Dynamical Nonlinearity in Relaxation of Spatiotemporal Chaos

The relaxation to turbulent states after the instantaneous removal of external forces that make the convective pattern ordered is examined for soft-mode turbulence, which is one of the types of experimental spatiotemporal chaos in the electroconvection of nematic liquid crystals. The soft-mode turbulence caused by the interaction of convection with the nematic director, which behaves as a Nambu–Goldstone mode, is in a spatiotemporal chaotic state concerning the orientation of the convective roll. A magnetic field that can align the orientation of the nematic director acts as an external force in this system, and its application increases the order of the orientation of the rolls. In this study, the relaxation functions of the order parameter after the instantaneous removal of the magnetic fields are measured. The relaxation functions showing a two-stage relaxation are obtained. Convective patterns are observed during the relaxation process to clarify what behaviors of the convective structures correspond to these quantitative results. The results are considered to be induced by a nonlinear process of superposition of two convective states.