16 research outputs found
Nonlinear symmetry breaking of Aharonov-Bohm cages
We study the influence of mean field cubic nonlinearity on Aharonov-Bohm
caging in a diamond lattice with synthetic magnetic flux. For sufficiently weak
nonlinearities the Aharonov-Bohm caging persists as periodic nonlinear
breathing dynamics. Above a critical nonlinearity, symmetry breaking induces a
sharp transition in the dynamics and enables stronger wavepacket spreading.
This transition is distinct from other flatband networks, where continuous
spreading is induced by effective nonlinear hopping or resonances with
delocalized modes, and is in contrast to the quantum limit, where two-particle
hopping enables arbitrarily large spreading. This nonlinear symmetry breaking
transition is readily observable in femtosecond laser-written waveguide arrays.Comment: 6 pages, 5 figure
Composite localized modes in discretized spin-orbit-coupled Bose-Einstein condensates
We introduce a discrete model for binary spin-orbit-coupled (SOC)
Bose-Einstein condensates (BEC) trapped in a deep one-dimensional optical
lattice. Two different types of the couplings are considered, with spatial
derivatives acting inside each species, or between the species. The discrete
system with inter-site couplings dominated by the SOC, while the usual hopping
is negligible, \textit{emulates} condensates composed of extremely heavy atoms,
as well as those with opposite signs of the effective atomic masses in the two
components.\ Stable localized composite states of miscible and immiscible types
are constructed. The effect of the SOC on the immiscibility-miscibility
transition in the localized complexes, which emulates the phase transition
between insulating and conducting states in semiconductors, is studied.Comment: Journal of Physics B , in pres
Nonlinear gap modes and compactons in a lattice model for spin-orbit coupled exciton-polaritons in zigzag chains
We consider a system of generalized coupled Discrete Nonlinear
Schr\"{o}dinger (DNLS) equations, derived as a tight-binding model from the
Gross-Pitaevskii-type equations describing a zigzag chain of weakly coupled
condensates of exciton-polaritons with spin-orbit (TE-TM) coupling. We focus on
the simplest case when the angles for the links in the zigzag chain are with respect to the chain axis, and the basis (Wannier) functions are
cylindrically symmetric (zero orbital angular momenta). We analyze the
properties of the fundamental nonlinear localized solutions, with particular
interest in the discrete gap solitons appearing due to the simultaneous
presence of spin-orbit coupling and zigzag geometry, opening a gap in the
linear dispersion relation. In particular, their linear stability is analyzed.
We also find that the linear dispersion relation becomes exactly flat at
particular parameter values, and obtain corresponding compact solutions
localized on two neighboring sites, with spin-up and spin-down parts
out of phase at each site. The continuation of these compact modes into
exponentially decaying gap modes for generic parameter values is studied
numerically, and regions of stability are found to exist in the lower or upper
half of the gap, depending on the type of gap modes.Comment: 18 pages, 11 figures. Revised version with minor additions to text
and reference list. To be published in Journal of Physics Communication
Monte Carlo Calculation of the Energy Response Characteristics of a RadFET Radiation Detector
The Metal -Oxide Semiconductor Field-Effect-Transistor (MOSFET, RadFET) is frequently used as a sensor of ionizing radiation in nuclear-medicine, diagnostic-radiology, radiotherapy quality-assurance and in the nuclear and space industries. We focused our investigations on calculating the energy response of a p-type RadFET to low-energy photons in range from 12 keV to 2 MeV and on understanding the influence of uncertainties in the composition and geometry of the device in calculating the energy response function. All results were normalized to unit air kerma incident on the RadFET for incident photon energy of 1.1 MeV. The calculations of the energy response characteristics of a RadFET radiation detector were performed via Monte Carlo simulations using the MCNPX code and for a limited number of incident photon energies the FOTELP code was also used for the sake of comparison. The geometry of the RadFET was modeled as a simple stack of appropriate materials. Our goal was to obtain results with statistical uncertainties better than 1% (fulfilled in MCNPX calculations for all incident energies which resulted in simulations with 1 - 2x10(9) histories.13th IMEKO TC1-TC7 Joint Symposium Without Measurement No Science, Without Science No Measurement, Sep 01-03, 2010, City Univ London, London, Englan
Propagation of light in photonic lattices with saturable nonlinearity comprising a defect
Nonlinear gap modes and compactons in a lattice model for spin-orbit coupled exciton-polaritons in zigzag chains
Dynamics of dark solitons localized at structural defect in one-dimensional photonic lattices with defocusing saturable nonlinearity
A novel mobile transtelephonic system with synthesized 12-lead ECG
The problem of synthesizing the standard 12-lead electrocardiogram (ECG) from the signals recorded using three special ECG leads is studied in detail. The implementation of that concept into the design of a new mobile ECG transtelephonic system is presented. The system has two separate units: a stationary diagnostic-calibration center and a mobile ECG device with integrated electrodes. The patient records by himself three special leads with the mobile ECG recorder and sends data via cellular phone to the personal computer in the diagnostic center where standard 12-lead ECG is numerically reconstructed on the base of the patient transformation matrix previously calculated into the calibration process. The experimental study shows high accuracy of the reconstructed ECG