SPATIOTEMPORAL CHAOS IN ELECTROCONVECTION

Spatiotemporal chaos (STC) near the onset of electroconvection in a ne matic liquid crystal is reported. In samples with conductivities great er than 1 x 10(-8) per ohm per meter, STC was found to evolve by means of a supercritical Hopf bifurcation from the uniform conduction state . Because this example of STC resulted from nonlinear interactions bet ween only four modes, it provides a realistic opportunity to understan d the observed phenomena in terms of a weakly nonlinear theory in the form of four coupled complex Ginzburg-Landau equations derived from th e full equations of motion of the system. For smaller conductivities, the pattern immediately above onset consisted of localized pulses of c onvection that coexisted with the conduction state. The pulses had a u nique width in the direction perpendicular to the director (the axis p arallel to the average orientation) and had much larger and varying le ngths parallel to the director.