Condensed Matter Theory

Abstract:

The interplay between electrostatic interactions and orientational correlations is studied for a model system of charged rods positioned on a chain, using Monte Carlo simulation techniques. It is shown that the coupling brings about the notion of electrostatic frustration, which in turn results in: (i) a rich variety of orientational orderings such as chiral phases, and (ii) an inherently slow dynamics characterized by stretched-exponential behavior in the relaxation functions of the system.

Abstract:

We have studied the effect of optically-induced random, anisotropic disorder on the magnetoresistance of a two-dimensional electron gas by exposing the sample to an anisotropic laser speckle pattern. Changes in the amplitude of the Shubnikov-de Haas oscillations can be explained in terms of easy and hard conductivity paths, parallel and perpendicular to the long axis of the oval speckle grains, respectively. © 2005 American Institute of Physics.

Abstract:

The structure of DNA in the nucleosome core particle is studied using an elastic model that incorporates anisotropy in the bending energetics and twist-bend coupling. Using the experimentally determined structure of nucleosomal DNA [T. J. Richmond and C. A. Davey, Nature (London) 423, 145 (2003)], it is shown that elastic correlations exist between twist, roll, tilt, and stretching of DNA, as well as the distance between phosphate groups. The twist-bend coupling term is shown to be able to capture these correlations to a large extent, and a fit to the experimental data yields a new estimate of G = 25 nm for the value of the twist-bend coupling constant.