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arXiv 1701.04882nlin.PS
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统一的观点:孤立行波作为离散呼吸子及其稳定性的能量判据

A Unifying Perspective: Solitary Traveling Waves As Discrete Breathers And Energy Criteria For Their Stability

J. Cuevas-Maraver, P. G. Kevrekidis, A. Vainchtein, H. Xu

摘要:

在这项工作中,我们提供了两个互补的观点孤立行波的(谱)稳定性的哈密顿非线性动力学晶格,其中的Fermi-Pasta-Ulam和户田格是典型的例子。一个是作为一个特征值问题的一个固定的解决方案,在一个共同旅行的框架,而另一个是作为一个周期轨道模移位。我们将前者的特征值与后者的Floquet乘子联系起来,并在此基础上推导出一个基于能量的谱稳定性判据。它指出,当模型的能量(哈密顿量)$H$对波速$c$的函数依赖性改变其单调性时,波稳定性发生变化的充分(但不是必要)条件。此外,在临界速度附近的稳定性发生变化,我们提供了显式的领导阶计算的不稳定的特征值,基于在临界速度$c_0$评估的哈密顿量$H"(c_0)$的二阶导数。我们证实了这一结论与一系列的分析和数值处理的例子,并讨论了其平行最近的能量为基础的离散呼吸机的稳定性标准。

英文摘要:

In this work, we provide two complementary perspectives for the (spectral) stability of solitary traveling waves in Hamiltonian nonlinear dynamical lattices, of which the Fermi-Pasta-Ulam and the Toda lattice are prototypical examples. One is as an eigenvalue problem for a stationary solution in a co-traveling frame, while the other is as a periodic orbit modulo shifts. We connect the eigenvalues of the former with the Floquet multipliers of the latter and based on this formulation derive an energy-based spectral stability criterion. It states that a sufficient (but not necessary) condition for a change in the wave stability occurs when the functional dependence of the energy (Hamiltonian) $H$ of the model on the wave velocity $c$ changes its monotonicity. Moreover, near the critical velocity where the change of stability occurs, we provide explicit leading-order computation of the unstable eigenvalues, based on the second derivative of the Hamiltonian $H"(c_0)$ evaluated at the critical velocity $c_0$. We corroborate this conclusion with a series of analytically and numerically tractable examples and discuss its parallels with a recent energy-based criterion for the stability of discrete breathers.

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