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2505.10051

ON ALMOST PERIODIC SOLUTIONS TO NLS WITHOUT EXTERNAL PARAMETERS

Joackim Bernier, Benoît Grébert

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

Audit review

The paper proves, for every real-entire nonlinearity f with f(0)=0, f′(0)≠0 and mild growth, the existence of nonresonant infinite-dimensional Kronecker tori (equivalently: almost periodic solutions) for the 1D periodic NLS, via a regularizing normal form and a KAM scheme with internal parameters; this is stated in Definition 1.1 and Theorem 1.2 and sketched across Sections 2–3 of the note . The model’s solution constructs such a torus for the integrable defocusing cubic NLS by global Birkhoff coordinates and a Baire-type nonresonance selection, which indeed yields a valid example within the paper’s hypothesis class (it picks f(ρ)=2ρ). Hence both are correct, but the paper establishes a much stronger, nonintegrable, parameter-free result, while the model solves only a special integrable case and (now outdatedly) remarks that the general case is open.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

This expository note concisely presents a major advance: the construction of infinite-dimensional invariant tori for periodic NLS without external parameters, beyond integrability. It clearly outlines the key innovations (regularizing normal form modulo a gauge and a KAM iteration with internal parameters) and positions the result within the KAM/PDE literature. While technical details are appropriately deferred to the full paper [BGR24], a few additional clarifications would strengthen self-containment and readability.