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DY: Dynamik und Statistische Physik

DY 34: Poster

DY 34.71: Poster

Montag, 7. März 2005, 15:30–18:00, Poster TU D

Roll drift within a localized electroconvection pattern — •Dan Spiegel — Trinity University (USA)

We have found that a locally supercritical electroconvection region can be generated in a nematic liquid crystal (MBBA) by an absorbed laser beam. If a cylindrical lens is used to extend the laser cross-section into a high-aspect-ratio rectangle with the long side parallel to the director, then the locally supercritical region is essentially one dimensional. In contrast to traditional MBBA electroconvection patterns with spatially extended rolls, the localized rolls drift with frequencies on the order of 0.1 Hz. The drift frequency displays a quadratic dependence on the voltage across the sample if both the amplitude and frequency of the applied voltage are increased in a manner that keeps the pattern amplitude constant. We will discuss a possible model for these dynamics based on a Ginzburg-Landau equation in which the parameters are functions of position.