14,619 research outputs found
Spinodal decomposition: An alternate mechanism of phase conversion
The scenario of homogeneous nucleation is investigated for a first order
quark-hadron phase transition in a rapidly expanding background of quark gluon
plasma. It is found that significant supercooling is possible before
hadronization begins. This study also suggests that spinodal decomposition
competes with nucleation and may provide an alternative mechanism for phase
conversion.Comment: LaTeX, 4 pages with 3 Postscript figures. Talk given at International
Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2001),
Nov. 26-30, 2001, Jaipur, Indi
Linear and nonlinear properties of Rao-dust-Alfv\'en waves in magnetized plasmas
The linear and nonlinear properties of the Rao-dust-magnetohydrodynamic
(R-D-MHD) waves in a dusty magnetoplasma are studied. By employing the
inertialess electron equation of motion, inertial ion equation of motion,
Amp\`ere's law, Faraday's law, and the continuity equation in a plasma with
immobile charged dust grains, the linear and nonlinear propagation of
two-dimensional R-D-MHD waves are investigated. In the linear regime, the
existence of immobile dust grains produces the Rao cutoff frequency, which is
proportional to the dust charge density and the ion gyrofrequency. On the other
hand, the dynamics of an amplitude modulated R-D-MHD waves is governed by the
cubic nonlinear Schroedinger equation. The latter has been derived by using the
reductive perturbation technique and the two-timescale analysis which accounts
for the harmonic generation nonlinearity in plasmas. The stability of the
modulated wave envelope against non-resonant perturbations is studied. Finally,
the possibility of localized envelope excitations is discussed.Comment: 30 pages, 8 figures, to appear in Physics of Plasma
Nonlinear wave-wave interactions in quantum plasmas
Wave-wave interaction in plasmas is a topic of important research since the
16th century. The formation of Langmuir solitons through the coupling of
high-frequency (hf) Langmuir and low-frequency (lf) ion-acoustic waves, is one
of the most interesting features in the context of turbulence in modern plasma
physics. Moreover, quantum plasmas, which are ubiquitous in ultrasmall
electronic devices, micromechanical systems as well as in dense astrophysical
environments are a topic of current research. In the light of notable interests
in such quantum plasmas, we present here a theoretical investigation on the
nonlinear interaction of quantum Langmuir waves (QLWs) and quantum ion-acoustic
waves (QIAWs), which are governed by the one-dimensional quantum Zakharov
equations (QZEs). It is shown that a transition to spatiotemporal chaos (STC)
occurs when the length scale of excitation of linear modes is larger than that
of the most unstable ones. Such length scale is, however, to be larger
(compared to the classical one) in presence of the quantum tunneling effect.
The latter induces strong QIAW emission leading to the occurrence of collision
and fusion among the patterns at an earlier time than the classical case.
Moreover, numerical simulation of the QZEs reveals that many solitary patterns
can be excited and saturated through the modulational instability (MI) of
unstable harmonic modes. In a longer time, these solitons are seen to appear in
the state of STC due to strong QIAW emission as well as by the collision and
fusion in stochastic motion. The energy in the system is thus strongly
redistributed, which may switch on the onset of Langmuir turbulence in quantum
plasmas.Comment: 6 pages, 6 figures (To appear in AIP Conf. Proceedings 2010
Nonlinear theory of solitary waves associated with longitudinal particle motion in lattices - Application to longitudinal grain oscillations in a dust crystal
The nonlinear aspects of longitudinal motion of interacting point masses in a
lattice are revisited, with emphasis on the paradigm of charged dust grains in
a dusty plasma (DP) crystal. Different types of localized excitations,
predicted by nonlinear wave theories, are reviewed and conditions for their
occurrence (and characteristics) in DP crystals are discussed. Making use of a
general formulation, allowing for an arbitrary (e.g. the Debye electrostatic or
else) analytic potential form and arbitrarily long site-to-site range
of interactions, it is shown that dust-crystals support nonlinear kink-shaped
localized excitations propagating at velocities above the characteristic DP
lattice sound speed . Both compressive and rarefactive kink-type
excitations are predicted, depending on the physical parameter values, which
represent pulse- (shock-)like coherent structures for the dust grain relative
displacement. Furthermore, the existence of breather-type localized
oscillations, envelope-modulated wavepackets and shocks is established. The
relation to previous results on atomic chains as well as to experimental
results on strongly-coupled dust layers in gas discharge plasmas is discussed.Comment: 21 pages, 12 figures, to appear in Eur. Phys. J.
- …