Course 6 Crackling noise and avalanches: Scaling, critical phenomena, and the renormalization group

Abstract

Publisher Summary The chapter reviews the basic ideas and methods used to understand crackling noise— critical phenomena, universality, the renormalization group, power laws, and universal scaling functions. These methods and tools were originally developed to understand continuous phase transitions in thermal and disordered systems. The focus is largely on crackling noise in magnetic hysteresis, called “Barkhausen” noise, the magnetic pulses emitted from (say) a piece of iron as it is placed inside an increasing external field. Systems, when stressed or deformed slowly, respond with discrete events spanning a broad range of sizes, called “crackling noise.” The chapter also focuses on understanding the emergent behavior in crackling noise (power laws and scaling functions) by exploring the consequences of this self-similar structure. The process by which models are designed and tested by experiments using Barkhausen noise is illustrated. The chapter introduces the renormalization group, and uses it to explain universality and self-similarity in these (and other) systems. The renormalization group used to explain the power laws characteristic of crackling noise, and uses it to derive the far more powerful universal scaling functions.