1,798 research outputs found
Mass Transfer Mechanism in Real Crystals by Pulsed Laser Irradiation
The dynamic processes in the surface layers of metals subjected activity of a
pulsing laser irradiation, which destroyed not the crystalline structure in
details surveyed. The procedure of calculation of a dislocation density
generated in bulk of metal during the relaxation processes and at repeated
pulse laser action is presented. The results of evaluations coincide with high
accuracy with transmission electron microscopy dates. The
dislocation-interstitial mechanism of laser-stimulated mass-transfer in real
crystals is presented on the basis of the ideas of the interaction of structure
defects in dynamically deforming medium. The good compliance of theoretical and
experimental results approves a defining role of the presented mechanism of
mass transfer at pulse laser action on metals. The possible implementation this
dislocation-interstitial mechanism of mass transfer in metals to other cases of
pulsing influences is justifiedComment: 10 pages, 2 figures, Late
Analytic model for a frictional shallow-water undular bore
We use the integrable Kaup-Boussinesq shallow water system, modified by a
small viscous term, to model the formation of an undular bore with a steady
profile. The description is made in terms of the corresponding integrable
Whitham system, also appropriately modified by friction. This is derived in
Riemann variables using a modified finite-gap integration technique for the
AKNS scheme. The Whitham system is then reduced to a simple first-order
differential equation which is integrated numerically to obtain an asymptotic
profile of the undular bore, with the local oscillatory structure described by
the periodic solution of the unperturbed Kaup-Boussinesq system. This solution
of the Whitham equations is shown to be consistent with certain jump conditions
following directly from conservation laws for the original system. A comparison
is made with the recently studied dissipationless case for the same system,
where the undular bore is unsteady.Comment: 24 page
Suppression of transverse instabilities of dark solitons and their dispersive shock waves
We investigate the impact of nonlocality, owing to diffusive behavior, on
transverse instabilities of a dark stripe propagating in a defocusing cubic
medium. The nonlocal response turns out to have a strongly stabilizing effect
both in the case of a single soliton input and in the regime where dispersive
shock waves develop "multisoliton regime". Such conclusions are supported by
the linear stability analysis and numerical simulation of the propagation
Whitham systems and deformations
We consider the deformations of Whitham systems including the "dispersion
terms" and having the form of Dubrovin-Zhang deformations of Frobenius
manifolds. The procedure is connected with B.A. Dubrovin problem of
deformations of Frobenius manifolds corresponding to the Whitham systems of
integrable hierarchies. Under some non-degeneracy requirements we suggest a
general scheme of the deformation of the hyperbolic Whitham systems using the
initial non-linear system. The general form of the deformed Whitham system
coincides with the form of the "low-dispersion" asymptotic expansions used by
B.A. Dubrovin and Y. Zhang in the theory of deformations of Frobenius
manifolds.Comment: 27 pages, Late
Runaway Quarks
When heavy nuclei collide, a quark-gluon plasma is formed. The plasma is
subject to strong electric field due to the charge of the colliding nuclei. The
electric field can influence the behavior of the quark-gluon plasma. In
particular, we might observe an increased number of quarks moving in the
direction of that field, as we do in the standard electron-ion plasma. In this
paper we show that this phenomenon, called the runaway quarks, does not exist.Comment: 13 pages, uses harvmac.tex, epsf.te
Thermal Fluctuations of the Electric Field in the Presence of Carrier Drift
We consider a semiconductor in a non-equilibrium steady state, with a dc
current. On top of the stationary carrier motion there are fluctuations. It is
shown that the stationary motion of the carriers (i.e., their drift) can have a
profound effect on the electromagnetic field fluctuations in the bulk of the
sample as well as outside it, close to the surface (evanescent waves in the
near field). The effect is particularly pronounced near the plasma frequency.
This is because drift leads to a significant modification of the dispersion
relation for the bulk and surface plasmons.Comment: Comments are welcom
Magnetic cloaking by a paramagnet/superconductor cylindrical tube in the critical state
Cloaking of static magnetic fields by a finite thickness type-II
superconductor tube being in the full critical state and surrounded by a
coaxial paramagnet shell is studied. On the basis of exact solutions to the
Maxwell equations, it is shown that, additionally to previous studies assuming
the Meissner state of the superconductor constituent, perfect cloaking is still
realizable at fields higher than the field of full flux penetration into the
superconductor and for arbitrary geometrical parameters of both constituents.
It is also proven that simultaneously the structure is fully undetectable under
the cloaking conditions. Differently from the case of the Meissner state the
cloaking properties in the application relevant critical state are realized,
however, only at a certain field magnitude.Comment: 5 pages, 4 figures; to be published in Applied Physics Letters. arXiv
admin note: substantial text overlap with arXiv:1401.356
Theory of shot noise in space-charge limited diffusive conduction regime
As is well known, the fluctuations from a stable stationary nonequilibrium
state are described by a linearized nonhomogeneous Boltzmann-Langevin equation.
The stationary state itself may be described by a nonlinear Boltzmann equation.
The ways of its linearization sometimes seem to be not unique. We argue that
there is actually a unique way to obtain a linear equation for the
fluctuations. In the present paper we treat as an example an analytical theory
of nonequilibrium shot noise in a diffusive conductor under the space charge
limited regime. Our approach is compared with that of Schomerus, Mishchenko and
Beenakker [Phys. Rev. B 60, 5839 (1999)]. We find some difference between the
present theory and the approach of their paper and discuss a possible origin of
the difference. We believe that it is related to the fundamentals of the theory
of fluctuation phenomena in a nonequilibrium electron gas.Comment: 17 pages, no figure
Critical density of a soliton gas
We quantify the notion of a dense soliton gas by establishing an upper bound
for the integrated density of states of the quantum-mechanical Schr\"odinger
operator associated with the KdV soliton gas dynamics. As a by-product of our
derivation we find the speed of sound in the soliton gas with Gaussian spectral
distribution function.Comment: 7 page
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