实验颗粒堆中的OFC类行为
OFC-like Behavior in Experimental Granular Piles
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中文总结 AI 辅助
本研究通过二维颗粒系统实验，发现增加摩擦耗散使雪崩指数从1.58升至1.83，且大事件仍存在，证实了OFC类动力学在真实耗散系统中的普适性。
中文摘要 AI 辅助
尺度不变的雪崩动力学通常与临界性及普适的、稳健的尺寸指数相关联。耗散通常被认为会使系统偏离临界点，逐步抑制大事件的发生。Olami-Feder-Christensen（OFC）模型挑战了这一图景：在其非守恒情形下，雪崩尺寸指数是非普适的，且可以超过平均场值τ=3/2，而贯穿系统的事件即使在强耗散下依然存在。在此，我们表明这些看似反常的特征也在一个展示尺度不变雪崩动力学的二维颗粒系统中被实验观察到。通过增加颗粒间摩擦，从而增加耗散，雪崩尺寸指数从τ=1.58增加到τ=1.83，而上截断仍与系统尺寸成正比。我们进一步识别出实验与OFC模型在记忆效应、局域动力学以及优于随机的大事件可预测性出现方面的相似性。后者表明系统并非永久处于临界态，而是通过具有不同产生极端事件倾向的构型演化。我们的结果表明，OFC类动力学不仅仅是特定模型的反常特征，而可能为理解真实耗散系统中τ>3/2的尺度不变动力学提供一个相关框架。
英文摘要
Scale-invariant avalanche dynamics are commonly associated with criticality and robust, universal size exponents. Dissipation is generally expected to drive the system away from the critical point, progressively suppressing large events. The Olami--Feder--Christensen (OFC) model challenges this picture: in its non-conservative regime, the avalanche-size exponent is non-universal and can exceed the mean-field value $τ=3/2$, while system-spanning events persist even at large dissipation. Here, we show that these apparently anomalous features are also observed experimentally in a two-dimensional granular system displaying scale-invariant avalanche dynamics. By increasing interparticle friction, and therefore dissipation, the avalanche-size exponent increases from $τ=1.58$ to $τ=1.83$, while the upper cutoff remains proportional to the system size. We further identify similarities between experiment and the OFC model in their memory effects, local dynamics, and the emergence of better-than-random predictability of large events. The latter indicates that the system does not remain permanently critical, but instead evolves through configurations with different propensities to generate extreme events. Our results suggest that OFC-like dynamics are not merely an anomalous feature of a particular model, but may provide a relevant framework for understanding scale-invariant dynamics with $τ>3/2$ in real dissipative systems.
发表机构
- Université Lyon 1, CNRS, Institut Lumière Matière（里昂第一大学，法国国家科学研究中心，光与物质研究所）
- University of Havana（哈瓦那大学）
- University of Oslo（奥斯陆大学）
机构由 AI 辅助整理，请以论文原文为准。
