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arXiv 0907.2791cond-mat.stat-mechcond-mat.soft
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涨落-耗散关系:如何比较关联函数和响应?

The fluctuation-dissipation relation: how does one compare correlation functions and responses?

D. Villamaina, A. Baldassarri, A. Puglisi, A. Vulpiani

摘要:

我们讨论了著名的爱因斯坦和久保涨落耗散关系(FDR)在更广泛的框架下的广义FDR的系统与平稳的概率分布。一个多变量线性朗之万模型,其中包括动态与记忆,被用来作为一个可处理的例子,以显示如何通常的关系,只有在特定的情况下恢复。这项研究带来了前面的模糊性检查的FDR做不知道的重要程度的自由和他们的耦合。一个类似的情况出现在动力学稀释动摇粒状介质。在那里,粒子的位置和速度之间的相关性,由于空间的不均匀性,诱导违反通常的FDR。寻找能够恢复FDR的适当的关联函数比定义"非平衡“或"有效温度”更有见地。

英文摘要:

We discuss the well known Einstein and the Kubo Fluctuation Dissipation Relations (FDRs) in the wider framework of a generalized FDR for systems with a stationary probability distribution. A multi-variate linear Langevin model, which includes dynamics with memory, is used as a treatable example to show how the usual relations are recovered only in particular cases. This study brings to the fore the ambiguities of a check of the FDR done without knowing the significant degrees of freedom and their coupling. An analogous scenario emerges in the dynamics of diluted shaken granular media. There, the correlation between position and velocity of particles, due to spatial inhomogeneities, induces violation of usual FDRs. The search for the appropriate correlation function which could restore the FDR, can be more insightful than a definition of ``non-equilibrium'' or ``effective temperatures''.

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