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2404.09348

Multifractal Analysis of F-Exponents for Finitely Irreducible Conformal Graph Directed Markov Systems

Nathan Dalaklis

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

Audit review

The paper’s main theorem (existence/uniqueness and real-analyticity of (t(ξ),q(ξ)) solving P(t,q)=qξ and ∂P/∂q=ξ; and the equalities HD(J(ξ))=HD(J1(ξ))=t(ξ)) is stated as Theorem 1.1.1 and proved in Section 4 via Proposition 4.1.1 (dimension bounds using the volume lemma) and Proposition 4.1.3 (existence/uniqueness/analyticity via convexity and the implicit function theorem), together with the derivative formulas (Lemma 2.2.1) and structure of the Manhattan region (Lemmas 2.1.2, 2.1.4) and boundary behavior (Lemma 2.2.5) . The model’s solution follows the same route: pressure regularity and derivatives, convexity/strict monotonicity, a Legendre-type minimization W(t,ξ)=P(t,q)-ξq with W_t<0 to locate t(ξ), and IFT for analyticity, then Gibbs/volume-lemma lower bound and Carathéodory-type upper bound; it also treats the comparability vs bounded F cases exactly as in the paper. Minor stylistic differences (e.g., invoking variance/Hessian identities) do not affect correctness. We find no substantive gaps: the paper ensures non-degeneracy for the IFT via strict convexity (ft,q not cohomologous to a constant) and uses SOSC to handle overlaps (hence µ(J>1)=0) .

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The manuscript establishes a clean and general multifractal spectrum formula for CGDMS under standard hypotheses (finitely irreducible, SOSC, cofinitely regular; strictly positive Hölder families). The strategy is classical and well executed: pressure regularity and convexity, a Legendre-type minimization to produce (t(ξ),q(ξ)), real-analyticity via the implicit function theorem, and matching upper/lower Hausdorff bounds using Gibbs measures and the volume lemma. The presentation is clear overall, extends known arguments to this setting, and fixes issues in earlier related work. A few clarifications would further strengthen the paper (explicitly pointing to the step ensuring ∂²P/∂q²>0 at the solution, and sharpening the discussion of the Manhattan region in the bounded case), hence a recommendation of minor revisions.