10,627 research outputs found
Dynamics of Solitons and Quasisolitons of Cubic Third-Order Nonlinear Schr\"odinger Equation
The dynamics of soliton and quasisoliton solutions of cubic third order
nonlinear Schr\"{o}dinger equation is studied. The regular solitons exist due
to a balance between the nonlinear terms and (linear) third order dispersion;
they are not important at small ( is the coefficient in
the third derivative term) and vanish at . The most essential,
at small , is a quasisoliton emitting resonant radiation (resonantly
radiating soliton). Its relationship with the other (steady) quasisoliton,
called embedded soliton, is studied analytically and in numerical experiments.
It is demonstrated that the resonantly radiating solitons emerge in the course
of nonlinear evolution, which shows their physical significance
Anomalous diffusion, clustering, and pinch of impurities in plasma edge turbulence
The turbulent transport of impurity particles in plasma edge turbulence is
investigated. The impurities are modeled as a passive fluid advected by the
electric and polarization drifts, while the ambient plasma turbulence is
modeled using the two-dimensional Hasegawa--Wakatani paradigm for resistive
drift-wave turbulence. The features of the turbulent transport of impurities
are investigated by numerical simulations using a novel code that applies
semi-Lagrangian pseudospectral schemes. The diffusive character of the
turbulent transport of ideal impurities is demonstrated by relative-diffusion
analysis of the evolution of impurity puffs. Additional effects appear for
inertial impurities as a consequence of compressibility. First, the density of
inertial impurities is found to correlate with the vorticity of the electric
drift velocity, that is, impurities cluster in vortices of a precise
orientation determined by the charge of the impurity particles. Second, a
radial pinch scaling linearly with the mass--charge ratio of the impurities is
discovered. Theoretical explanation for these observations is obtained by
analysis of the model equations.Comment: This article has been submitted to Physics of Plasmas. After it is
published, it will be found at http://pop.aip.org/pop
Bounds on Heavy-to-Heavy Mesonic Form Factors
We provide upper and lower bounds on the form factors for B -> D, D^* by
utilizing inclusive heavy quark effective theory sum rules. These bounds are
calculated to leading order in Lambda_QCD/m_Q and alpha_s. The O(alpha_s^2
beta_0) corrections to the bounds at zero recoil are also presented. We compare
our bounds with some of the form factor models used in the literature. All the
models we investigated failed to fall within the bounds for the combination of
form factors (omega^2 - 1)/(4 omega)|omega h_{A2}+h_{A3}|^2.Comment: 27 pages, 10 figure
Solitary wave interaction in a compact equation for deep-water gravity waves
In this study we compute numerical traveling wave solutions to a compact
version of the Zakharov equation for unidirectional deep-water waves recently
derived by Dyachenko & Zakharov (2011) Furthermore, by means of an accurate
Fourier-type spectral scheme we find that solitary waves appear to collide
elastically, suggesting the integrability of the Zakharov equation.Comment: 8 pages, 5 figures, 23 references. Other author's papers can be
downloaded at http://www.lama.univ-savoie.fr/~dutykh/ . arXiv admin note:
text overlap with arXiv:1204.288
Laser beam filamentation in fractal aggregates
We investigate filamentation of a cw laser beam in soft matter such as
colloidal suspensions and fractal gels. The process, driven by
electrostriction, is strongly affected by material properties, which are taken
into account via the static structure factor, and have impact on the statistics
of the light filaments.Comment: 4 pages, 5 figures. Revised version with corrected figure 5. To be
published in Phys. Rev. Let
The low dimensional dynamical system approach in General Relativity: an example
In this paper we explore one of the most important features of the Galerkin
method, which is to achieve high accuracy with a relatively modest
computational effort, in the dynamics of Robinson-Trautman spacetimes.Comment: 7 pages, 5 figure
Strong Collapse Turbulence in Quintic Nonlinear Schr\"odinger Equation
We consider the quintic one dimensional nonlinear Schr\"odinger equation with
forcing and both linear and nonlinear dissipation. Quintic nonlinearity results
in multiple collapse events randomly distributed in space and time forming
forced turbulence. Without dissipation each of these collapses produces finite
time singularity but dissipative terms prevents actual formation of
singularity. In statistical steady state of the developed turbulence the
spatial correlation function has a universal form with the correlation length
determined by the modulational instability scale. The amplitude fluctuations at
that scale are nearly-Gaussian while the large amplitude tail of probability
density function (PDF) is strongly non-Gaussian with power-like behavior. The
small amplitude nearly-Gaussian fluctuations seed formation of large collapse
events. The universal spatio-temporal form of these events together with the
PDF for their maximum amplitudes define the power-like tail of PDF for large
amplitude fluctuations, i.e., the intermittency of strong turbulence.Comment: 14 pages, 17 figure
What Thermodynamics tells about QCD Plasma near Phase Transition
Due to a rapid change of the entropy density across the critical
temperature of the QCD phase transition, the pressure and the
energy density above generally deviate from their Stefan-Boltzmann
values. We shall demonstrate this both analytically and numerically for a
general class of consistent with thermodynamical constraints and make a
qualitative comparison of the result with the lattice QCD data. Quantities
related to such as the specific heat and sound velocity are also
discussed.Comment: 6 pages revtex, 4 postscript figure
Canonical Timing and Spectral Behavior of LMC X-3 in the Low/Hard State
We present results from three observations with the Rossi X-ray Timing
Explorer (RXTE) of LMC X-3, obtained while the source was in an extended
'low/hard' state. The data reveal a hard X-ray spectrum which is well fit by a
pure power law with photon index Gamma=1.69+/-0.02, with a source luminosity at
50 kpc of 5-16x10^{36}erg/s (2--10 keV). Strong broad-band (0.01-100 Hz) time
variability is also observed, with fractional rms amplitude 40+/-4%, plus a
quasi-periodic oscillation (QPO) peak at 0.46+/-0.02 Hz with rms amplitude
\~14%. This is the first reported observation in which the full canonical
low/hard state behavior (pure hard power law spectrum combined with strong
broad-band noise and QPO) for LMC X-3 is seen. We reanalyze several archival
RXTE observations of LMC X-3 and derive consistent spectral and timing
parameters, and determine the overall luminosity variation between high/soft
and low/hard states. The timing and spectral properties of LMC X-3 during the
recurrent low/hard states are quantitatively similar to that typically seen in
the Galactic black hole candidates.Comment: 5 pages, 3 figures, accepted for ApJ Letter
How much laser power can propagate through fusion plasma?
Propagation of intense laser beams is crucial for inertial confinement
fusion, which requires precise beam control to achieve the compression and
heating necessary to ignite the fusion reaction. The National Ignition Facility
(NIF), where fusion will be attempted, is now under construction. Control of
intense beam propagation may be ruined by laser beam self-focusing. We have
identified the maximum laser beam power that can propagate through fusion
plasma without significant self-focusing and have found excellent agreement
with recent experimental data, and suggest a way to increase that maximum by
appropriate choice of plasma composition with implication for NIF designs. Our
theory also leads to the prediction of anti-correlation between beam spray and
backscatter and suggests the indirect control of backscatter through
manipulation of plasma ionization state or acoustic damping.Comment: 15 pages, 4 figures, submitted to Plasma Physics and Controlled
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