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2206.01055

Quasi–periodic motions in generic nearly–integrable mechanical systems

L. Biasco, L. Chierchia

correctmedium confidence
Category
Not specified
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper’s note states Theorem 1 exactly as the model proves it—namely, for H(y,x;ε)=|y|^2/2+ε f(x) with f in the generic class P^n_s, the complement of maximal KAM tori has measure ≤ c ε |log ε|^{11n+4}—and outlines the same mechanism: resonance decomposition, pendulum-type normal forms near simple resonances, control of double resonances, and a quantitative KAM step relying on Kolmogorov non-degeneracy in action–angle variables for the secular Hamiltonian H_k. The model’s solution reproduces this standard pipeline, including the role of the P^n_s hypotheses (Morse with distinct critical values and a lower bound on high modes) and the optimization K~const·|log ε|/s, yielding the stated measure bound. Differences are present only in level of detail (the paper is a short note pointing to a 101-page preprint) and in bookkeeping constants; conceptually and technically, they are aligned.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

A concise note announcing a sharp quantitative KAM result: the non–KAM set in generic analytic mechanical systems has measure O(ε|log ε|\^{11n+4}). The approach—resonance decomposition, pendulum reduction near simple resonances, non–degeneracy in action variables, and quantitative KAM—matches the field’s best techniques, and the result aligns with longstanding expectations. Minor additions to guide readers through the exponent bookkeeping and the role of the genericity class would enhance clarity.