## Abstract

Consider a smectic A structure in which each layer is in effect a two-dimensional fluid with its director normal to the layers. If we assume the layers to be incompressible, the integral\(
\frac{1}{a}\int_P^O {n.dr}
\) represents the number of layers crossed on going from *P* to *Q*, where *a* is the layer thickness. In a disclination-free sample this number should be independent of the path chosen so that ∇ × **n** = 0. Hence **n**. ∇ × **n** = 0 and **n** × ∇ × n = 0. In other words both twist and bend distortions are absent and only the splay term remains in the Frank free-energy expression.

### Keywords

Entropy Torque Coherence Compressibility Cyano## Preview

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## Copyright information

© Plenum Press, New York 1984