Thermal Fluctuations, Subcritical Bifurcation, and Nucleation of Localized States in Electroconvection

Abstract

Measurements of the mean-square amplitude of thermally-induced fluctuations of a thin layer of the nematic liquid crystal I52 subjected to a voltage V < Vc are reported. They yield the limit of stability Vc of the spatially uniform conduction state to infinitesimal perturbations. Localized long-lived convecting structures known as worms form spontaneously from the fluctuations for V well below Vc. This, as well as measurements of the lifetime of the conduction state for V < Vc, suggests a thermally-activated mechanism of worm formation; but a theory for this non-potential system is lacking.Comment: 14 pages, RevTex, 5 eps figures include