Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 7: Time-delayed feedback and neural networks

DY 7.2: Vortrag

Montag, 25. Februar 2008, 16:45–17:00, A 053

Controlling noise–induced oscillations by time–delayed feedback — •Clemens von Loewenich and Hartmut Benner — Institut für Festkörperphysik, Technische Universität Darmstadt, Germany

Noise-induced oscillations have been observed in an electronic van der Pol oscillator just below the Hopf bifurcation, where the noisefree system still has a stable fixed point. In previous investigations it was shown both analytically and numerically that these oscillations can be controlled by time-delayed feedback, which allows to maximize their correlation time on variation of delay time, feedback strength and noise intensity [1,2].
The experimental implementation of this model turned out to be a rather delicate problem, in particular, to achieve a variation of the noise level over several orders of magnitude. Nevertheless we were able to confirm the main theoretical predictions: Correlation time and power spectrum were measured for different delay times and feedback strengths over a noise intensity range of about 30 dB. The power spectrum of the delayed-feedback circuit exhibits the typical multi-peak structure predicted. The correlation time, in fact, shows a dramatic feedback-induced increase which fits the theory even quantitatively.

[1] N. B. Janson et al., Phys. Rev. Lett. 93, 010601 (2004)

[2] J. Pomplun et al., Europhys. Lett. 71, 366 (2005)