Berlin 2005 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 30: Spiral Formation and Feedback

DY 30.1: Hauptvortrag

Montag, 7. März 2005, 10:00–10:30, TU H3010

Evolution in complex systems: record dynamics in models of spin glasses, superconductors and evolutionary ecology. — •Henrik Jeldtoft Jensen — Department of Mathematics, Imperial College London, South Kensington campus, London SW7 2AZ, U.K.

What features characterise complex system dynamics? Drawing on analogies with equilibrium critical phenomena power laws and scale invariance of fluctuations are often taken as the hallmarks of complexity. Here we argue that slow, directed dynamics, during which the system’s properties change significantly, is fundamental. The underlying dynamics is related to slow, decelerating but spasmodic release of a generalized intrinsic strain. Time series of a number of appropriate observables can be analysed to confirm this effect. The strain arises from local frustration. As the strain is released through ’quakes’, some system variable undergoes record statistics with accompanying log-Poisson statistics for the quake event times. The talk will illustrate this scenario and its consequences through discussions of memory effects in spin glasses, the observed temperature independence of thermally activated magnetic creep in superconductors and a number of properties of biological macro evolution including the gradual decrease in the extinction rate during the last 470 million years