663 research outputs found
Zonal flow generation and its feedback on turbulence production in drift wave turbulence
Plasma turbulence described by the Hasegawa-Wakatani equations has been
simulated numerically for different models and values of the adiabaticity
parameter C. It is found that for low values of C turbulence remains isotropic,
zonal flows are not generated and there is no suppression of the meridional
drift waves and of the particle transport. For high values of C, turbulence
evolves toward highly anisotropic states with a dominant contribution of the
zonal sector to the kinetic energy. This anisotropic flow leads to a decrease
of a turbulence production in the meridional sector and limits the particle
transport across the mean isopycnal surfaces. This behavior allows to consider
the Hasegawa-Wakatani equations a minimal PDE model which contains the
drift-wave/zonal-flow feedback loop prototypical of the LH transition in plasma
devices.Comment: 14 pages, 7 figure
Second generation diffusion model of interacting gravity waves on the surface of deep fluid
We propose a second generation phenomenological model for nonlinear interaction of gravity waves on the surface of deep water. This model takes into account the effects of non-locality of the original Hasselmann diffusion equation still preserving important properties of the first generation model: physically consistent scaling, adherence to conservation laws and the existence of Kolmogorov-Zakharov solutions. Numerical comparison of both models with the original Hasselmann equation shows that the second generation models improves the angular distribution in the evolving wave energy spectrum
Mesoscopic wave turbulence
We report results of sumulation of wave turbulence. Both inverse and direct
cascades are observed. The definition of "mesoscopic turbulence" is given. This
is a regime when the number of modes in a system involved in turbulence is high
enough to qualitatively simulate most of the processes but significantly
smaller then the threshold which gives us quantitative agreement with the
statistical description, such as kinetic equation. Such a regime takes place in
numerical simulation, in essentially finite systems, etc.Comment: 5 pages, 11 figure
The amplifier of unipolar pulses of the short range radar system
The amplifier of videopulses intended for work as a source of a pulse feed of the Hannah diodes 3А763А-M of the short range radar system is described. Characteristics of the amplifier are: coefficient of amplification 16 dB; the maximal amplitude of output pulses - 6 V; the maximal current in a pulse - 2,5 A
Research of high-current pulsed electron beam energy distribution in depth of sheet of water
Distribution of the absorbed doze and energy of the high-current pulsed electron beam formed by accelerator TEU-500 (350...500 kV, 60 ns, current density 0,3...0,4 kA/sm2) in water sheet depth has been measured. The high-resolution measurement technique of doze and energy distribution with application of dosimetric film based on lavsan with phenazine covering was used. Spatial resolution at registration of the absorbed doze in the range of 5...100 kGr amounts to 20...30 mkm. It was shown that at absorption of electron beam with high current density (in conditions of track overlapping on surface of the absorbing layer) distribution of the absorbed doze in thedepth within the limits of ±10 % coincides with distribution obtained for low-current bea
Second generation diffusion model of interacting gravity waves on the surface of deep fluid
International audienceWe propose a second generation phenomenological model for nonlinear interaction of gravity waves on the surface of deep water. This model takes into account the effects of non-locality of the original Hasselmann diffusion equation still preserving important properties of the first generation model: physically consistent scaling, adherence to conservation laws and the existence of Kolmogorov-Zakharov solutions. Numerical comparison of both models with the original Hasselmann equation shows that the second generation models improves the angular distribution in the evolving wave energy spectrum
Quantum quenches in fractonic field theories
We study out-of-equilibrium dynamics caused by global quantum quenches in
fractonic scalar field theories. We consider several types of quenches, in
particular, the mass quench in theories with different types of discrete
rotational symmetries ( and ), as well as an
instantaneous quench via the transition between them. We also investigate
fractonic boundary quenches, where the initial state is prepared on a
finite-width slab in Euclidean time. We find that perturbing a fractonic system
in finite volume especially highlights the restricted mobility via the
formation and subsequent evolution of specific -symmetric spatial
structures. We discuss a generalization to -symmetric field
theories, and introduce a proper regularization, which allows us to explicitly
deal with divergences inherent to fractonic field theories.Comment: v1: 21 pages, 8 figures; v2: 20 pages, 8 figures, minor correction
Joint statistics of amplitudes and phases in Wave Turbulence
Random Phase Approximation (RPA) provides a very convenient tool to study the
ensembles of weakly interacting waves, commonly called Wave Turbulence. In its
traditional formulation, RPA assumes that phases of interacting waves are
random quantities but it usually ignores randomness of their amplitudes.
Recently, RPA was generalised in a way that takes into account the amplitude
randomness and it was applied to study of the higher momenta and probability
densities of wave amplitudes. However, to have a meaningful description of wave
turbulence the RPA properties assumed for the initial fields must be proven to
survive over the nonlinear evolution time, and such a proof is the main goal of
the present paper. We derive an evolution equation for the full probability
density function which contains the complete information about the joint
statistics of all wave amplitudes and phases. We show that, for any initial
statistics of the amplitudes, the phase factors remain statistically
independent uniformly distributed variables. If in addition the initial
amplitudes are also independent variables (but with arbitrary distributions)
they will remain independent when considered in small sets which are much less
than the total number of modes. However, if the size of a set is of order of
the total number of modes then the joint probability density for this set is
not factorisable into the product of one-mode probabilities. In the other
words, the modes in such a set are involved in a ``collective'' (correlated)
motion. We also study new type of correlators describing the phase statistics.Comment: 27 pages, uses feynmf packag
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