Rahbari S H E, Saberi A A, Park Hyunggyu, Vollmer J
School of Physics, Korea Institute for Advanced Study, Seoul, 130-722, South Korea.
Department of Physics, College of Science, University of Tehran, 14395-547, Tehran, Iran.
Nat Commun. 2017 Apr 10;8(1):11. doi: 10.1038/s41467-017-00022-8.
Soft particulate media include a wide range of systems involving athermal dissipative particles both in non-living and biological materials. Characterization of flows of particulate media is of great practical and theoretical importance. A fascinating feature of these systems is the existence of a critical rigidity transition in the dense regime dominated by highly intermittent fluctuations that severely affects the flow properties. Here, we unveil the underlying mechanisms of rare fluctuations in soft particulate flows. We find that rare fluctuations have different origins above and below the critical jamming density and become suppressed near the jamming transition. We then conjecture a time-independent local fluctuation relation, which we verify numerically, and that gives rise to an effective temperature. We discuss similarities and differences between our proposed effective temperature with the conventional kinetic temperature in the system by means of a universal scaling collapse.Soft particulate flows such as granular media are prone to fluctuations like jamming and avalanches. Here Rahbari et al. consider the statistics of rare fluctuations to identify an effective temperature which, unlike previous ones, is valid for packing fractions both near and far from the jamming point.
软颗粒介质包括广泛的系统，涉及非生物和生物材料中的无热耗散颗粒。颗粒介质流动的表征具有重大的实际和理论意义。这些系统的一个迷人特征是，在由高度间歇性波动主导的密集状态下存在临界刚性转变，这严重影响流动特性。在这里，我们揭示了软颗粒流中罕见波动的潜在机制。我们发现，在临界堵塞密度之上和之下，罕见波动有不同的起源，并且在堵塞转变附近受到抑制。然后，我们推测了一个与时间无关的局部波动关系，我们通过数值验证了这一关系，它产生了一个有效温度。我们通过通用标度塌缩讨论了我们提出的有效温度与系统中传统动力学温度之间的异同。诸如颗粒介质之类的软颗粒流容易出现诸如堵塞和雪崩等波动。在这里，拉巴里等人考虑罕见波动的统计数据，以确定一个有效温度，与之前的温度不同，这个有效温度对于接近和远离堵塞点的堆积分数都是有效的。
