Materials World Network: Crackling Noise

技术摘要：爆裂噪声是材料系统对外力的间歇性、尺度不变的反应。地球地壳被大陆漂移剪切时会在地震中破裂；纸张在被压皱时会破裂；铁在磁化时会破裂(巴克豪森噪音)；纳米线在弯曲时会破裂；骨头在断裂之前会破裂。这些系统中事件大小的广泛范围反映了浮现的标度不变性，我们使用基于重整化群理论的标度方法来理解这一点。爆裂噪声领域正在走向科学成熟，其中通用标度函数的识别和量化以及标度修正在未来的应用中将发挥核心作用。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磨练方法，以找到有效、强大的多变量标度函数来描述长程场对磁体和玻璃金属中裂纹噪声的影响，了解不同类型的浮现标度不变性之间的交叉，并在该领域测试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，他们都建议系统地分析对理论的解析、奇异和次优修正，严格评估统计和系统误差，并扩大这些强大理论的适用范围。非技术总结：许多系统在受到挤压、拉伸或扭曲时会发出爆裂的噪音。随着大陆的漂移，地壳在地震中破裂；骨头在断裂前破裂，纸张在压皱时破裂。虽然在许多实际应用中，这种噪声是一种麻烦，但在测试和预测材料故障时也是有用的。系统越小，噪声也变得越严重，对于一些纳米级系统(例如，在现代电子产品的集成电路上形成导线)，噪声可能占主导地位。当缓慢的作用力产生一系列大小不一的尖锐事件时，就会产生爆裂声。在过去的二十年里，研究人员使用统计力学的工具解释了为什么会产生爆裂噪音。在这个联合的国际项目中，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爆裂噪音的量化工具。这个跨学科的项目将使理论物理学生接触到统计力学中最先进的工具，以及工程断裂、纳米技术和微电子学中的实际材料问题。

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.