222 research outputs found
Transport Far From Equilibrium --- Uniform Shear Flow
The BGK model kinetic equation is applied to spatially inhomogeneous states
near steady uniform shear flow. The shear rate of the reference steady state
can be large so the states considered include those very far from equilibrium.
The single particle distribution function is calculated exactly to first order
in the deviations of the hydrodynamic field gradients from their values in the
reference state. The corresponding non-linear hydrodynamic equaitons are
obtained and the set of transport coefficients are identified as explicit
functions of the shear rate. The spectrum of the linear hydrodynamic equation
is studied in detail and qualitative differences from the spectrum for
equilibrium fluctuations are discussed. Conditions for instabilities at long
wavelengths are identified and disccused.Comment: 32 pages, 1 figure, RevTeX, submitted to Phys. Rev.
Kinetic Theory for Electron Dynamics Near a Positive Ion
A theoretical description of time correlation functions for electron
properties in the presence of a positive ion of charge number Z is given. The
simplest case of an electron gas distorted by a single ion is considered. A
semi-classical representation with a regularized electron - ion potential is
used to obtain a linear kinetic theory that is asymptotically exact at short
times. This Markovian approximation includes all initial (equilibrium) electron
- electron and electron - ion correlations through renormalized pair
potentials. The kinetic theory is solved in terms of single particle
trajectories of the electron - ion potential and a dielectric function for the
inhomogeneous electron gas. The results are illustrated by a calculation of the
autocorrelation function for the electron field at the ion. The dependence on
charge number Z is shown to be dominated by the bound states of the effective
electron - ion potential. On this basis, a very simple practical representation
of the trajectories is proposed and shown to be accurate over a wide range
including strong electron - ion coupling. This simple representation is then
used for a brief analysis of the dielectric function for the inhomogeneous
electron gas.Comment: 30 pages, 5 figures, submitted to Journal of Statistical Mechanics:
Theory and Experimen
Nonlinear response of electrons to a positive ion
Electric field dynamics at a positive ion imbedded in an electron gas is
considered using a semiclassical description. The dependence of the field
autocorrelation function on charge number is studied for strong ion-electron
coupling via MD simulation. The qualitative features for larger charge numbers
are a decreasing correlation time followed by an increasing anticorrelation.
Stopping power and related transport coefficients determined by the time
integral of this correlation function result from the competing effects of
increasing initial correlations and decreasing dynamical correlations. An
interpretation of the MD results is obtained from an effective single particle
model showing good agreement with the simulation results.Comment: To be published in the proceedings of the International Workshop on
Strongly Coupled Coulomb Systems, Journal of Physics
- …