2,846 research outputs found
Exact Moving and Stationary Solutions of a Generalized Discrete Nonlinear Schrodinger Equation
We obtain exact moving and stationary, spatially periodic and localized
solutions of a generalized discrete nonlinear Schr\"odinger equation. More
specifically, we find two different moving periodic wave solutions and a
localized moving pulse solution. We also address the problem of finding exact
stationary solutions and, for a particular case of the model when stationary
solutions can be expressed through the Jacobi elliptic functions, we present a
two-point map from which all possible stationary solutions can be found.
Numerically we demonstrate the generic stability of the stationary pulse
solutions and also the robustness of moving pulses in long-term dynamics.Comment: 22 pages, 7 figures, to appear in J. Phys.
The anisotropic Heisenberg chain in coexisting transverse and longitudinal magnetic fields
The one-dimensional spin-1/2 model in a mixed transverse and
longitudinal magnetic field is studied. Using the specially developed version
of the mean-field approximation the order-disorder transition induced by the
magnetic field is investigated. The ground state phase diagram is obtained. The
behavior of the model in low transverse field is studied on the base of
conformal field theory. The relevance of our results to the observed phase
transition in the quasi-one-dimensional antiferromagnet is
discussed.Comment: 18 pages, 6 figure
Multi-field approach in mechanics of structural solids
We overview the basic concepts, models, and methods related to the
multi-field continuum theory of solids with complex structures. The multi-field
theory is formulated for structural solids by introducing a macrocell
consisting of several primitive cells and, accordingly, by increasing the
number of vector fields describing the response of the body to external
factors. Using this approach, we obtain several continuum models and explore
their essential properties by comparison with the original structural models.
Static and dynamical problems as well as the stability problems for structural
solids are considered. We demonstrate that the multi-field approach gives a way
to obtain families of models that generalize classical ones and are valid not
only for long-, but also for short-wavelength deformations of the structural
solid. Some examples of application of the multi-field theory and directions
for its further development are also discussed.Comment: 25 pages, 18 figure
Angular distributions in decays
The differential decay rates of the processes and
close to the threshold are calculated with
the help of the optical potential. The same calculations are made
for the decays of . We use the potential which has been suggested to
fit the cross sections of scattering together with and
six pion production in annihilation close to the
threshold. The invariant mass spectra is in agreement with the
available experimental data. The anisotropy of the angular distributions, which
appears due to the tensor forces in the interaction, is predicted
close to the threshold. This anisotropy is large enough to be
investigated experimentally. Such measurements would allow one to check the
accuracy of the model of interaction.Comment: 10 pages, 8 figure
AC Josephson properties of phase slip lines in wide tin films
Current steps in the current-voltage characteristics of wide superconducting
Sn films exposed to a microwave irradiation were observed in the resistive
state with phase slip lines. The behaviour of the magnitude of the steps on the
applied irradiation power was found to be similar to that for the current steps
in narrow superconducting channels with phase slip centers and, to some extent,
for the Shapiro steps in Josephson junctions. This provides evidence for the
Josephson properties of the phase slip lines in wide superconducting films and
supports the assumption about similarity between the processes of phase slip in
wide and narrow films.Comment: 7 pages, 2 figures, to be published in Supercond. Sci. Techno
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