Dynamics of Extended Non-Equilibrium Systems: Hysteresis, Electromigration, and Defect Chaos

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9419506 Sethna Collective behavior emerging on long length scales will be explored in three systems. First, the investigator will study disorder-induced nucleation of bursts associated with certain hysteresis loops and investigate innovative applications to magnetic recording which result. Second, the dynamics of large, mobile voids will be studied analytically and using realistic simulations of bulk aluminum and copper. This work will help understand failure present in microfabricated devices with high current densities. Third, chaotic states in two-dimensional systems described by partial differential equations whose topological defects move in a chaotic, turbulent manner will be studied. More general coarse-graining methods will be used to investigate phase transitions and the effects of boundaries, and to understand the nature of noise in these systems. %%% For many systems, even though the underlying physics of the interactions of the individual particles is complex, on a large scale rather simple laws can often be found. Three examples of such systems that are forced to be far from equilibrium will be investigated theoretically. First, certain systems, such as magnets, behave differently depending on whether a parameter (such as an external magnetic field) is increased or decreased. Such systems will be investigated and these results will be applied to magnetic recording. Second, the movement of voids (pockets of air) in materials such as aluminum and copper will be investigated using equations and computer simulations, with a goal to better understand failure in microfabricated devices with high currents flowing through them. Third, the behavior of chaotic noise and defects will be investigated in certain classes of two-dimensional systems, such as fluids that are forced to flow and heart muscle walls. ***