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arXiv 1808.03255cond-mat.stat-mechnlin.CD
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混沌的临界涨落和慢化

Critical fluctuations and slowing down of chaos

Moupriya Das, Jason R. Green

摘要:

冷却到液体-蒸汽临界点的流体在密度上产生跨越系统的波动,从而改变了它们的视觉外观。尽管这个临界点有丰富的现象学,但目前还没有对潜在的机械不稳定性的解释。在分子动力学中,分子位置的结构关联如何克服确定性混沌的不稳定力?在这里,我们从非线性动力学和统计物理耦合技术来分析这种奇异状态的出现。我们的数值模拟表明,临界动力学的有序机制是直接可测量的时空李雅普诺夫模式的层次。一个子集的不稳定模式软化的临界点附近,与显着的抑制,其特征指数反映了减弱的对初始条件的敏感性。然而,在这些指数的时间波动,表现出分歧的动态时间尺度和幂律签名的关键动态。总的来说,这些结果是一个关键的放缓的混乱,坐在我们的统计理解的奇异热力学响应在液体-蒸汽临界点的根源症状。

英文摘要:

Fluids cooled to the liquid-vapor critical point develop system-spanning fluctuations in density that transform their visual appearance. Despite the rich phenomenology of this critical point, there is not currently an explanation of the underlying mechanical instability. How do structural correlations in molecular positions overcome the destabilizing force of deterministic chaos in the molecular dynamics? Here, we couple techniques from nonlinear dynamics and statistical physics to analyze the emergence of this singular state. Our numerical simulations reveal that the ordering mechanisms of critical dynamics are directly measurable through the hierarchy of spatiotemporal Lyapunov modes. A subset of unstable modes softens near the critical point, with a marked suppression in their characteristic exponents reflecting a weakened sensitivity to initial conditions. Finite-time fluctuations in these exponents, however, exhibit diverging dynamical timescales and power law signatures of critical dynamics. Collectively, these results are symptomatic of a critical slowing down of chaos that sits at the root of our statistical understanding of the singular thermodynamic responses at the liquid-vapor critical point.

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