Influence of excitation wave forms and frequencies on the fundamental time symmetry of the system dynamics, studied in nematic electroconvection

Abstract

The dynamics of periodically driven nematic electroconvection, a classical dissipative pattern forming system, is studied experimentally and theoretically. We demonstrate that for certain excitation wave forms, the system's dynamic response can be periodic with the excitation or subharmonic, depending on the periodicity of the excitation as control parameter, while for some classes of wave forms, a subharmonic response seems to be principally excluded. In particular, we describe influences of frequency and time symmetry of triangular excitation wave forms. Two intrinsically different routes for the transition to subharmonic dynamics are observed. The time characteristics of the system variables are determined by numerical solution of appropriate model equations and a Floquet analysis. Experimental data are compared to calculations of the model system of two coupled linear differential equations. Results of experiment and model are in excellent agreement.