9423114 Lubensky This project involves theroetical investigations of three subprojects related to liquid crystals: the quasicrystalline twist-grain-boundary C phase, the shape of droplets in Langmuir films, and multiple scattering of light from liquid crystals. The twin-grain-boundary phase has recently been observed experimentally. The PI proposes to study this thoroughly, including the development of a guage theory for the Smectic-C phase that will be used to calculate dislocation energies in type II systems, an analysis of dipolar interactions, and a search for the origins of quasicrystalline lock-in. The possibility that chiral pinwheel droplets of Langmuir which have been observed recently are reproduced by effective anisotropic negative line tension favoring large perimeter and the capture of a topological defect will be investigated. The extension of diffusion-wave spectroscopy formalism to nematic liquid crystals in which multiple scattering in an anisotropic medium is produced by long-range fluctuations in the dielectric constant will be studied. %%% In this project Lubensky will continue his theoretical study of complex fluids, such as liquid crystals. He is considered a world leader in the theory of these materials. The first part involves the investigation of a phase (just recently discovered in experiments) of unique structure and symmetry which may prove to be technologically important. The second part, involving the study the shapes of droplets of molecular films, will help understand interactions within the molecules that make up monolayers, a topic of great interest to both physicists and biologists. The third part, analyzing the application of a relatively new experimental technique to liquid crystals, may provide an important tool for studying liquid crystals. It is worth noting that Lubensky has just finished his collaboration with Chaikin of a new textbook in graduate level condensed matter physics that many believe will replace the textbook currently considered the standard in this area. ***
