oscillatory kernels, and transference—is compelling and technically well executed. The manuscript would benefit from small clarifications (especially the lacunary-to-full sequence passage and parameter bookkeeping for the choice of truncation), but I find the arguments sound and the contribution significant within ergodic theory and discrete harmonic analysis.