2507.18779
Maximizing entropy for power-free languages
Vaughn Climenhaga
correcthigh confidence
- Category
- Not specified
- Journal tier
- Strong Field
- Processed
- Sep 28, 2025, 12:57 AM
- arXiv Links
- Abstract ↗PDF ↗
Audit review
The paper proves that for every d ≥ 2 and β > 12, both X^d_β and X^d_{β+} have a unique MME (Theorem 1.1) via a concrete language decomposition and a variable-length specification property on a “good” set G, together with a strict entropy gap for the prefix/suffix obstruction families Cp, Cs defined using 4-powers. This is established in Theorem 2.1 (properties (I)–(III)) and Theorem 2.3 (a general uniqueness theorem applying when (I), (II′), (III), (IV′) hold), with the key combinatorial lemmas (e.g., Lemma 3.9) verifying (III) for d ≥ 3, β ≥ 12 (T = 1) and for d = 2, β > 12 (T = 2) and the entropy gap proved by counting G4 or G8 to show h(Cp ∪ Cs) < h(X) (Section 3.3.3) . In contrast, the model asserts the problem is likely open and claims h_top(X^d_β) = log d for all β > 1, based on a loose union bound that does not respect extendability and vastly overcounts “bad” words; this contradicts the paper’s framework and is not supported by the literature on power-free languages.
Referee report (LaTeX)
\textbf{Recommendation:} minor revisions \textbf{Journal Tier:} strong field \textbf{Justification:} The manuscript gives a clear, conceptually appealing proof of uniqueness of the MME for power-free shifts in a substantial parameter regime (all d≥2, β>12; also d≥3, β=12), using a tailored weakening of specification and an explicit pressure-gap decomposition. The argument is coherent and novel in this setting, and the paper situates the result within the broader literature on specification and power-free languages. Minor presentational refinements (e.g., collecting certain technical bounds and clarifying constants) would further aid readability, but the core mathematics appears correct and valuable.