We have studied the frustration between ferro- and antiferro-electricity in chiral smectic C like liquid crystalline phases, which is not only fundamentally interesting but also very attractive from an application point of view. It causes temperature induced successive phase transitions as characterized by a devil's staircase and the thresholdless, hysteresis-free, V-shaped switching induced by an applied electric field. The devil's staircase indicates some type of interlayer ordering, while the V-shaped switching suggests considerably diminished tilting correlation. These two are apparently contradictory to each other, but result from the same cause, i.e. the frustration. We have first summarized experimental facts regarding subphases and successive phase transitions observed in many compounds and mixtures, which we believe are related to one another and result from the frustration. We have introduced several different theoretical explanations for these observed facts, and shown that only the axial next nearest neighbor Ising (ANNNI) model can explain almost all of the facts, provided that it is unified with the XY model appropriately. The unified model can make a comprehensive explanation in the most natural way based on the most probable molecular interactions. We have then emphasised that there are several modes regarding the V-shaped switching, because the system becomes so soft with respect to the tilting direction and sense that any additional external or internal force modifies the in-plane local director alignments. For the practically usable ones, we have emphasised the need for some type of randomization in the molecular alignment at the tip of the V and/or the switching process. In particular, the two dimensional (ideally, cylindrically symmetric) azimuthal angle distribution of local in-plane directors around the smectic layer normal is most attractive. Such a randomized state at the tip of the V is thermodynamically unique under a given condition imposed by interfaces. It stays stable even when the smectic layer structure, such as a chevron, changes with temperature. Finally, we have summarized the so-far reported compounds and mixtures for the V-shaped switching and introduced some prototypes of LCDs using them.

Optical transmittance change and stroboscopic micrographs have been obtained in homogeneously aligned thin cells of S-MHPOBC, C8H17O–--COO–COO-*CH(CH3)C6H13, and R-TFMNPOBC, C8H17O–--COO–-COO-*CH(CF3)C8H17, by varying the initial applied DC voltage stepwise into the final one across the threshold. There exist two components, fast and slow, in the transmittance change due to the phase transition from antiferroelectric SmCA * to ferroelectric SmC*. The fast component is due to the pretransitional effect. The movement of the domain boundaries is responsible for the slow component. In the transmittance change due to the transition from SmC* to SmCA *, only the slow component is observed. The movement speed is mainly determined by the difference between the final and threshold voltages.

In this note, we consider the two derivative truncation of boundary string field theory for the unstable D9-brane in type-IIA string theory. We construct multiples of the stable codimension 1 solitons that correspond to stacks of D8-branes. We find the fluctuation modes that correspond to open strings stretching between the branes, and find that their masses are consistent with the string tension. We show that these modes are localized halfway between the branes and that their width is independent of the brane separation.

Switching between two different smectic layer structures, chevron and bookshelf geometries, was observed for the first time in ferroelectric liquid crystal cells. In the absence of an electric field, a chevron layer structure is formed, as in a usual smectic C * phase. An electric field induces layer switching to a bookshelf geometry with a sharp DC threshold. Accompanying the layer switching, the projection of the director onto glass plates changes from the smectic layer normal to one of the uniform states when an electric field is applied. This optical change is equivalent to what is recognized as tristable switching.

We have shown that field-induced antiferro-ferroelectric phase transition is accompanied by reversible smectic layer switching. A layer structure without any electric field applications forms a chevron structure of the same kind as in ordinary SmC*. After the application of a field, the field-induced bookshelf structure relaxes to an obtuse chevron structure. The texture change with focal conics or zigzag defects is interpreted by taking account of the field dependence of the layer tilt angle of the chevron structure. The origin of the layer switching is also discussed on the basis of the texture change.

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We investigated the electrooptic property of the SmO* phase in 1-methylheptyl-terephthalidene-bis-aminocinnamate (MHTAC), and confirmed its antiferroelectric characteristics. We also studied the miscibility of the SmO* phase with the antiferroelectric SmCA * phase, and found that the two phases are identical.

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