MECHANISM OF TRANSITION TO A WEAK TURBULENCE IN EXTENDED ANISOTROPIC SYSTEMS

Experimental results on the mechanism of transition to defect-mediated turbulence which occurs in a narrow long strip of electroconvecting nematics are presented for the first time. The scenario consists of a secondary bifurcation from stationary convection of normal rolls (Williams domain (WD)) to tilted WD, with spontaneous parity breaking, and then a transition to spatio-temporally disordered state via defect nucleation. The central point of the mechanism presented here is the discovery of fluctuations of a soft longitudinal mode in tilted WD which together with finite transverse modes lead to the defect nucleation.