399 research outputs found
An analytic solution of the Boltzmann equation in the presence of self-generated magnetic fields in astrophysical plasmas
Through relating a self-generated magnetic field to the regular motion of
free electrons that is responsible for the magnetic field generation in
astrophysical plasmas, we solve the Boltzmann kinetic equation in the presence
of the self-generated magnetic fields to obtain a steady-state, collisional
invariant analytic solution of the equation.Comment: 4 pages, no figure, in REVTeX, accepted for publication in Phys.
lett.
Differential Form of the Collision Integral for a Relativistic Plasma
The differential formulation of the Landau-Fokker-Planck collision integral
is developed for the case of relativistic electromagnetic interactions.Comment: Plain TeX, 5 page
A quantum kinetic equation for Fermi-systems including three-body correlations
A single-time quantum transport equation, which includes effects beyond the
quasiparticle approximation, is derived for Fermi-systems in the framework of
non-equilibrium real-time Green's functions theory. Ternary correlations are
incorporated in the kinetic description via a cluster expansion for the
self-energies (e.g., the transport vertex and the width) truncated at the level
of three-body scattering amplitudes. A finite temperature/density formulation
of the three-body problem is given. Corresponding three-body equations reduce
to the well-known Faddeev equations in the vacuum limit. In equilibrium the
equation of state contains virial corrections proportional to the third quantum
virial coefficient.Comment: 25 pages, Revtex, 2 figures. Final version to be published in Annals
of Physics (NY), with minor change
The Rayleigh-Taylor instability and internal waves in quantum plasmas
Influence of quantum effects on the internal waves and the Rayleigh-Taylor
instability in plasma is investigated. It is shown that quantum pressure always
stabilizes the RT instability. The problem is solved both in the limit of
short-wavelength perturbations and exactly for density profiles with layers of
exponential stratification. In the case of stable stratification, quantum
pressure modifies the dispersion relation of the inertial waves. Because of the
quantum effects, the internal waves may propagate in the transverse direction,
which was impossible in the classical case. A specific form of pure quantum
internal waves is obtained, which do not require any external gravitational
field.Comment: 9 pages, 2 figure
Kinetic Theory of Radiation in Nonequilibrium Relativistic Plasmas
Many-particle QED is applied to kinetic theory of radiative processes in
many- component plasmas with relativistic electrons and nonrelativistic heavy
particles. Within the framework of nonequilibrium Green's function technique,
transport and mass-shell equations for fluctuations of the electromagnetic
field are obtained. We show that the transverse field correlation functions can
be decomposed into sharply peaked (non-Lorentzian) parts that describe resonant
(propagating) photons and off-shell parts corresponding to virtual photons in
plasmas. Analogous decomposi- tions are found for the longitudinal field
correlation functions and the correlation functions of relativistic electrons.
As a novel result a kinetic equation for the reso- nant photons with a finite
spectral width is derived. The off-shell parts of the particle and field
correlation functions are shown to be essential to calculate the local ra-
diating power in relativistic plasmas and recover the results of vacuum QED.
The influence of plasma effects and collisional broadening of the relativistic
quasiparticle spectral function on radiative processes is discussed.Comment: 63 pages, 11 figure
Transport Theory of Massless Fields
Using the Schwinger-Keldysh technique we discuss how to derive the transport
equations for the system of massless quantum fields. We analyse the scalar
field models with quartic and cubic interaction terms. In the model
the massive quasiparticles appear due to the self-interaction of massless bare
fields. Therefore, the derivation of the transport equations strongly resembles
that one of the massive fields, but the subset of diagrams which provide the
quasiparticle mass has to be resummed. The kinetic equation for the finite
width quasiparticles is found, where, except the mean-field and collision
terms, there are terms which are absent in the standard Boltzmann equation. The
structure of these terms is discussed. In the massless model the
massive quasiparticles do not emerge and presumably there is no transport
theory corresponding to this model. It is not surprising since the
model is anyhow ill defined.Comment: 32 pages, no macro
In-medium relativistic kinetic theory and nucleon-meson systems
Within the model of coupled nucleon-meson systems, a
generalized relativistic Lenard--Balescu--equation is presented resulting from
a relativistic random phase approximation (RRPA). This provides a systematic
derivation of relativistic transport equations in the frame of nonequilibrium
Green's function technique including medium effects as well as flucuation
effects. It contains all possible processes due to one meson exchange and
special attention is kept to the off--shell character of the particles. As a
new feature of many particle effects, processes are possible which can be
interpreted as particle creation and annihilation due to in-medium one meson
exchange. In-medium cross sections are obtained from the generalized derivation
of collision integrals, which possess complete crossing symmetries.Comment: See nucl-th/9310032 for revised version which the authors
incompetently resubmitted rather than correctly replacing thi
Nonequilibrium Quantum-Field Dynamics and Off-Shell Transport for -theory in 2+1 dimensions
We solve the Kadanoff-Baym equations for nonequilibrium initial
configurations of the -theory in 2+1 dimensions and compare to explicit
solutions of generalized transport equations for the same theory. The latter
transport equations are derived from the Kadanoff-Baym equation in a first
order gradient expansion in phase space and explicitly retain the off-shell
dynamics as inherent in the time-dependent spectral functions. The solutions of
these equations compare very well with the exact solutions of the full
Kadanoff-Baym equations with respect to the occupation numbers of the
individual modes, the spectral evolution as well as the chemical equilibration
process. Furthermore, the proper equilibrium off-shell distribution is reached
for large times contrary to the quasiparticle Boltzmann limit. We additionally
present a direct comparison of the solution of the generalized transport
equations in the Kadanoff-Baym and Botermans-Malfliet form; both solutions are
found to agree very well with each other.Comment: 43 pages, LaTex, including 15 postscript figures, submitted to Nucl.
Phys.
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