9,803 research outputs found
Theory of stability of large amplitude periodic /BGK/ waves in collisionless plasmas
Stability theory of large amplitude periodic BGK waves in collisionless plasmas using distribution function
Origin of spontaneous violation of the Lorentz symmetry: Vortices in the cosmos
By carefully studying the (1,0)+(0,1) representation space for massive
particles we point to the existence of certain inherent tachyonic dispersion
relations: E^2= p^2-m^2. We put forward an interpretation that exploits these
``negative mass squared'' solutions; rotational invariance is spontaneously
broken. Relevance of these results to the vortices in the cosmos is pointed
out.
NOTE: Just as "negative energy solutions'' of Dirac equation are
re-interpreted as antiparticles, similarly the possibility exists for
re-interpreting the tachyonic dispersion relations of all (j,0)+(0,j)
representation spaces via spontaneous Lorentz symmetry breaking. In Mod. Phys.
Lett. A8:2623-2630,1993 we exhibited this explicitly for the j=1 representation
space. The interest in this old subject has grown markedly in recent years as
is evident from numerous theoretical and phenomenological works on the subject.
With this observation, we make this replacement of our paper fourteen years
after its initial publication. The Abstract and main text remain unaltered. The
title is changed to reflect the underlying physics more closely.Comment: This is an exact copy of the published paper with an extended
bibliography and a revised title. A brief note is added to point out a
systematic way to spontaneously break Lorentz symmetr
Buneman instability in a magnetized current-carrying plasma with velocity shear
Buneman instability is often driven in magnetic reconnection. Understanding
how velocity shear in the beams driving the Buneman instability affects the
growth and saturation of waves is relevant to turbulence, heating, and
diffusion in magnetic reconnection. Using a Mathieu-equation analysis for weak
cosine velocity shear together with Vlasov simulations, the effects of shear on
the kinetic Buneman instability are studied in a plasma consisting of strongly
magnetized electrons and cold unmagnetized ions. In the linearly unstable
phase, shear enhances the coupling between oblique waves and the sheared
electron beam, resulting in a wider range of unstable eigenmodes with common
lower growth rates. The wave couplings generate new features of the electric
fields in space, which can persist into the nonlinear phase when electron holes
form. Lower hybrid instabilities simultaneously occur at
with a much lower growth
rate, and are not affected by the velocity shear.Comment: Accepted by Physics of Plasm
Electron interferometry in quantum Hall regime: Aharonov-Bohm effect of interacting electrons
An apparent h/fe Aharonov-Bohm flux period, where f is an integer, has been
reported in coherent quantum Hall devices. Such sub-period is not expected for
non-interacting electrons and thus is thought to result from interelectron
Coulomb interaction. Here we report experiments in a Fabry-Perot interferometer
comprised of two wide constrictions enclosing an electron island. By carefully
tuning the constriction front gates, we find a regime where interference
oscillations with period h/2e persist throughout the transition between the
integer quantum Hall plateaus 2 and 3, including half-filling. In a large
quantum Hall sample, a transition between integer plateaus occurs near
half-filling, where the bulk of the sample becomes delocalized and thus
dissipative bulk current flows between the counterpropagating edges
("backscattering"). In a quantum Hall constriction, where conductance is due to
electron tunneling, a transition between forward- and back-scattering is
expected near the half-filling. In our experiment, neither period nor amplitude
of the oscillations show a discontinuity at half-filling, indicating that only
one interference path exists throughout the transition. We also present
experiments and an analysis of the front-gate dependence of the phase of the
oscillations. The results point to a single physical mechanism of the observed
conductance oscillations: Aharonov-Bohm interference of interacting electrons
in quantum Hall regime.Comment: 10 pages, 4 Fig
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