Condensed Matter Theory

Abstract:

A new method of dynamically controlling the boundary conditions of a nematic liquid crystals was studied using surface flexoelectric effect. Switching between the states occurs when the movement of the surface directors rotates those in the bulk, which are then able to create or annihilate defects. The results showed that the driving force that causes the switching is a surface flexoelectric effect.

Abstract:

We study the geometry dependence of the Casimir energy for deformed metal plates by a path integral quantization of the electromagnetic field. For the first time, we give a complete analytical result for the deformation induced change in Casimir energy delta E in an experimentally testable, nontrivial geometry, consisting of a flat and a corrugated plate. Our results show an interesting crossover for delta E as a function of the ratio of the mean plate distance H, to the corrugation length lambda: For lambda<>H.

Abstract:

In this paper we study a simple spin model which has a non-interacting Hamiltonian but constrained dynamics. The model, which is a simplification of a purely topological cellular model (Davison L and Sherrington D 2000 J. Phys. A: Math. Gen. 338615, Aste T and Sherrington D 1999 J. Phys. A: Math. Gen. 32 7049), displays glassy behaviour, involves activated processes and exhibits two-step relaxation. This is a consequence of the existence of annihilation-diffusion processes on two distinct timescales, one temperature independent and the other an exponential function of inverse temperature. In fact, there are several such inter-coupled microscopic processes and great richness therein. Two versions of the model are considered, one with a single absorbing ground state and the other with a highly degenerate ground state. These display qualitatively similar but quantitatively distinct macroscopic behaviour and related, but different, microscopic behaviour. © 2001 IOP Publishing Ltd.