Materials World Network: Crackling Noise

技术概述：噼啪声是材料系统对外力的间歇性、尺度不变的响应。当地壳被大陆漂移剪切时，会在地震中破裂；纸揉皱时会发出噼啪声；铁在磁化时发出裂纹（巴克豪森噪声）；纳米线弯曲时会产生裂纹；骨头在断裂之前会发出噼啪声。这些系统中事件大小的广泛范围反映了涌现的尺度不变性，我们使用重整化群论支持的缩放方法来理解。噼啪噪声领域的科学研究日趋成熟，其中通用尺度函数的识别和量化以及尺度的修正在未来的应用中起着核心作用。在材料研究部的支持下，美国/意大利材料世界网络项目的研究人员将开发和改进方法，以寻找有效的，强大的多变量尺度函数来描述远程场对磁体和玻璃金属中的裂纹噪声的影响，了解不同类型的涌现尺度不变性之间的交叉，并测试该领域关于连续演化模型和晶格模型关系的基本假设。在每个项目中，他们建议系统地分析理论的分析、单一和次要修正，严格评估统计和系统错误，并扩展这些强大理论的适用范围。非技术总结：许多系统，当挤压、拉伸或扭曲时，会发出噼啪声。随着大陆漂移，地壳在地震中破裂；骨头在折断之前会发出噼啪声，纸在揉皱时也会发出噼啪声。虽然在许多实际应用中令人讨厌，但这种噪声在测试和预测材料失效时也很有用。系统越小，噪音也会变得越严重，对一些纳米级系统（例如，在现代电子产品的集成电路中形成导线）来说，噪音可能会占主导地位。当一个缓慢的力产生一系列大小不等的尖锐事件时，就会产生噼啪声。在过去的二十年里，研究人员利用统计力学的工具解释了噼啪声产生的原因。在这个联合国际项目中，他们将带领一个由来自美国和意大利的研究生和博士后组成的团队，将这种解释转化为预测和控制噼啪声的定量工具。这个跨学科的项目将使理论物理专业的学生接触到统计力学中最先进的工具，以及工程断裂、纳米技术和微电子领域的实际材料问题。

TECHNICAL SUMMARY:Crackling noise is the intermittent, scale-invariant response of materials systems to external forces. The Earth's crust crackles through earthquakes when sheared by continental drift; paper crackles when crumpled; iron crackles (Barkhausen noise) when magnetized; nanowires crackle when bent; bones crackle before they fracture. The broad range of event sizes in each of these systems reflects emergent scale invariance, which we understand using scaling methods underpinned by renormalization-group theory. The field of crackling noise is maturing scientifically, where identification and quantification of universal scaling functions and corrections to scaling are playing a central role in future applications. With support from the Division of Materials Research, the investigators in the US/Italian Materials World Network project will develop and hone methods to find effective, powerful multivariable scaling functions to describe the effects of long-range fields on crackling noise in magnets and glassy metals, to understand crossovers between different types of emergent scale invariance, and to test basic assumptions in the field about the relation of continuous evolution models and lattice models. In each project, they propose to systematically analyze analytic, singular, and subdominant corrections to the theory, rigorously assess statistical and systematic errors, and extend the realm of applicability of these powerful theories.NON-TECHNICAL SUMMARY:Many systems, when squeezed, stretched, or twisted, emit crackling noise. The earth's crust crackles through earthquakes as the continents drift apart; bones crackle before they break, paper crackles when crumpled. While a nuisance in many practical applications, this noise can also be useful in testing and predicting failure in materials. The noise also becomes more severe the smaller the system, and can be dominant for some nanoscale systems (forming wires on integrated circuits in modern electronics, for example). Crackling noise happens when a slow force produces a series of sharp events with an enormous range of sizes. In the past two decades, the investigators have explained why crackling noise arises, using tools from statistical mechanics. In this joint international project, they will lead a team of graduate students and post-docs from the US and Italy to turn this explanation into a quantitative tool for predicting and controlling crackling noise. This interdisciplinary project will expose theoretical physics students both to state-of-the art tools in statistical mechanics and to practical materials problems in engineering fracture, nanotechnology and microelectronics.