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arXiv 2311.18367nlin.CDastro-ph.EP
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作用量域与频率域中的混沌扩散:不稳定性时间估计

Chaotic diffusion in the action and frequency domains: estimate of instability times

Gabriel Teixeira Guimarães, Tatiana Alexandrovna Michtchenko

AI总结:

本文以PCR3BP为对象,比较作用量域SEM与频率域MSD及Laskar扩散方程,证明频率域方法能可靠估计混沌扩散时间且计算效率更高。

摘要:

目的:非线性系统中的混沌扩散通常在作用量框架下进行研究。本文表明,在频率域中的研究能够良好估计相空间中混沌区域的大小,以及这些区域内部的扩散时间尺度。方法:应用传统工具,如庞加莱截面、Lyapunov指数和谱分析,我们刻画平面圆型限制性三体问题(PCR3BP)的相空间。为进行比较,我们在该问题的作用量域中应用Shannon熵方法(SEM)获得扩散系数,同时在频率域中应用均方位移(MSD)方法和Laskar扩散方程获得扩散系数。我们将由所得扩散系数定义的扩散时间尺度与Lyapunov时间以及通过直接数值积分得到的不稳定性时间进行比较。结果:用于检测混沌的传统工具往往会错误表征由慢扩散或受限扩散过程占主导的运动状态。SEM在慢混沌扩散区域表现良好,但无法刻画强混沌运动区域。基于频率的方法能够精确刻画整个相空间,并且在弱混沌和强混沌运动状态下,频率域中得到的扩散时间均与直接积分得到的不稳定性时间表现出令人满意的一致性。借助SEM获得的扩散时间无法正确匹配数值积分给出的不稳定性时间。结论:我们得出,在频率域中研究动力学不稳定性可提供可靠的扩散时间尺度估计,并且在计算时间方面也具有良好的成本效益。

英文摘要:

Purpose: Chaotic diffusion in the non-linear systems is commonly studied in the action framework. In this paper, we show that the study in the frequency domain provides good estimates of the sizes of the chaotic regions in the phase space, also as the diffusion timescales inside these regions. Methods: Applying the traditional tools, such as Poincaré Surfaces of Section, Lyapunov Exponents and Spectral Analysis, we characterise the phase space of the Planar Circular Restricted Three Body Problem (PCR3BP). For the purpose of comparison, the diffusion coefficients are obtained in the action domain of the problem, applying the Shannon Entropy Method (SEM), also as in the frequency domain, applying the Mean Squared Displacement (MSD) method and Laskar's Equation of Diffusion. We compare the diffusion timescales defined by the diffusion coefficients obtained to the Lyapunov times and the instability times obtained through direct numerical integrations. Results: Traditional tools for detecting chaos tend to misrepresent regimes of motion, in which either slow-diffusion or confined-diffusion processes dominates. The SEM shows a good performance in the regions of slow chaotic diffusion, but it fails to characterise regions of strong chaotic motion. The frequency-based methods are able to precisely characterise the whole phase space and the diffusion times obtained in the frequency domain present satisfactory agreement with direct integration instability times, both in weak and strong chaotic motion regimes. The diffusion times obtained by means of the SEM fail to match correctly the instability times provided by numerical integrations. Conclusion: We conclude that the study of dynamical instabilities in the frequency domain provides reliable estimates of the diffusion timescales, and also presents a good cost-benefit in terms of computation-time.

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