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Higher Order Spectra of Avalanche Noise

Materials Computation Center, University of Illinois Duane D. Johnson and Richard Martin, NSF DMR-03-25939 Dynamics of Disordered Nonequilibrium Systems: Hysteresis, Noise, and Domain Wall Dynamics in Systems Ranging from Magnets to Earthquakes Karin Dahmen (UIUC, MCC-UIUC).

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Higher Order Spectra of Avalanche Noise

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  1. Materials Computation Center, University of Illinois Duane D. Johnson and Richard Martin, NSF DMR-03-25939Dynamics of Disordered Nonequilibrium Systems: Hysteresis, Noise, and Domain Wall Dynamics in Systems Ranging from Magnets to Earthquakes Karin Dahmen (UIUC, MCC-UIUC) Higher Order Spectra of Avalanche Noise Approach:Graduate student Amit Mehta developed a new scaling theory for higher order spectra of noise in systems with avalanches using mean field theory and simulations. He compared the results to new experiments done by graduate student Andrea Mills with Prof. Michael Weissman on Barkhausen noise in magnets and found good agreement in almost all aspects. Higher order spectra are useful to determine if noise in systems is due to large avalanches of flipping domains or many small domains switching back and forth. Significant results: To our knowledge this represents the first scaling theory of higher order spectra of crackling noise. The results are expected to be relevant to a large class of systems with avalanches and crackling noise, ranging from magnets, to charge density waves, to superconductors, to shape memory alloys, and possibly even to earthquakes. This work also supported by DMR 03-14279 Results for 1.5 spectra for Barkhausen Noisein mean field theory and simulations, fromMehta, Dahmen, Weissman, and Wotherspoon submitted to Physical Review Letters, 2005. Crackling Noise As iron is magnetized, its magnetic moments flip in avalanches, thereby inducing voltage pulses in the surrounding search coil. The coil can be attached to a speaker and Barkhausen Noise will be heard.

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