5,608 research outputs found
Anomalous Diffusion in Velocity Space
The problem of anomalous diffusion in the momentum space is considered on the
basis of the appropriate probability transition function (PTF). New general
equation for description of the diffusion of heavy particles in the gas of the
light particles is formulated on basis of the new approach similar to one in
coordinate space (S. Trigger et al.). The obtained results permit to describe
the various situations when the probability transition function (PTF) has a
long tail in the momentum space. The effective friction and diffusion
coefficients are found.Comment: 11 pages, no figures and table
Constraining CP-Violating TGCs and Measuring W-Polarization at OPAL
A measurement of the polarization of W bosons in semi-leptonically decaying W
pairs produced at 189 GeV is presented. Rates of longitudinally and
transversely polarized W bosons and correlation between two W bosons are
studied. The spin properties of the leptonically decaying W boson in the W
pairs was used to measure the CP-violating trilinear gauge boson couplings.
These results are compared with Standard Model expectations.Comment: Proceedings of the XXXth International Symposium on Multiparticle
Dynamics (ISMD2000), 9-15 October 2000, Tihany, Hungary. 6 pages, 2 figures
(LaTex, encapsulated PostScript
Velocity-Dependent Friction and Diffusion for Grains in Neutral Gases, Dusty Plasmas and Active Systems
A self-consistent and universal description of friction and diffusion for
Brownian particles (grains) in different systems, as a gas with Boltzmann
collisions, dusty plasma with ion absorption by grains, and for active
particles (e.g., cells in biological systems) is suggested on the basis of the
appropriate Fokker-Planck equation. Restrictions for application of the
Fokker-Planck equation to the problem of velocity-dependent friction and
diffusion coefficients are found. General description for this coefficient is
formulated on the basis of master equation. Relation of the diffusion
coefficient in the coordinate and velocity spaces is found for active (capable
to transfer momentum to the ambient media) and passive particles in the
framework of the Fokker-Planck equation.
The problem of anomalous space diffusion is formulated on the basis of the
appropriate probability transition (PT) function. The method of partial
differentiation is avoided to construct the correct probability distributions
for arbitrary distances, what is important for applications to different
stochastic problems. Generale equation for time-dependent PT function is
formulated and discussed.
Generalized friction in the velocity space is determined and applied to
describe the friction force itself as well as the drag force in the case of a
non-zero driven ion velocity in plasmas. The negative friction due to ion
scattering on grains exists and can be realized for the appropriate
experimental conditions.Comment: 21 page
Anomalous Transport in Velocity Space, from Fokker-Planck to General Equation
The problem of anomalous diffusion in momentum (velocity) space is considered
based on the master equation and the appropriate probability transition
function (PTF). The approach recently developed by the author for coordinate
space, is applied with necessary modifications to velocity space. A new general
equation for the time evolution of the momentum distribution function in
momentum space is derived. This allows the solution of various problems of
anomalous transport when the probability transition function (PTF) has a long
tail in momentum space. For the opposite cases of the PTF rapidly decreasing as
a function of transfer momenta (when large transfer momenta are strongly
suppressed), the developed approach allows us to consider strongly
non-equilibrium cases of the system evolution. The stationary and
non-stationary solutions are studied. As an example, the particular case of the
Boltzmann-type PT-function for collisions of heavy and light particles with the
determined (prescribed) distribution function, which can be strongly
non-equilibrium, is considered within the proposed general approach. The
appropriate diffusion and friction coefficients are found. The Einstein
relation between the friction and diffusion coefficients is shown to be
violated in these cases.Comment: 23 pages, 0 figure
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