Fluctuation relations for a driven Brownian particle

We consider a driven Brownian particle, subject to both conservative and non-conservative applied forces, whose probability evolves according to the Kramers equation. We derive a general fluctuation relation, expressing the ratio of the probability of a given Brownian path in phase space with that of the time-reversed path, in terms of the entropy flux to the heat reservoir. This fluctuation relation implies those of Seifert, Jarzynski and Gallavotti-Cohen in different special cases

Nonlinear Debye-Onsager-Relaxation-Effect

The quantum kinetic equation for charged particles in strong electric fields is used to derive the nonlinear particle flux. The relaxation field is calculated quantum mechanically up to any order in the applied field provided a given Maxwellian plasma. The classical limit is given in analytical form. In the range of weak fields the deformation of the screening cloud is responsible for the Debye-Onsager relaxation effect.Comment: Proceeding of the 8. International Workshop on Atomic Physics for Ion-Driven Fusion, Heidelberg 1997, appear in Laser and Particle beam

Using the de Haas-van Alphen effect to map out the closed three-dimensional Fermi surface of natural graphite

The Fermi surface of graphite has been mapped out using de Haas van Alphen (dHvA) measurements at low temperature with in-situ rotation. For tilt angles $\theta>60^{\circ}$ between the magnetic field and the c-axis, the majority electron and hole dHvA periods no longer follow the $\cos(\theta)$ behavior demonstrating that graphite has a 3 dimensional closed Fermi surface. The Fermi surface of graphite is accurately described by highly elongated ellipsoids. A comparison with the calculated Fermi surface suggests that the SWM trigonal warping parameter $\gamma_3$ is significantly larger than previously thought

Hard colloidal rods near a soft wall: wetting, drying, and symmetry breaking

Within an Onsager-like density functional theory we explore the thermodynamic and structural properties of an isotropic and nematic fluid of hard needle-like colloids in contact with a hard substrate coated with a soft short-ranged attractive or repulsive layer. As a function of the range and the strength of the soft interactions we find wetting and drying transitions, a pre-drying line, and a symmetry-breaking transition from uniaxial to biaxial in the wetting and drying film.Comment: 7 pages, 2 figure

Electroviscous effects of simple electrolytes under shear

On the basis of a hydrodynamical model analogous to that in critical fluids, we investigate the influences of shear flow upon the electrostatic contribution to the viscosity of binary electrolyte solutions in the Debye-H\"{u}ckel approximation. Within the linear-response theory, we reproduce the classical limiting law that the excess viscosity is proportional to the square root of the concentration of the electrolyte. We also extend this result for finite shear. An analytic expression of the anisotropic structure factor of the charge density under shear is obtained, and its deformation at large shear rates is discussed. A non-Newtonian effect caused by deformations of the ionic atmosphere is also elucidated for $\tau_D\dot{\gamma}>1$. This finding concludes that the maximum shear stress that the ionic atmosphere can support is proportional to $\lambda_D^{-3}$, where $\dot{\gamma}$, $\lambda_D$ and $\tau_D=\lambda_D^2/D$ are, respectively, the shear rate, the Debye screening length and the Debye relaxation time with $D$ being the relative diffusivity at the infinite dilution limit of the electrolyte.Comment: 13pages, 2figure

Anomalous magneto-oscillations and spin precession

A semiclassical analysis based on concepts developed in quantum chaos reveals that anomalous magneto-oscillations in quasi two-dimensional systems with spin-orbit interaction reflect the non-adiabatic spin precession of a classical spin vector along the cyclotron orbits.Comment: 4 pages, 2 figure

Fluctuation-dissipation theorem and quantum tunneling with dissipation at finite temperature

A reformulation of the fluctuation-dissipation theorem of Callen and Welton is presented in such a manner that the basic idea of Feynman-Vernon and Caldeira -Leggett of using an infinite number of oscillators to simulate the dissipative medium is realized manifestly without actually introducing oscillators. If one assumes the existence of a well defined dissipative coefficient $R(\omega)$ which little depends on the temperature in the energy region we are interested in, the spontanous and induced emissions as well as induced absorption of these effective oscillators with correct Bose distribution automatically appears. Combined with a dispersion relation, we reproduce the tunneling formula in the presence of dissipation at finite temperature without referring to an explicit model Lagrangian. The fluctuation-dissipation theorem of Callen-Welton is also generalized to the fermionic dissipation (or fluctuation) which allows a transparent physical interpretation in terms of second quantized fermionic oscillators. This fermionic version of fluctuation-dissipation theorem may become relevant in the analyses of, for example, fermion radiation from a black hole and also supersymmetry at the early universe.Comment: 19 pages. Phys. Rev. E (in press

Nematic-Isotropic Spinodal Decomposition Kinetics of Rod-like Viruses

We investigate spinodal decomposition kinetics of an initially nematic dispersion of rod-like viruses (fd virus). Quench experiments are performed from a flow-stabilized homogeneous nematic state at high shear rate into the two-phase isotropic-nematic coexistence region at zero shear rate. We present experimental evidence that spinodal decomposition is driven by orientational diffusion, in accordance with a very recent theory.Comment: 17 pages, 6 figures, accepted in Phys. Rev.

On the calculation of the self-diffusion coefficient of interacting Brownian particles

We consider two ways to calculate the self-diffusion coefficient of interacting Brownian particles. The first approach is based on the calculation of the mean square displacement of a Brownian particle starting from the Smoluchowski equation. In the second approach the self-diffusion coefficient is obtained as the product of the thermodynamic driving force and the mobility. The advantages and limitations of the two methods are discussed

Entanglement perturbation theory for the quantum ground states in two dimensions

A simple, general and practically exact method, Entanglement Perturbation Theory (EPT), is formulated to calculate the ground states of 2D macroscopic quantum systems with translational symmetry. An emphasis will be placed on the applicability of EPT to fermions. We will discuss some preliminary evidences which indicate a potential of EPT