## Defects in Smectic C Liquid Crystals

#### Daniel PhillipsPurdue University

If a surface stabilized liquid crystal cell is cooled from the smectic-A to the smectic-C phase its layers thin causing V-shaped (chevron like) defects to form. These sharp bends in turn create an energy barrier that has to be overcome in ferro-electric switching between equilibrium patterns. In the limit as the smectic layer thickness tends to zero, the barrier becomes infinite and ad-hoc terms have been included to overcome it. We examine a gradient flow for a mesoscopic Chen-Lubensky energy $F(\psi,\mathbf{n})$ where the order parameter $\psi$ can vanish. In this model the energy barrier does not diverge as the layer thickness becomes small. The liquid crystal can evolve between equilibrium states in such a way that the layers are allowed to melt and heal, and the cone angle can thin near the chevron tip in the process. This is joint work with Lidia Mrad.

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