Universal frequency-preserving KAM persistence via modulus of continuity

Zhicheng Tong; Yong Li

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arXiv · 2301.13590

Universal frequency-preserving KAM persistence via modulus of continuity

Zhicheng Tong·Yong Li

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Abstract

In this paper, we study the persistence and remaining regularity of KAM invariant torus under sufficiently small perturbations of a Hamiltonian function together with its derivatives, in sense of finite smoothness with modulus of continuity, as a generalization of classical H\"{o}lder continuous circumstances. To achieve this goal, we extend the Jackson approximation theorem to the case of modulus of continuity, and establish a corresponding regularity theorem adapting to the new iterative scheme. Via these tools, we establish a KAM theorem with sharp differentiability hypotheses, which asserts that the persistent torus keeps prescribed universal Diophantine frequency unchanged and reaches the regularity for persistent KAM torus beyond H\"older's type.

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Zhicheng Tong, Yong Li. 2023-01-31. Universal frequency-preserving KAM persistence via modulus of continuity. https://arxiv.org/abs/2301.13590

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