Linear analysis of transient pattern evolution in the non-Freedericksz twist geometry

Abstract

We present a study of the evolution of the transient periodic pattern in the nematic director field reorientation in the magnetic non-Fréedericksz twist geometry. The stability of the uniform director field reorientation with respect to periodic perturbations is studied as a function of the magnetic field H, the angle α between H and the initial homogeneous nematic director n0 (H not normal to n0) and the nematic viscoelastic parameters. The results predict that for α < π/2, the amplitude of the periodic modes becomes damped after a critical time and eventually fade away and consequently does not give way to periodic inversion walls as in the Freedericksz geometry (α = π/2). Also for α < π/2, it is predicted that the selected periodic modes have progressively smaller wave vectors as the director reorients back to equilibrium. The amplitude becomes damped earlier and the wave vector of the periodic pattern decreases faster with time when the magnetic field acts away from the normal to the initial director.