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2205.08691

Word complexity of weakly mixing rank-one subshifts

Darren Creutz

correctmedium confidence
Category
math.DS
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper proves the four claims (weakly mixing examples with lim sup p(q)/q < 1.5+ε and with p(q) < q+f(q) infinitely often; and for totally ergodic rank-one, lim sup[p(q)−1.5q]=∞ and lim inf[p(q)−q]=∞; plus optimality via totally ergodic constructions with p(q) ≤ 1.5q+f(q) eventually) as stated in its Introduction (Theorems A–D) and carried out in Sections 4–5 using explicit rank‑one constructions and detailed right‑special word counts (e.g., equations (†)–(‡) in Section 4) . By contrast, the model’s solution relies on key incorrect or unsupported steps: it asserts that total ergodicity forces infinitely many distinct spacer lengths, which is contradicted by the paper’s Proposition 2.13 showing one can represent such systems (when lim sup p(q)/q < 2) with only two spacer values 0 and d occurring infinitely often; it also invokes an unsubstantiated equivalence “weak mixing ⇔ total ergodicity” for canonically bounded rank‑one systems, whereas the paper supplies its own weak‑mixing proofs without that equivalence. Additionally, the model’s complexity bounds are argued via a heuristic density-of-s(q)=2 argument with no rigorous control of the exceptional ranges, while the paper provides precise counts at anchor lengths. Hence, while the model’s end statements mirror the paper’s theorems, its proof contains substantive errors and gaps, so the correct verdict is that the paper is correct and the model proof is not.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The paper delivers sharp results on the minimal possible linear complexity for subshifts admitting weakly mixing measures and proves optimal lower bounds for totally ergodic rank-one systems. The constructions are explicit and the combinatorial estimates are carefully executed. The exposition could benefit from small clarifications (e.g., earlier signposting of the key right-special counting lemmas and a brief roadmap connecting Sections 3–5), but the mathematical content appears correct and of solid interest to specialists in symbolic dynamics and ergodic theory.