711 research outputs found
Hyperbolic Chaos of Turing Patterns
We consider time evolution of Turing patterns in an extended system governed
by an equation of the Swift-Hohenberg type, where due to an external periodic
parameter modulation long-wave and short-wave patterns with length scales
related as 1:3 emerge in succession. We show theoretically and demonstrate
numerically that the spatial phases of the patterns, being observed
stroboscopically, are governed by an expanding circle map, so that the
corresponding chaos of Turing patterns is hyperbolic, associated with a strange
attractor of the Smale-Williams solenoid type. This chaos is shown to be robust
with respect to variations of parameters and boundary conditions.Comment: 4 pages, 4 figure
Electric instability in superconductor-normal conductor ring
Non-linear electrodynamics of a ring-shaped Andreev interferometer
(superconductor-normal conductor-superconductor hybrid structure) inductively
coupled to a circuit of the dissipative current is investigated. The
current-voltage characteristics (CVC) is demonstrated to be a series of loops
with several branches intersecting in the CVC origin. The sensitivity of the
transport current to a change of the applied external magnetic flux can be
comparable to the one of the conventional SQUID's. Spontaneous arising of
coupled non-linear oscillations of the transport current, the Josephson current
and the magnetic flux in Andreev interferometers are also predicted and
investigated. The frequency of these oscillations can be varied in a wide
range, while the maximal frequency can reach
.Comment: 4 pages, 4 figure
Secondary electron emission yield in the limit of low electron energy
Secondary electron emission (SEE) from solids plays an important role in many
areas of science and technology.1 In recent years, there has been renewed
interest in the experimental and theoretical studies of SEE. A recent study
proposed that the reflectivity of very low energy electrons from solid surface
approaches unity in the limit of zero electron energy2,3,4, If this was indeed
the case, this effect would have profound implications on the formation of
electron clouds in particle accelerators,2-4 plasma measurements with
electrostatic Langmuir probes, and operation of Hall plasma thrusters for
spacecraft propulsion5,6. It appears that, the proposed high electron
reflectivity at low electron energies contradicts to numerous previous
experimental studies of the secondary electron emission7. The goal of this note
is to discuss possible causes of these contradictions.Comment: 3 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop
on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba,
Ital
Orbital stability of solutions to the problem on capillary-gravity waves in two-fluid layer
Going back to N. E. Kochin [1] problem about capillary-gravity waves on interface of
two-fluid flow is considered as bifurcation problem with spectral parameters
Spectral and polarization dependencies of luminescence by hot carriers in graphene
The luminescence caused by the interband transitions of hot carriers in
graphene is considered theoretically. The dependencies of emission in mid- and
near-IR spectral regions versus energy and concentration of hot carriers are
analyzed; they are determined both by an applied electric field and a gate
voltage. The polarization dependency is determined by the angle between the
propagation direction and the normal to the graphene sheet. The characteristics
of radiation from large-scale-area samples of epitaxial graphene and from
microstructures of exfoliated graphene are considered. The averaged over angles
efficiency of emission is also presented.Comment: 6 pages, 5 figure
Spin-thermo-electronic oscillator based on inverse giant magnetoresistance
A spin-thermo-electronic valve with the free layer of exchange-spring type
and inverse magnetoresistance is investigated. The structure has S-shaped
current-voltage characteristics and can exhibit spontaneous oscillations when
integrated with a conventional capacitor within a resonator circuit. The
frequency of the oscillations can be controlled from essentially dc to the GHz
range by the circuit capacitance.Comment: 7 pages, 9 figure
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