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2010.14472

Slow entropy of some combinatorial constructions

Shilpak Banerjee, Philipp Kunde, Daren Wei

correctmedium confidence
Category
Not specified
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:55 AM

Audit review

The paper proves that for any subexponential scale there exists a rank‑two system that is weakly mixing but not mixing and has infinite lower slow entropy (Theorem 1.1), via a two‑tower cutting‑and‑stacking scheme with spacers, an independence/combinatorial uniformity lemma ensuring large Hamming separation, and explicit estimates on covering numbers; it also establishes weak mixing and failure of mixing (Proposition 3.3) and lower bounds on S(P,n,ε) along suitable subsequences (Proposition 3.4) . The candidate solution outlines essentially the same two‑tower architecture (independence blocks + Chacon‑type doping), differing mainly by positing an additional explicit “rigidity stage,” which the paper does not require. Hence both are correct, with substantially the same proof strategy.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The paper convincingly constructs a rank-two system that is weakly mixing but not mixing and has infinite lower slow entropy for any subexponential scale, thereby showing there is no general upper bound on lower slow entropy for finite-rank systems. The construction is explicit and the combinatorial lemma is well tailored. Minor clarifications about the role of the scale assumptions and a brief comparison to coding-theoretic bounds would further enhance readability.