EHD INSTABILITIES IN NEMATICS DRIVEN BY DICHOTOMOUS NOISE - STABILITY-CRITERIA AND INFLUENCE OF FREE-BOUNDARY CONDITIONS

Different criteria for the onset of EHD instabilities in nematic liquid crystals driven by dichotomous stochastic electric fields are compared within a 1 d linear model. Sample stability gives always higher, energetic stability always lower thresholds than the first moment's stability investigated in a previous paper, showing the same qualitative behaviour. Especially the direct transition towards chaos above a critical strength of the noise and the change from stabilizing to destabilizing effect of the noise with increasing correlation time can be explained. The influence of free boundary conditions is investigated analyzing first moment's stability of a 2 d linear model. The thresholds are slightly higher but behave qualitatively like in the 1 d model. The Williams strip pattern becomes more narrow both with increasing strength and mean frequency of the noise. © 1990 Springer-Verlag.