Complexity from Microscopic to Macroscopic Scales: Coherence and Large Deviations

Proceedings of the NATO Advanced Study Institute, Geilo, Norway, from 17-27 April, 2001

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Many mesoscopic systems display `adaptive' behaviour - changes in some physical property that results from a small change in an internal or external driving force. There is a kind of progression in adaptive phenomena, from quantum mesoscopics to complex, evolved cooperative systems and large scale events like turbulence. The field of mesoscopic magnetism, especially quantum coherence and quantum tunnelling in spin systems, and the coupling between mesoscopic magnetism and mesoscopic transport is currently a very active area of solid state physics. `Dephasing' is an important concept in mesoscopic systems like these. A basic question is the limit at which quantum mechanics breaks down and what it can be replaced with. Another interesting crossover is that between complexity and large excursions or events, with turbulence as a prototype example. The book also contains a discussion of finance. Qualitatively speaking, turbulence and financial markets are apparently similar, so our understanding of turbulence may be relevant to understanding price fluctuations.