Landau-de Gennes theory of isotropic-nematic-smectic liquid crystal transitions.

We propose a Landau-de Gennes variational theory fit to simultaneously describe isotropic, nematic, smectic- A , and smectic- C phases of a liquid crystal. The unified description allows us to deal with systems in which one, or all, of the order parameters develop because of the influence of defects, external fields and/or boundary conditions. We derive the complete phase diagram of the system, that is, we characterize how the homogeneous minimizers depend on the value of the constitutive parameters.

Telephone-cord instabilities in thin smectic capillaries.

Telephone-cord patterns have been recently observed in smectic liquid-crystal capillaries. We analyze the effects that may induce them. As long as the capillary keeps its linear shape, we show that a nonzero chiral cholesteric pitch favors the Sm-A*-Sm-C* transition.