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2007.14496

Uniform continuity of entropy on the regular points endowed with f̄

Tomasz Downarowicz, Dominik Kwietniak, Martha Łącka

correctmedium confidence
Category
Not specified
Journal tier
Specialist/Solid
Processed
Sep 28, 2025, 12:55 AM

Audit review

The paper proves uniform continuity of the entropy map on frequency-typical sequences for the f̄ and d̄ pseudometrics via a careful, block-level (all lengths) construction using finitary isomorphisms and an induced-partition/Abramov-type argument, with precise O(ε) entropy estimates (Theorem 3.3 and Theorems 1.3–1.4) . The candidate solution only controls single-letter marginals via the LCS-based bound and then incorrectly asserts |h(X)−h(Y)| ≤ |H(law(X0))−H(law(Y0))|. This inequality is false in general; equal one-letter marginals can coexist with vastly different entropy rates (e.g., a Bernoulli(1/2) i.i.d. process vs. a 2-periodic process). The key mistake is replacing block-entropy control with single-letter control and reversing an inequality in the subadditivity/infimum step. Hence the model’s proof is invalid.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The paper presents a direct, elementary proof of uniform continuity of entropy under the f̄ and d̄ pseudometrics on frequency-typical sequences, removing ergodicity assumptions and avoiding SMB and auxiliary metrics on the process space. The construction via zero-padding, joinings, and induced partitions is sound and well-motivated, and the appended proof of the Abramov formula adds value. Some expository enhancements could further streamline the argument.