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2409.06005

Almost automorphic subshifts with finiteness conditions for the boundary of the separating cover

Daniel Sell, Franziska Sieron

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

Audit review

The solver’s target is exactly Theorem 5.2 in the paper: under the isolation hypothesis for a value (ω,a), construct a sliding block factor Ψ of a non-periodic Toeplitz subshift X_x with the same odometer and with B_Ψ(X) = {ω}. The paper proves this by selecting long words U using Lemma 5.1 and a two-symbol code that marks precisely the occurrences tied to ω, then establishing Ω′ = Ω via divisibility in both directions and pinning down the boundary using equations (6) and (7) (Theorem 5.2 and its proof). The candidate solution achieves the same conclusion via a different local rule (“exception + default”) that reads a fixed p_{l2}-periodic coordinate j0 and overrides it only along the ω-cylinder when the central letter equals a. Minor gaps (address recognizability from a window and a brief justification that the period structure remains the same) can be filled using the paper’s Lemma 5.1 and the odometer-factor argument in the proof of Theorem 5.2, so the model’s method is sound and distinct in construction while yielding the same result. See Theorem 5.2 and the surrounding discussion of the odometer factor and equations (6)–(7) in the paper for the canonical proof and all needed lemmas, including the definition of π_x and address alignment (Proposition 2.3) and the factor-odometer relationship (Proposition 2.1) as summarized in Section 2.2.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The result addresses a natural and useful realization problem for Toeplitz factors: under an isolation hypothesis on a boundary value pair, one can produce a factor with the same odometer and a singleton boundary. The proof in the paper is clean and leverages a well-chosen uniqueness lemma on long words; the factor-odometer equality is handled elegantly through divisibility of period structures. The model’s alternative construction shows the robustness of the phenomenon. I recommend minor revisions mainly to expand a few explanatory passages (e.g., on the role of Lemma 5.1 and on the odometer equality step) and to sharpen cross-references to the preliminaries.