Monte Carlo simulations of liquid crystals near rough walls

The effect of surface roughness on the structure of liquid crystalline fluids near solid substrates is studied by Monte Carlo simulations. The liquid crystal is modeled as a fluid of soft ellipsoidal molecules and the substrate is modeled as a hard wall that excludes the centers of mass of the fluid molecules. Surface roughness is introduced by embedding a number of molecules with random positions and orientations within the wall. It is found that the density and order near the wall are reduced as the wall becomes rougher, i.e., the number of embedded molecules is increased). Anchoring coefficients are determined from fluctuations in the reciprocal space order tensor. It is found that the anchoring strength decreases with increasing surface roughness

Mesoscopic magnetoelectric effect in chaotic quantum dots

The magnitude of the inverse Faraday effect (IFE), a static magnetization due to an ac electric field, can be strongly increased in a mesoscopic sample, sensitive to time-reversal symmetry (TRS) breaking. Random rectification of ac voltages leads to a magnetization flux, which can be detected by an asymmetry of Hall resistances in a multi-terminal setup. In the absence of applied magnetic field through a chaotic quantum dot the IFE scale, quadratic in voltage, is found as an analytic function of the ac frequency, screening, and coupling to the contacts and floating probes, and numerically it does not show any effect of spin-orbit interaction. Our results qualitatively agree with a recent experiment on TRS-breaking in a six-terminal Hall cross.Comment: 4+ pages, 2 figures; v2-published version, small change

Raman Scattered He II λ\lambda 6545 Line in the Symbiotic Star V1016 Cygni

We present a spectrum of the symbiotic star V1016 Cyg observed with the 3.6 m Canada-France-Hawaii Telescope, in order to illustrate a method to measure the covering factor of the neutral scattering region around the giant component with respect to the hot emission region around the white dwarf component. In the spectrum, we find broad wings around H$\alpha$ and a broad emission feature around 6545${\rm \AA}$ that is blended with the [N II]$\lambda$ 6548 line. These two features are proposed to be formed by Raman scattering by atomic hydrogen, where the incident radiation is proposed to be UV continuum radiation around Ly$\beta$ in the former case and He II $\lambda$ 1025 emission line arising from $n=6\to n=2$ transitions for the latter feature. We remove the H$\alpha$ wings by a template Raman scattering wing profile and subtract the [N II] $\lambda$ 6548 line using the 3 times stronger [N II] $\lambda$ 6583 feature in order to isolate the He II Raman scattered 6545 \AA line. We obtain the flux ratio $F_{6545}/F_{6560}=0.24$ of the He II $\lambda$ 6560 emission line and the 6545 \AA feature for V1016 Cyg. Under the assumption that the He II emission from this object is isotropic, this ratio is converted to the ratio $\Phi_{6545}/\Phi_{1025}=0.17$ of the number of the incident photons and that of the scattered photons. This implies that the scattering region with H I column density $N_{HI}\ge 10^{20}{\rm cm^{-2}}$ covers 17 per cent of the emission region. By combining the presumed binary period $\sim 100$ yrs of this system we infer that a significant fraction of the slow stellar wind from the Mira component is ionized and that the scattering region around the Mira extends a few tens of AU, which is closely associated with the mass loss process of the Mira component.Comment: 12 pages, 6 figures, accepted for publication in Ap

Toward the Evidence of the Accretion Disk Emission in the Symbiotic Star RR Tel

In this paper, we argue that in the symbiotic star RR Tel the existence of an accretion disk around the hot companion is strongly implied by the characteristic features exhibited by the Raman-scattered O VI lines around 6830 \AA and 7088 \AA. High degrees of polarization and double-peaked profiles in the Raman-scattered lines and single-peak profiles for other emission lines are interpreted as line-of-sight effects, where the H I scatterers near the giant see an incident double-peaked profile and an observer with a low inclination sees single-peak profiles. It is predicted that different mass concentrations around the accretion disk formed by a dusty wind may lead to the disparate ratios of the blue peak strength to the red counterpart observed in the 6830 and 7088 features. We discuss the evolutionary links between symbiotic stars and bipolar protoplanetary nebulae and conclude that the Raman scattering processes may play an important role in investigation of the physical properties of these objects.Comment: 11 pages, 3 figures, accepted for publication in the ApJ Letter

Entropic particle transport: higher order corrections to the Fick-Jacobs diffusion equation

Transport of point-size Brownian particles under the influence of a constant and uniform force field through a three-dimensional channel with smoothly varying periodic cross-section is investigated. Here, we employ an asymptotic analysis in the ratio between the difference of the widest and the most narrow constriction divided through the period length of the channel geometry. We demonstrate that the leading order term is equivalent to the Fick-Jacobs approximation. By use of the higher order corrections to the probability density we derive an expression for the spatially dependent diffusion coefficient D(x) which substitutes the constant diffusion coefficient present in the common Fick-Jacobs equation. In addition, we show that in the diffusion dominated regime the average transport velocity is obtained as the product of the zeroth-order Fick-Jacobs result and the expectation value of the spatially dependent diffusion coefficient . The analytic findings are corroborated with the precise numerical results of a finite element calculation of the Smoluchowski diffusive particle dynamics occurring in a reflection symmetric sinusoidal-shaped channel.Comment: 9 pages, 3 figure

Probing of the Kondo peak by the impurity charge measurement

We consider the real-time dynamics of the Kondo system after the local probe of the charge state of the magnetic impurity. Using the exactly solvable infinite-degeneracy Anderson model we find explicitly the evolution of the impurity charge after the measurement.Comment: 4 pages, 1 eps figure, revte

Reply to the Comment on "Enhancement of the Tunneling Density of States in Tomonaga-Luttinger Liquids"

In their comment Fabrizio and Gogolin dispute our result of the enhancement of the tunneling density of states in a Tomonaga-Luttinger liquid at the location of a backward scattering defect [Phys. Rev. Lett. 76, 4230(1996); cond-mat/9601020]. They state that the anticommutativity of the fermion operators of the left and right moving electrons was not considered properly in the Letter. We show in the Reply that the result of the Letter can be reproduced following the Comment when its calculations are performed correctly. This clearly indicates that the question about the anticommutation relations was raised by Fabrizio and Gogolin without serious grounds.Comment: Published in PRL as a Reply to the Comment by Fabrizio and Gogolin (cond-mat/9702080

Ferrotoroidic Moment as a Quantum Geometric Phase

We present a geometric characterization of the ferrotoroidic moment in terms of a set of Abelian Berry phases. We also introduce a fundamental complex quantity which provides an alternative way to calculate the ferrotoroidic moment and its moments, and is derived from a second order tensor. This geometric framework defines a natural computational approach for density functional and many-body theories

Mutations in human dynamin block an intermediate stage in coated vesicle formation

The role of human dynamin in receptor-mediated endocytosis was investigated by transient expression of GTP-binding domain mutants in mammalian cells. Using assays which detect intermediates in coated vesicle formation, the dynamin mutants were found to block endocytosis at a stage after the initiation of coat assembly and preceding the sequestration of ligands into deeply invaginated coated pits. Membrane transport from the ER to the Golgi complex was unaffected indicating that dynamin mutants specifically block early events in endocytosis. These results demonstrate that mutations in the GTP-binding domain of dynamin block Tfn-endocytosis in mammalian cells and suggest that a functional dynamin GTPase is required for receptor-mediated endocytosis via clathrin-coated pits