2,952 research outputs found
On the internal modes in sine-Gordon chain
We address the issue of internal modes of a kink of a discrete sine-Gordon
equation. The main point of the present study is to elucidate how the
antisymmetric internal mode frequency dependence enters the quasicontinuum
spectrum of nonlocalized waves. We analyze the internal frequency dependencies
as functions of both the number of cites and discreteness parameter and explain
the origin of spectrum peculiarity which arises after the frequency dependence
of antisymmetric mode returns back to the continuous spectrum at some nonzero
value of the intersite coupling.Comment: 5 pages, 3 figure
Scattering of vortex pairs in 2D easy-plane ferromagnets
Vortex-antivortex pairs in 2D easy-plane ferromagnets have characteristics of
solitons in two dimensions. We investigate numerically and analytically the
dynamics of such vortex pairs. In particular we simulate numerically the
head-on collision of two pairs with different velocities for a wide range of
the total linear momentum of the system. If the momentum difference of the two
pairs is small, the vortices exchange partners, scatter at an angle depending
on this difference, and form two new identical pairs. If it is large, the pairs
pass through each other without losing their identity. We also study head-tail
collisions. Two identical pairs moving in the same direction are bound into a
moving quadrupole in which the two vortices as well as the two antivortices
rotate around each other. We study the scattering processes also analytically
in the frame of a collective variable theory, where the equations of motion for
a system of four vortices constitute an integrable system. The features of the
different collision scenarios are fully reproduced by the theory. We finally
compare some aspects of the present soliton scattering with the corresponding
situation in one dimension.Comment: 13 pages (RevTeX), 8 figure
Group analysis and renormgroup symmetries
An original regular approach to constructing special type symmetries for
boundary value problems, namely renormgroup symmetries, is presented. Different
methods of calculating these symmetries, based on modern group analysis are
described. Application of the approach to boundary value problems is
demonstrated with the help of a simple mathematical model.Comment: 17 pages, RevTeX LATeX file, to appear in Journal of Mathematical
Physic
VLBI detection of the HST-1 feature in the M87 jet at 2 cm
A bright feature 80 pc away from the core in the powerful jet of M87 shows
highly unusual properties. Earlier radio, optical and X-ray observations have
shown that this feature, labeled HST-1, is superluminal, and is possibly
connected with the TeV flare detected by HESS in 2005. It has been claimed that
this feature might have a blazar nature, due to these properties. To examine
the possible blazar-like nature of HST-1, we analyzed lambda 2 cm VLBA archival
data from dedicated full-track observations and the 2 cm survey/MOJAVE VLBI
monitoring programs obtained between 2000 and 2009. Applying VLBI wide-field
imaging techniques, the HST-1 region was imaged at milliarcsecond resolution.
Here we present the first 2 cm VLBI detection of this feature in observations
from early 2003 to early 2007, and analyze its evolution over this time. Using
the detections of HST-1, we find that the projected apparent speed is 0.61 +/-
0.31 c. A comparison of the VLA and VLBA flux densities of this feature
indicate that is mostly resolved on molliarcsecond scales. This feature is
optically thin between lambda 2 cm and lambda 20 cm. We do not find evidence of
a blazar nature for HST-1.Comment: 9 pages, 9 figures, accepted by Astronomy and Astrophysic
Aharonov-Casher effect in a two dimensional hole gas with spin-orbit interaction
We study the quantum interference effects induced by the Aharonov-Casher
phase in a ring structure in a two-dimensional heavy hole (HH) system with
spin-orbit interaction realizable in narrow asymmetric quantum wells. The
influence of the spin-orbit interaction strength on the transport is
investigated analytically. These analytical results allow us to explain the
interference effects as a signature of the Aharonov-Casher Berry phases. Unlike
previous studies on the electron two-dimensional Rashba systems, we find that
the frequency of conductance modulations as a function of the spin-orbit
strength is not constant but increases for larger spin-orbit splittings. In the
limit of thin channel rings (width smaller than Fermi wavelength), we find that
the spin-orbit splitting can be greatly increased due to quantization in the
radial direction. We also study the influence of magnetic field considering
both limits of small and large Zeeman splittings.Comment: 6 pages, 4 figure
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