Herman's converse KAM mechanism revisited

Fuente: arXiv
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Hauptverfasser: Liu, Yi, Wang, Lin
Format: Preprint
Veröffentlicht: 2025
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author Liu, Yi
Wang, Lin
author_facet Liu, Yi
Wang, Lin
contents In his celebrated counterexample to the KAM theorem, Herman introduced a perturbation of an integrable system consisting of two components: a hyperbolic term and a bump function. He also remarked that it was unclear whether the bump function was truly necessary. In this note, we prove that the bump function is indeed necessary when more natural hyperbolic perturbations are considered. The proof of this necessity relies on an improved Siegel--Brjuno estimate and a parameter-dependent renormalization of resonances within the direct KAM method.
format Preprint
id arxiv_https___arxiv_org_abs_2512_03313
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Herman's converse KAM mechanism revisited
Liu, Yi
Wang, Lin
Dynamical Systems
In his celebrated counterexample to the KAM theorem, Herman introduced a perturbation of an integrable system consisting of two components: a hyperbolic term and a bump function. He also remarked that it was unclear whether the bump function was truly necessary. In this note, we prove that the bump function is indeed necessary when more natural hyperbolic perturbations are considered. The proof of this necessity relies on an improved Siegel--Brjuno estimate and a parameter-dependent renormalization of resonances within the direct KAM method.
title Herman's converse KAM mechanism revisited
topic Dynamical Systems
url https://arxiv.org/abs/2512.03313