177 research outputs found
Asymmetric ac fluxon depinning in a Josephson junction array: A highly discrete limit
Directed motion and depinning of topological solitons in a strongly discrete
damped and biharmonically ac-driven array of Josephson junctions is studied.
The mechanism of the depinning transition is investigated in detail. We show
that the depinning process takes place through chaotization of an initially
standing fluxon periodic orbit. Detailed investigation of the Floquet
multipliers of these orbits shows that depending on the depinning parameters
(either the driving amplitude or the phase shift between harmonics) the
chaotization process can take place either along the period-doubling scenario
or due to the type-I intermittency.Comment: 12 pages, 9 figures. Submitted to Phys. Rev.
Boundary conditions for the states with resonant tunnelling across the -potential
The one-dimensional Schr\"odinger equation with the point potential in the
form of the derivative of Dirac's delta function, with
being a coupling constant, is investigated. This equation is known to
require an extension to the space of wave functions discontinuous at
the origin under the two-sided (at ) boundary conditions given through
the transfer matrix where . However, the recent studies, where a resonant
non-zero transmission across this potential has been established to occur on
discrete sets in the -space, contradict
to these boundary conditions used widely by many authors. The present
communication aims at solving this discrepancy using a more general form of
boundary conditions.Comment: Submitted Phys. Lett. A. Essentially revised and extended version, 1
figure added. 12 page
Ratchet device with broken friction symmetry
An experimental setup (gadget) has been made for demonstration of a ratchet mechanism induced by broken symmetry of a dependence of dry friction on external forcing. This gadget converts longitudinal oscillating or fluctuating motion into a unidirectional rotation, the direction of which is in accordance with given theoretical arguments. Despite the setup being three dimensional, the ratchet rotary motion is proved to be described by one simple dynamic equation. This kind of motion is a result of the interplay of friction and inertia
Bound states and point interactions of the one-dimensional pseudospin-one Hamiltonian
The spectrum of a one-dimensional pseudospin-one Hamiltonian with a
three-component potential is studied for two configurations: (i) all the
potential components are constants over the whole coordinate space and (ii) the
profile of some components is of a rectangular form. In case (i), it is
illustrated how the structure of three (lower, middle and upper) bands depends
on the configuration of potential strengths including the appearance of flat
bands at some special values of these strengths. In case (ii), the set of two
equations for finding bound states is derived. The spectrum of bound-state
energies is shown to depend crucially on the configuration of potential
strengths. Each of these configurations is specified by a single strength
parameter . The bound-state energies are calculated as functions of the
strength and a one-point approach is developed realizing correspondent
point interactions. For different potential configurations, the energy
dependence on the strength is described in detail, including its one-point
approximation. From a whole variety of bound-state spectra, four characteristic
types are singled out.Comment: To appear in Journal of Physics A: Mathematical and Theoretical. 11
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