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arXiv 1901.03221cond-mat.stat-mech
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有或没有淬火的剪切流体中的相关性和力

Correlations and forces in sheared fluids with or without quenching

Christian M. Rohwer, Anna Maciolek, S. Dietrich, Matthias Krüger

摘要:

空间相关性在表征与非局部效应相关的材料性质方面起着重要作用。除其他外,它们可能引起波动引起的力量。流体中的平衡相关性提供了一个广泛研究的范例,其中它们的范围通常由相关长度限制。人们发现,在失去平衡的情况下,守恒定律会将相关性扩展到这个长度之外,从而导致代数衰变。在这种情况下,在这里,我们提出了一个系统的研究流体中的相关性和力量,同时通过淬火和剪切,非保守以及保守的Langevin型动力学。我们确定哪些方面的相关性是由于剪切,由于淬火,由于同时应用这两个,以及这些属性如何依赖于系统的相关长度和其压缩性。剪切和猝灭都导致长程相关,然而,长程相关在性质和前因上都不同,并且通过施加两种扰动而混淆。这些相关性被用来计算非平衡波动引起的剪切力的存在下,有或没有淬火,从而概括了Dean和Gopinathan提出的框架。这些力与未剪切系统中的对应力相比可以更强或更弱。一般来说,它们不指向连接被认为嵌入波动介质中的小夹杂物中心的轴线。由于淬灭或剪切似乎是可实现的各种系统与保守的粒子数,包括活性物质,我们希望这些发现是相关的实验研究。

英文摘要:

Spatial correlations play an important role in characterizing material properties related to non-local effects. Inter alia, they can give rise to fluctuation-induced forces. Equilibrium correlations in fluids provide an extensively studied paradigmatic case, in which their range is typically bounded by the correlation length. Out of equilibrium, conservation laws have been found to extend correlations beyond this length, leading, instead, to algebraic decays. In this context, here we present a systematic study of the correlations and forces in fluids driven out of equilibrium simultaneously by quenching and shearing, both for non-conserved as well as for conserved Langevin-type dynamics. We identify which aspects of the correlations are due to shear, due to quenching, and due to simultaneously applying both, and how these properties depend on the correlation length of the system and its compressibility. Both shearing and quenching lead to long-ranged correlations, which, however, differ in their nature as well as in their prefactors, and which are mixed up by applying both perturbations. These correlations are employed to compute non-equilibrium fluctuation-induced forces in the presence of shear, with or without quenching, thereby generalizing the framework set out by Dean and Gopinathan. These forces can be stronger or weaker compared to their counterparts in unsheared systems. In general, they do not point along the axis connecting the centers of the small inclusions considered to be embedded in the fluctuating medium. Since quenches or shearing appear to be realizable in a variety of systems with conserved particle number, including active matter, we expect these findings to be relevant for experimental investigations.

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