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2505.05369

The multi-scale KAM persistence without a scaling order for Hamiltonian systems

Weichao Qian, Yong Li, Xue Yang

incompletemedium confidence
Category
math.DS
Journal tier
Specialist/Solid
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper states a three-part KAM persistence theorem for multi‑scale Hamiltonians (Theorem 1.1) with a measure bound |bad set| = O(ϵ^{1/N}), under hypotheses (R), (K), (I), and an isoenergetic variant with a scaling factor t → 1 as ε → 0 . However, the nondegeneracy condition (R) introduces a symbol N that is never defined or used in the rank condition itself, yet it reappears in the measure bound O(ϵ^{1/N}), creating a mismatch between assumptions and claimed exponent . The proof outline via a parameterized KAM step (Proposition 2.1) is provided, but key quantitative linkages between the Diophantine threshold γ, the iteration parameters (r, K, σ, h), and the final ϵ^{1/N} measure exponent are only sketched; the Measure Estimate is described narratively without a worked derivation of the exponent N . There is also an explicit internal inconsistency: Theorem 1.1 asserts t → 1, whereas Remark 3 states t → 0 as ε → 0 , and the manuscript still contains placeholders (e.g., “Section ??”), indicating an incomplete draft. By contrast, the candidate solution gives a coherent a‑posteriori route: rescale by ε̃, invoke a Rüssmann–Łojasiewicz sublevel measure bound for resonances, choose γ ∼ √κ to match a standard analytic KAM smallness κ ≲ γ^2, and then obtain |bad set| = O(κ^{1/N}) with the correct frequency‑preservation statements (full, partial, and isoenergetic up to a factor t → 1). While concise, this argument aligns with established a‑posteriori KAM frameworks and remedies the paper’s missing definition of N by tying the exponent to the sublevel estimate.

Referee report (LaTeX)

\textbf{Recommendation:} major revisions

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The manuscript addresses a relevant multi-scale KAM problem and presents claims aligned with established theory, but key proof components are underdeveloped. The exponent N in the measure estimate is not derived from a precise nondegeneracy order; the measure estimate itself is sketched rather than proved; and there is an inconsistency in the isoenergetic remark. Draft placeholders indicate the paper is not yet camera-ready. With explicit quantitative details and corrections, the work would be suitable for a specialist journal.