67 research outputs found
Large-amplitude electron-acoustic solitons in a dusty plasma with kappa-distributed electrons
The Sagdeev pseudopotential method is used to investigate the occurrence and
the dynamics of fully nonlinear electrostatic solitary structures in a plasma
containing suprathermal hot electrons, in the presence of massive charged dust
particles in the background. The soliton existence domain is delineated, and
its parametric dependence on different physical parameters is clarified.Comment: 3 pages, 1 figure, presented as a poster at the 6th International
Conference on the Physics of Dusty Plasmas (ICPDP6), Garmisch-Partenkirchen,
Germany, 201
Higher-order effects and ultra-short solitons in left-handed metamaterials
Starting from Maxwell's equations, we use the reductive perturbation method
to derive a second-order and a third-order nonlinear Schroedinger equation,
describing ultra-short solitons in nonlinear left-handed metamaterials. We find
necessary conditions and derive exact bright and dark soliton solutions of
these equations for the electric and magnetic field envelopes.Comment: 4 pages, 2 figures, Phys. Rev. E in pres
Self-focusing and envelope pulse generation in nonlinear magnetic metamaterials
The self-modulation of waves propagating in nonlinear magnetic metamaterials
is investigated. Considering the propagation of a modulated amplitude magnetic
field in such a medium, we show that the self-modulation of the carrier wave
leads to a spontaneous energy localization via the generation of localized
envelope structures (envelope solitons), whose form and properties are
discussed. These results are also supported by numerical calculations.Comment: 4 pages 3 figure
Surge of power transmission in flat and nearly flat band lattices
Flat band systems can yield interesting phenomena, such as dispersion
suppression of waves with frequency at the band. While linear transport
vanishes, the corresponding nonlinear case is still an open question. Here, we
study power transmission along nonlinear sawtooth lattices due to waves with
the flat band frequency injected at one end. While there is no power transfer
for small intensity, there is a threshold amplitude above which a surge of
power transmission occurs, i.e., supratransmission, for defocusing
nonlinearity. This is due to a nonlinear evanescent wave with the flat band
frequency that becomes unstable. We show that dispersion suppression and
supratransmission also exist even when the band is nearly flat.Comment: 6 pages, 5 figure
T-wave Inversion through Inhomogeneous Voltage Diffusion within the FK3V Cardiac Model
The heart beats due to the synchronized contraction of cardiomyocytes
triggered by a periodic sequence of electrical signals called action
potentials, which originate in the sinoatrial node and spread through the
heart's electrical system. A large body of work is devoted to modeling the
propagation of the action potential and to reproducing reliably its shape and
duration. Connection of computational modeling of cells to macroscopic
phenomenological curves such as the electrocardiogram has been also intense,
due to its clinical importancce in analyzing cardiovascular diseases. In this
work we simulate the dynamics of action potential propagation using the
three-variable Fenton-Karma model that can account for both normal and damaged
cells through spatially inhomogeneous voltage diffusion coefficient. We monitor
the action potential propagation in the cardiac tissue and calculate the
pseudo-electrocardiogram that reproduces the R and T waves. The R wave
amplitude varies according to a double exponential law as a function of the
(spatially homogeneous, for an isotropic tissue) diffusion coefficient. The
addition of spatial inhomogeneity in the diffusion coefficient by means of a
defected region representing damaged cardiac cells, may result in T-wave
inversion in the calculated pseudo-electrocardiogram. The transition from
positive to negative polarity of the T-wave is analyzed as a function of the
length and the depth of the defected region.Comment: 12 pages, figures, 39 reference
Electron-acoustic plasma waves: oblique modulation and envelope solitons
Theoretical and numerical studies are presented of the amplitude modulation
of electron-acoustic waves (EAWs) propagating in space plasmas whose
constituents are inertial cold electrons, Boltzmann distributed hot electrons
and stationary ions. Perturbations oblique to the carrier EAW propagation
direction have been considered. The stability analysis, based on a nonlinear
Schroedinger equation (NLSE), reveals that the EAW may become unstable; the
stability criteria depend on the angle between the modulation and
propagation directions. Different types of localized EA excitations are shown
to exist.Comment: 10 pages, 5 figures; to appear in Phys. Rev.
Driven linear modes: Analytical solutions for finite discrete systems
We have obtained exact analytical expressions in closed form, for the linear
modes excited in finite and discrete systems that are driven by a spatially
homogeneous alternating field. Those modes are extended for frequencies within
the linear frequency band while they are either end-localized or end-avoided
for frequencies outside the linear frequency band. The analytical solutions are
resonant at particular frequencies, which compose the frequency dispersion
relation of the finite system.Comment: 4 pages, 3 figures, submitted to Phys. Rev.
Ion-acoustic envelope modes in a degenerate relativistic electron-ion plasma
A self-consistent relativistic two-fluid model is proposed for
one-dimensional electron-ion plasma dynamics. A multiple scales perturbation
technique is employed, leading to an evolution equation for the wave envelope,
in the form of a nonlinear Schr\"odinger type equation (NLSE). The inclusion of
relativistic effects is shown to introduce density-dependent factors, not
present in the non-relativistic case - in the conditions for modulational
instability. The role of relativistic effects on the linear dispersion laws and
on envelope soliton solutions of the NLSE is discussed.Comment: Submitted to Physics of Plasma
Nonlinear magnetoinductive transmission lines
Power transmission in one-dimensional nonlinear magnetic metamaterials driven
at one end is investigated numerically and analytically in a wide frequency
range. The nonlinear magnetic metamaterials are composed of varactor-loaded
split-ring resonators which are coupled magnetically through their mutual
inductances, forming thus a magnetoiductive transmission line. In the linear
limit, significant power transmission along the array only appears for
frequencies inside the linear magnetoinductive wave band. We present
analytical, closed form solutions for the magnetoinductive waves transmitting
the power in this regime, and their discrete frequency dispersion. When
nonlinearity is important, more frequency bands with significant power
transmission along the array may appear. In the equivalent circuit picture, the
nonlinear magnetoiductive transmission line driven at one end by a relatively
weak electromotive force, can be modeled by coupled
resistive-inductive-capacitive (RLC) circuits with voltage-dependent
capacitance. Extended numerical simulations reveal that power transmission
along the array is also possible in other than the linear frequency bands,
which are located close to the nonlinear resonances of a single nonlinear RLC
circuit. Moreover, the effectiveness of power transmission for driving
frequencies in the nonlinear bands is comparable to that in the linear band.
Power transmission in the nonlinear bands occurs through the linear modes of
the system, and it is closely related to the instability of a mode that is
localized at the driven site.Comment: 11 pages, 11 figures, submitted to International Journal of
Bifurcation and Chao
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