Avalanches and phase transitions

Article By:

Sharoni, Amos Department of Physics, University of California, San Diego, California.

Last reviewed:2010

DOI:https://doi.org/10.1036/1097-8542.YB100187

Many systems change from one phase to another as a function of some external parameter. For example, in boiling, liquid changes to gas as a function of temperature or pressure. The transition can occur continuously or abruptly from a starting phase, through an intermediate or a mixed phase (both phases coexisting), until reaching the final phase. In the boiling example, the transition as a function of temperature will be abrupt, with more and more liquid turning to gas at the transition temperature until there is only gas and the transition ends. In recent decades, a growing number of examples have been found of systems in which the transition behaves differently. In such systems, while the relevant parameter is changing, there are many occurrences in which a discrete “amount” of one phase changes suddenly to the other in what is called an avalanche event. One can find characteristics that are universal across different systems that have a phase transition through avalanches and do not depend on the detailed mechanism of the phase transition. The avalanches span a broad range of sizes and show a power-law distribution of avalanche magnitude; that is, there are many small avalanches, fewer medium-size ones, and only a few big avalanches. This behavior appears also in complex systems that do not possess a phase transition at all, pointing toward an even more general behavior of complex systems. Transitions through avalanches are also referred to as crackling phenomena.

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