Condensed Matter Theory

Abstract:

We calculate the optical conductivity of one-dimensional Mott insulators at low energies using a field theory description. The square root singularity at the optical gap, characteristic of band insulators, is generally absent and appears only at the Luther-Emery point. We also show that only few particle processes contribute significantly to the optical conductivity over a wide range of frequencies and that the bare perturbative regime is recovered only at very large energies. We discuss possible applications of our results to quasi-one-dimensional organic conductors.

Abstract:

The effect of scattering on the information transfer rate for cell phones and wireless microwave communication devices was analyzed. The antennas in the array measures the relative phase and amplitude of the signal arriving from the particular source and then transmits with the same relative amplitude but with opposite phase. It is found that the scattering instead of decreasing the efficiency, increases the information transfer rate for wireless communication devices.

Abstract:

We describe a lattice Boltzmann algorithm to simulate liquid crystal hydrodynamics. The equations of motion are written in terms of a tensor order parameter. This allows both the isotropic and the nematic phases to be considered. Backflow effects and the hydrodynamics of topological defects are naturally included in the simulations, as are non-Newtonian flow properties such as shear thinning and shear banding. © 2001 The American Physical Society.