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arXiv 1809.02158cond-mat.stat-mechcond-mat.dis-nncond-mat.quant-gasnlin.AOphysics.data-an
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高斯统计作为随机Burgers方程的涌现对称

Gaussian statistics as an emergent symmetry of the stochastic Burgers equation

Enrique Rodriguez-Fernandez, Rodolfo Cuerno

摘要:

对称性在临界系统的大尺度行为中起着重要的作用。虽然在平衡中,它们允许将渐近性分类为不同的普适性类,但在平衡之外,它们可以出现,有时出乎意料地,作为在“裸”相互作用中不明确的集体属性。在这里,我们阐明了出现的上下对称性的随机标量Burgers方程在一个和两个维度的渐近行为,表现为高斯波动的物理场的发生。高斯行为的这种鲁棒性与天真的预期相矛盾,这是由于Burgers方程和Kardar-Parisi-Zhang方程之间的详细关系--包括相同的对称性集--典型地显示了Tracy-Widom分布描述的非高斯波动。我们得出我们的结论,通过一个动态的重整化群的研究领域的统计,证实了直接评估的领域的概率分布函数从数值模拟的动力学方程。所有奇数阶累积量完全抵消,而对于大系统,过量峰度消失,确实与高斯行为一致。

英文摘要:

Symmetries play a conspicuous role in the large-scale behavior of critical systems. While in equilibrium they allow to classify asymptotics into different universality classes, out of equilibrium they can emerge, some times unexpectedly, as collective properties which are not explicit in the 'bare' interactions. Here we elucidate the emergence of an up-down symmetry in the asymptotic behavior of the stochastic scalar Burgers equation in one and two dimensions, manifested by the occurrence of Gaussian fluctuations for the physical field. This robustness of Gaussian behavior contradicts naive expectations, due to the detailed relation ---including the same set of symmetries--- between Burgers equation and the Kardar-Parisi-Zhang equation, which paradigmatically displays non-Gaussian fluctuations described by Tracy-Widom distributions. We reach our conclusions via a dynamic renormalization group study of the field statistics, confirmed by direct evaluation of the field probability distribution function from numerical simulations of the dynamical equation. All odd-order cumulants cancel exactly, while the excess kurtosis vanishes for large systems, indeed consistent with Gaussian behavior.

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