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首页> 外文期刊>Physical Review X >Incoherent Fermi-Pasta-Ulam Recurrences and Unconstrained Thermalization Mediated by Strong Phase Correlations
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Incoherent Fermi-Pasta-Ulam Recurrences and Unconstrained Thermalization Mediated by Strong Phase Correlations

机译：不相互的Fermi-Gasta-Ulam复发和通过强相相关介导的无约束热化

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The long-standing and controversial Fermi-Pasta-Ulam problem addresses fundamental issues of statistical physics, and the attempt to resolve the mystery of the recurrences has led to many great discoveries, such as chaos, integrable systems, and soliton theory. From a general perspective, the recurrence is commonly considered as a coherent phase-sensitive effect that originates in the property of integrability of the system. In contrast to this interpretation, we show that convection among a pair of waves is responsible for a new recurrence phenomenon that takes place for strongly incoherent waves far from integrability. We explain the incoherent recurrence by developing a nonequilibrium spatiotemporal kinetic formulation that accounts for the existence of phase correlations among incoherent waves. The theory reveals that the recurrence originates in a novel form of modulational instability, which shows that strongly correlated fluctuations are spontaneously created among the random waves. Contrary to conventional incoherent modulational instabilities, we find that Landau damping can be completely suppressed, which unexpectedly removes the threshold of the instability. Consequently, the recurrence can take place for strongly incoherent waves and is thus characterized by a reduction of nonequilibrium entropy that violates the H theorem of entropy growth. In its long-term evolution, the system enters a secondary turbulent regime characterized by an irreversible process of relaxation to equilibrium. At variance with the expected thermalization described by standard Gibbsian statistical mechanics, our thermalization process is not dictated by the usual constraints of energy and momentum conservation: The inverse temperatures associated with energy and momentum are zero. This unveils a previously unrecognized scenario of unconstrained thermalization, which is relevant to a variety of weakly dispersive wave systems. Our work should stimulate the development of new experiments aimed at observing recurrence behaviors with random waves. From a broader perspective, the spatiotemporal kinetic formulation we develop here paves the way to the study of novel forms of global incoherent collective behaviors in wave turbulence, such as the formation of incoherent breather structures.
机译：长期和争议的Fermi-Pasta-Ulam问题解决了统计物理学的基本问题，并试图解决复发的谜团导致了许多伟大的发现，例如混乱，可叠加的系统和孤独的理论。从一般的角度来看，复发通常被认为是一种相干相敏感效应，起源于系统可加工性的性质。与这种解释相比，我们表明，一对波之间的对流对发生的新的复发现象负责，该现象是针对远离可乘性的强不相干的波浪。我们通过开发非Quilibib型动力学制剂来解释不连贯的复发，该制剂考虑了不连锁波之间的相位相关性的存在。该理论揭示了复发源于一种新颖的调制不稳定形式，这表明在随机波之间自发地产生强烈相关的波动。与传统的调制稳定性相反，我们发现Landau阻尼可以完全抑制，这意外地消除了不稳定性的阈值。因此，可以对强烈相密的波进行复发，因此表征了违反熵增长的H定理的非凝固熵的特征。在其长期演化中，该系统进入了次级湍流状态，其特征在于弛豫的不可逆过程，以平衡。在标准GIBBSIAN统计力学中描述的预期热化方差，我们的热化过程不受能量和动量保存的通常限制：与能量和动量相关的逆温度为零。这推出了先前未被约束的热化的未被承认的情景，这与各种弱分散波系统相关。我们的作品应刺激旨在观察随机波的复发行为的新实验的发展。从更广泛的角度来看，我们在这里发展的时尚动力学制剂铺平了对波动湍流中的全球非连贯性集体行为的新形式的研究，例如非连贯的呼吸结构的形成。

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