3,757 research outputs found
The eddy heat-flux in rotating turbulent convection
The three components of the heat-flux vector F_\thetaF_r
which for \emph{free} turbulence is also believed to peak at the poles (see Eq.
(19) below). As we can show, however, the consequences of this unexpected
result (also obtained by Kaepylae, Korpi and Tuominen 2004) for the theory of
differential rotation are small as mainly the F_\thetaF_\phiF_\phi$ is closely related to the radial
\Lambda-effect which is known to be also negative in stratified and rapidly
rotating convection zones.Comment: 8 pages, 9 figures, Astron. Astrophys. (subm.
Covariant Treatment of Neutrino Spin (Flavour) Conversion in Matter under the Influence of Electromagnetic Fields
Within the recently proposed Lorentz invariant formalism for description of
neutrino spin evolution in presence of an arbitrary electromagnetic fields
effects of matter motion and polarization are considered.Comment: Extended version of contribution to "Particle Physics on Boundary of
Millenniums" (Proceedings of the 9th Lomonosov Conference on Elementary
Particle Physics, World Scientific, Singapure
Dark matter implications of the WMAP-Planck Haze
Gamma rays and microwave observations of the Galactic Center and surrounding
areas indicate the presence of anomalous emission, whose origin remains
ambiguous. The possibility of dark matter (DM) annihilation explaining both
signals through prompt emission at gamma-rays and secondary emission at
microwave frequencies from interactions of high-energy electrons produced in
annihilation with the Galactic magnetic fields has attracted much interest in
recent years. We investigate the DM interpretation of the Galactic Center
gamma-ray excess by searching for the associated synchrotron in the WMAP-Planck
data. Considering various magnetic field and cosmic-ray propagation models, we
predict the synchrotron emission due to DM annihilation in our Galaxy, and
compare it with the WMAP-Planck data at 23-70GHz. In addition to standard
microwave foregrounds, we separately model the microwave counterpart to the
Fermi Bubbles and the signal due to DM, and use component separation techniques
to extract the signal associated with each template from the total emission. We
confirm the presence of the Haze at the level of 7% of the total sky intensity
at 23GHz in our chosen region of interest, with a harder spectrum than the synchrotron from regular cosmic-ray electrons. The data do
not show a strong preference towards fitting the Haze by either the Bubbles or
DM emission only. Inclusion of both components provides a better fit with a DM
contribution to the Haze emission of 20% at 23GHz, however, due to significant
uncertainties in foreground modeling, we do not consider this a clear detection
of a DM signal. We set robust upper limits on the annihilation cross section by
ignoring foregrounds, and also report best-fit DM annihilation parameters
obtained from a complete template analysis. We conclude that the WMAP-Planck
data are consistent with a DM interpretation of the gamma-ray excess.Comment: 34 pages, 9 figure
Low – frequency acoustic instability of the working process in the combustion chamber of the solid propellant rocket engine
The following problems is investigated by statement of direct numerical experiment in offered paper. 1) The real oscillatory process is reproduced. 2) The mechanism of occurrence and refill of low-frequency acoustic instability in the combustion chamber of the solid propellant rocket.. The direct numerical modeling of low-frequency acoustic instability will be carried out by a Davydov’s method. This powerful numerical method was discovered by Yuri M. Davydov 40 years ago as the method of large particles The further modern complex improvement of this numerical technique was titled Davydov’s method. It is good itself recommending at the decision of many tasks of the mechanics of continuous media. The description of physical and mathematical model of flow in the rocket engine combustion chamber is given. The results of numerical modeling are resulted. The hydrodynamical deeply nonlinear nature of low-frequency fluctuations connected to structure and character of current in the combustion chamber of the solid propellant rocket engine proves to be tru
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