Schedule Dec 10, 2003
Control of Spatio-temporal Disorder in Parametrically Forced Surface Waves
Dr. Jay Fineberg, Hebrew University

The interactions between parametrically forced waves, excited by 2 commensurate frequencie on the surface of a fluid, yield a host of different superlattice-type patterns. These states are generated via a number of different 3--wave resonant interactions. They occur either as symmetry--breaking bifurcations of hexagonal patterns composed of a single unstable mode or via nonlinear interactions between the two primary unstable modes generated by the two forcing frequencies. Near the system's bicritical point, we find that competing nonlinear states yield a highly disordered regime in both space and time. Experimentally, we rapidly stabilize this regime to a variety of nonlinear states via open-loop control by perturbation with a third excitation frequency, whose temporal symmetry governs the temporal and spatial symmetry of the selected nonlinear state. This technique also excites rapid switching between different nonlinear states.

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