3,021 research outputs found
Burgers turbulence with pressure
The randomly driven Burgers equation with pressure is considered as a 1D
model of strong turbulence of compressible fluid. It is shown that infinitely
small pressure provides a finite effect on the velocity and density statistics
and this case therefore is qualitatively different from turbulence without
pressure. We establish the corresponding operator product expansion and predict
the intermittent velocity- difference and mass-difference PDFs. We then apply
the developed methods to the statistics of a passive scalar advected by the
Burgers field.Comment: 4 pages, revte
Ferromagnetic Detectors of Axions in RF (S - X) Band
The (pseudo) Goldstone bosons arise naturally in many modern theories such as
supergravity, superstring theory and variants of general relativity with
torsion. By the other hand, there are well known indications that a large part
of the Universe mass exists in a form of dark matter. The most attractive model
of the dark matter is non-relativistic gas of the light elementary particles
weakly interacting with the "usual" matter \cite{b2} - \cite{b4}. We describe
ferromagnetic detectors, for search of arion(axion), where a high-sensitive
two-channel SHF receiver is used. Its sensitivity reaches to ,
with time of accumulation . Fourier analysis of signal provides a
survey in zone up to with spectral resolution .
There was applied a high sensitive SHF receiver based on a special computer
method of coherent accumulation of signals. It is possible to use the receiver
in other precise experiments: measuring of electron/positron beams polarization
in storage rings, investigation of parity violation, investigation of
atmosphere with radars etc.Comment: 6 pages, LaTeX, no figure
Structure Function Scaling of a 2MASS Extinction Map of Taurus
We compute the structure function scaling of a 2MASS extinction map of the
Taurus molecular cloud complex. The scaling exponents of the structure
functions of the extinction map follow the Boldyrev's velocity structure
function scaling of supersonic turbulence. This confirms our previous result
based on a spectral map of 13CO J=1-0 covering the same region and suggests
that supersonic turbulence is important in the fragmentation of this
star--forming cloud.Comment: submitted to Ap
Shell to shell energy transfer in MHD, Part I: steady state turbulence
We investigate the transfer of energy from large scales to small scales in
fully developed forced three-dimensional MHD-turbulence by analyzing the
results of direct numerical simulations in the absence of an externally imposed
uniform magnetic field. Our results show that the transfer of kinetic energy
from the large scales to kinetic energy at smaller scales, and the transfer of
magnetic energy from the large scales to magnetic energy at smaller scales, are
local, as is also found in the case of neutral fluids, and in a way that is
compatible with Kolmogorov (1941) theory of turbulence. However, the transfer
of energy from the velocity field to the magnetic field is a highly non-local
process in Fourier space. Energy from the velocity field at large scales can be
transfered directly into small scale magnetic fields without the participation
of intermediate scales. Some implications of our results to MHD turbulence
modeling are also discussed.Comment: Submitted to PR
A note on Burgers' turbulence
In this note the Polyakov equation [Phys. Rev. E {\bf 52} (1995) 6183] for
the velocity-difference PDF, with the exciting force correlation function
is analyzed. Several solvable cases are
considered, which are in a good agreement with available numerical results.
Then it is shown how the method developed by A. Polyakov can be applied to
turbulence with short-scale-correlated forces, a situation considered in models
of self-organized criticality.Comment: 11 pages, Late
Bifurcations observed in the spectra of coupled electron-phonon modes in multiferroic subjected to a magnetic field
We report on bifurcations effect mediated by the electron-phonon coupling in
a concentrated rare-earth-containing antiferromagnet, observed in the spectra
of coupled -electron-phonon modes under the influence of an external
magnetic field. The effect was observed in the low-temperature far-infrared
(terahertz) reflection spectra of a multiferroic easy-axis antiferromagnet
in magnetic fields . Both paramagnetic
and magnetically ordered phases (including a spin-flop one) were studied in
magnetic fields up to 30 T. We show that the field behavior of the coupled
modes can be successfully explained and modeled on the base of the equation
derived in the frame of the theory of coupled electron-phonon modes, with the
same field-independent electron-phonon interaction constant .Comment: 5 pages, 4 figure
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