493 research outputs found
Stable Equilibrium Based on L\'evy Statistics: Stochastic Collision Models Approach
We investigate equilibrium properties of two very different stochastic
collision models: (i) the Rayleigh particle and (ii) the driven Maxwell gas.
For both models the equilibrium velocity distribution is a L\'evy distribution,
the Maxwell distribution being a special case. We show how these models are
related to fractional kinetic equations. Our work demonstrates that a stable
power-law equilibrium, which is independent of details of the underlying
models, is a natural generalization of Maxwell's velocity distribution.Comment: PRE Rapid Communication (in press
Multi-parameter generalization of nonextensive statistical mechanics
We show that the stochastic interpretation of Tsallis' thermostatistics given
recently by Beck [Phys. Rev. Lett {\bf 87}, 180601 (2001)] leads naturally to a
multi-parameter generalization. The resulting class of distributions is able to
fit experimental results which cannot be reproduced within the Boltzmann's or
Tsallis' formalism.Comment: ReVTex 4.0, 4 eps figure
Restriction of Helmholtz Model
The results of the experimental studies of physical mechanisms of energy dissipation in the oscillating
system in which air cavity held by the forces of magnetic levitation is used as the elastic element, and
magnetic fluid prepared on the basis of dispersing media with different viscosity level is used as the iner-tial element are considered in the article. Based on the obtained results the conclusion on the restriction of
the applicability of Helmholtz equation, caused by boundary effects is made.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3640
On the effective velocity created by a point vortex in two-dimensional hydrodynamics
We complete previous investigations on the statistics of velocity
fluctuations arising from a random distribution of point vortices in
two-dimensional hydrodynamics. We show that, on a statistical sense, the
velocity created by a point vortex is shielded by cooperative effects on a
distance , the inter-vortex separation. For , the ``effective'' velocity decays as instead of the ordinary
law recovered for . These results are similar to those
obtained by Agekyan [Sov. Astron. 5 (1962) 809] in his investigations on the
fluctuations of the gravitational field. They give further support to our
previous observation that the statistics of velocity fluctuations are
(marginally) dominated by the contribution of the nearest neighbor.Comment: Submitted to Phys. Rev.
Physics of Hermetic Sealing of Large Portion of Gas Using Magnetic Fluid Membrane
The physical mechanism of hermetic sealing and storing the air cavity of large volume, based on using
magnetic fluid membrane is considered in the article. The described method can be used to create devices
for sampling and further chemical analysis of gas in mines and at chemical industry enterprises.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3640
Kinetic theory of point vortices: diffusion coefficient and systematic drift
We develop a kinetic theory for point vortices in two-dimensional
hydrodynamics. Using standard projection operator technics, we derive a
Fokker-Planck equation describing the relaxation of a ``test'' vortex in a bath
of ``field'' vortices at statistical equilibrium. The relaxation is due to the
combined effect of a diffusion and a drift. The drift is shown to be
responsible for the organization of point vortices at negative temperatures. A
description that goes beyond the thermal bath approximation is attempted. A new
kinetic equation is obtained which respects all conservation laws of the point
vortex system and satisfies a H-theorem. Close to equilibrium this equation
reduces to the ordinary Fokker-Planck equation.Comment: 50 pages. To appear in Phys. Rev.
Onset of magnetism in B2 transition metals aluminides
Ab initio calculation results for the electronic structure of disordered bcc
Fe(x)Al(1-x) (0.4<x<0.75), Co(x)Al(1-x) and Ni(x)Al(1-x) (x=0.4; 0.5; 0.6)
alloys near the 1:1 stoichiometry, as well as of the ordered B2 (FeAl, CoAl,
NiAl) phases with point defects are presented. The calculations were performed
using the coherent potential approximation within the Korringa-Kohn-Rostoker
method (KKR-CPA) for the disordered case and the tight-binding linear
muffin-tin orbital (TB-LMTO) method for the intermetallic compounds. We studied
in particular the onset of magnetism in Fe-Al and Co-Al systems as a function
of the defect structure. We found the appearance of large local magnetic
moments associated with the transition metal (TM) antisite defect in FeAl and
CoAl compounds, in agreement with the experimental findings. Moreover, we found
that any vacancies on both sublattices enhance the magnetic moments via
reducing the charge transfer to a TM atom. Disordered Fe-Al alloys are
ferromagnetically ordered for the whole range of composition studied, whereas
Co-Al becomes magnetic only for Co concentration >0.5.Comment: 11 pages with 9 embedded postscript figures, to be published in
Phys.Rev.
Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton
Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using
data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000.
The corresponding integrated luminosity is 650 pb^{-1}. The values of the
cross-section obtained are found to be in agreement with QED predictions.
Limits on the anomalous magnetic and electric dipole moments of the tau lepton
are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.
Evidence for an Excess of Soft Photons in Hadronic Decays of Z^0
Soft photons inside hadronic jets converted in front of the DELPHI main
tracker (TPC) in events of qqbar disintegrations of the Z^0 were studied in the
kinematic range 0.2 < E_gamma < 1 GeV and transverse momentum with respect to
the closest jet direction p_T < 80 MeV/c. A clear excess of photons in the
experimental data as compared to the Monte Carlo predictions is observed. This
excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/-
0.27) x 10^{-3} gamma/jet in the specified kinematic region, while the expected
level of the inner hadronic bremsstrahlung (which is not included in the Monte
Carlo) is (0.340 +/- 0.001 +/- 0.038) x 10^{-3} gamma/jet. The ratio of the
excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8),
which is similar in strength to the anomalous soft photon signal observed in
fixed target experiments with hadronic beams.Comment: 37 pages, 9 figures, Accepted by Eur. Phys. J.
Study of Inclusive J/psi Production in Two-Photon Collisions at LEP II with the DELPHI Detector
Inclusive J/psi production in photon-photon collisions has been observed at
LEP II beam energies. A clear signal from the reaction gamma gamma -> J/psi+X
is seen. The number of observed N(J/psi -> mu+mu-) events is 36 +/- 7 for an
integrated luminosity of 617 pb^{-1}, yielding a cross-section of
sigma(J/psi+X) = 45 +/- 9 (stat) +/- 17 (syst) pb. Based on a study of the
event shapes of different types of gamma gamma processes in the PYTHIA program,
we conclude that (74 +/- 22)% of the observed J/psi events are due to
`resolved' photons, the dominant contribution of which is most probably due to
the gluon content of the photon.Comment: 13 pages, 8 figures, Accepted by Phys. Lett.
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