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2012.15457

TOPOLOGICAL R-PRESSURE AND TOPOLOGICAL PRESSURE OF FREE SEMIGROUP ACTIONS

Yinan Zheng, Qian Xiao

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

Audit review

The paper establishes (A) lim_{r→0} Pr = P for free semigroup actions and (B) P(f0,…,fm−1,φ) = P(f0^{-1},…,f_{m−1}^{−1},φ) when the generators are homeomorphisms. Part (A) is proved via a skew-product reduction to the single-map case together with Chen’s result and the pressure identity PD(F,g)=log m+P (citations: Theorem 1.4 statement and proof sketch; Lemma 4.1; Theorem 2.1; Theorem 1.3) . Part (B) is obtained by showing PD(F^{-1},g)=PD(F,g) for the homeomorphism F and then using the same skew-product identity on the inverse semigroup (citations: Theorem 1.5 statement and its proof) . The candidate solution’s Part (A) provides a plausible and essentially correct direct covering argument using mistake balls and a combinatorial bound. However, Part (B) asserts an exact identity d_w(x,y)=d^{inv}_{θ(w)}(f_w x, f_w y) and consequent equality of weighted spanning quantities word-by-word; this fails in general for non-commuting generators, due to the suffix/prefix convention w′≤w used to define d_w and the nontrivial conjugations that arise in g_v f_w when v≤θ(w) (see the paper’s precise definitions of d_w and w′≤w) . Thus the model’s Part (B) proof is incorrect even though the statement itself is true by the paper’s skew-product argument.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The manuscript correctly develops topological r-pressure for free semigroup actions, proves its convergence to the classical pressure as r→0 via a transparent skew-product reduction, and establishes invariance of pressure under inversion for homeomorphic generators. The results are technically sound and of interest to researchers in thermodynamic formalism for semigroup dynamics. Minor improvements in exposition (clarifying suffix/prefix conventions and citing the variational principle when asserting P(F−1,g)=P(F,g)) would enhance readability.