Xu G, Vocke D, Faccio D, Garnier J, Roger T, Trillo S, Picozzi A
Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université Bourgogne Franche-Comté, F-21078 Dijon, France.
School of Engineering and Physical Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, UK.
Nat Commun. 2015 Sep 8;6:8131. doi: 10.1038/ncomms9131.
Understanding turbulent flows arising from random dispersive waves that interact strongly through nonlinearities is a challenging issue in physics. Here we report the observation of a characteristic transition: strengthening the nonlocal character of the nonlinear response drives the system from a fully turbulent regime, featuring a sea of coherent small-scale dispersive shock waves (shocklets) towards the unexpected emergence of a giant collective incoherent shock wave. The front of such global incoherent shock carries most of the stochastic fluctuations and is responsible for a peculiar folding of the local spectrum. Nonlinear optics experiments performed in a solution of graphene nano-flakes clearly highlight this remarkable transition. Our observations shed new light on the role of long-range interactions in strongly nonlinear wave systems operating far from thermodynamic equilibrium, which reveals analogies with, for example, gravitational systems, and establishes a new scenario that can be common to many turbulent flows in photonic quantum fluids, hydrodynamics and Bose-Einstein condensates.
理解由通过非线性强烈相互作用的随机色散波产生的湍流是物理学中的一个具有挑战性的问题。在此，我们报告了一个特征转变的观测结果：增强非线性响应的非局部特性会驱使系统从完全湍流状态转变，该状态以大量相干小尺度色散激波（小激波）为特征，转变为意外出现的巨大集体非相干激波。这种全局非相干激波的前沿携带了大部分随机涨落，并导致局部谱的奇特折叠。在石墨烯纳米片溶液中进行的非线性光学实验清楚地突出了这一显著转变。我们的观测结果为远离热力学平衡运行的强非线性波系统中长程相互作用的作用提供了新的见解，揭示了与例如引力系统的类比，并建立了一种可能在光子量子流体、流体动力学和玻色 - 爱因斯坦凝聚体中的许多湍流中普遍存在的新情况。
