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2504.00960

Sequence Entropy and Independence in Free and Minimal Actions

Jaime Gómez, Irma León-Torres, Víctor Muñoz-López

correctmedium confidence
Category
Not specified
Journal tier
Specialist/Solid
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper proves both parts via Toeplitz constructions and independence theory, with rigorous upper bounds coming from odometer fiber estimates and Proposition 2.5 (sequence entropy equals log of the largest non-diagonal IN-tuple size). The candidate solution’s lower-bound constructions are plausible, but its upper bounds are flawed: (i) it asserts an “obvious” general bound h^* ≤ log m for m-symbol subshifts without justification; and (ii) in Part (2) it uses a factor map to claim an upper bound on sequence entropy, reversing the correct monotonicity (factors cannot increase sequence entropy). It also uses this to conclude there is no IN_{n+1}, which is circular without a correct upper bound. The paper’s arguments avoid these issues and are complete.

Referee report (LaTeX)

\textbf{Recommendation:} no revision

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The paper cleanly settles the stated goals using robust tools (Toeplitz subshifts, odometers, independence theory). The constructions are explicit; upper bounds are rigorous via fiber cardinalities; and the equivalence linking sequence entropy with maximal non-diagonal IN-tuple size is leveraged well. The exposition is clear and self-contained, with a helpful preliminaries section. The results are a solid contribution to the structure theory of sequence entropy in minimal/free group actions.