16,001 research outputs found
Localization of Electromagnetic Fields in Disordered Fano Metamaterials
We present the first study of disorder in planar metamaterials consisting of
strongly interacting metamolecules, where coupled electric dipole and magnetic
dipole modes give rise to a Fano-type resonant response and show that
positional disorder leads to light localization inherently linked to collective
magnetic dipole excitations. We demonstrate that the magnetic excitation
persists in disordered arrays and results in the formation of "magnetic
hot-spots"
Analytical solution of two-layer beam taking into account interlayer slip and shear deformation
A mathematical model is proposed and its analytical solution derived for the analysis of the geometrically and materially linear two-layer beams with different material and geometric characteristics of an individual layer. The model takes into account the effect of the transverse shear deformation on displacements in each layer. The analytical study is carried out to evaluate the influence of the transverse shear deformation on the static and kinematic quantities. We study a simply supported two-layer planar beam subjected to the uniformly distributed load. Parametric studies have been performed to investigate the influence of shear by varying material and geometric parameters, such as interlayer slip modulus (K), flexural-to-shear moduli ratios (E/G) and span-to-depth ratios (L/h). The comparison of the results for vertical deflections shows that shear deformations are more important for high slip modulus, for ``short'' beams with small L/h ratios, and beams with high E/G ratios. In these cases, the effect of the shear deformations becomes significant and has to be addressed in design. It also becomes apparent that models, which consider the partial interaction between the layers, should be employed if beams have very flexible connections
Giant fluctuations of topological charge in a disordered wave guide
We study the fluctuations of the total topological charge of a scalar wave
propagating in a hollow conducting wave guide filled with scatterers inside. We
investigate the dependence of the screening on the scattering mean free path
and on the presence of boundaries. Near the cut-off frequencies of the wave
guide, screening is strongly suppressed near the boundaries. The resulting huge
fluctuations of the total topological charge are very sensitive to the
disorder.Comment: 8 pages 5 figures, submitted to Waves in Random and Complex Medi
Systematic study of proton-neutron pairing correlations in the nuclear shell model
A shell-model study of proton-neutron pairing in shell nuclei using a
parametrized hamiltonian that includes deformation and spin-orbit effects as
well as isoscalar and isovector pairing is reported. By working in a
shell-model framework we are able to assess the role of the various modes of
proton-neutron pairing in the presence of nuclear deformation without violating
symmetries. Results are presented for Ti, Ti, Ti, V
and Cr to assess how proton-neutron pair correlations emerge under
different scenarios. We also study how the presence of a one-body spin-obit
interaction affects the contribution of the various pairing modes.Comment: 12 pages, 16 figure
Disengaging and rehabilitating high-value detainees: a small scale qualitative study
In an era of international terrorism, interviews with high-value detainees may have the dual purpose of extracting useful information and of disengagement. We conducted a small-scale, qualitative study using in-depth, individual interviews with 11 experienced interviewers in the Southeast Asia region and Australia, in order to provide insights into the types of interviewing strategies employed in terrorist rehabilitation. Our findings highlight the potential efficacy of creating a physically comfortable and relaxed interview setting, and of using interview strategies that focus on rapport-building, principles of social persuasion and elements of procedural justice, along with a patient and flexible stance to questioning. We suggest that interviewers performing rehabilitation interviews with high-value detainees ought to be trained to use the social approach to interviewing
Thermal Bogoliubov transformation in nuclear structure theory
Thermal Bogoliubov transformation is an essential ingredient of the thermo
field dynamics -- the real time formalism in quantum field and many-body
theories at finite temperatures developed by H. Umezawa and coworkers. The
approach to study properties of hot nuclei which is based on the extension of
the well-known Quasiparticle-Phonon Model to finite temperatures employing the
TFD formalism is presented. A distinctive feature of the QPM-TFD combination is
a possibility to go beyond the standard approximations like the thermal
Hartree-Fock or the thermal RPA ones.Comment: 8 pages, Proceedings of the International Bogolyubov Conference
"Problems of Theoretical and Mathematical Physics", August 23 -- 27, 2009,
Dubna, Russi
Transverse rotation of the momentary field distribution and the orbital angular momentum of a light beam
The transverse beam pattern, usually observed in experiment, is a result of
averaging the optical-frequency oscillations of the electromagnetic field
distributed over the beam cross section. An analytical criterion is derived
that these oscillations are coupled with a sort of rotation around the beam
axis. This criterion appears to be in direct relation with the usual definition
of the beam orbital angular momentum.Comment: 9 pages, 1 figure with animatio
Dilute Bose gas with correlated disorder: A Path Integral Monte Carlo study
We investigate the thermodynamic properties of a dilute Bose gas in a
correlated random potential using exact path integral Monte Carlo methods. The
study is carried out in continuous space and disorder is produced in the
simulations by a 3D speckle pattern with tunable intensity and correlation
length. We calculate the shift of the superfluid transition temperature due to
disorder and we highlight the role of quantum localization by comparing the
critical chemical potential with the classical percolation threshold. The
equation of state of the gas is determined in the regime of strong disorder,
where superfluidity is suppressed and the normal phase exists down to very low
temperatures. We find a dependence of the energy in agreement with the
expected behavior in the Bose glass phase. We also discuss the major role
played by the disorder correlation length and we make contact with a
Hartree-Fock mean-field approach that holds valid if the correlation length is
very large. The density profiles are analyzed as a function of temperature and
interaction strength. Effects of localization and the depletion of the order
parameter are emphasized in the comparison between local condensate and total
density. At very low temperature we find that the energy and the particle
distribution of the gas are very well described by the T=0 Gross-Pitaevskii
theory even in the regime of very strong disorder.Comment: 27 pages, 20 figure
Structure of the vacuum states in the presence of isovector and isoscalar pairing correlations
The long standing problem of proton-neutron pairing and, in particular, the
limitations imposed on the solutions by the available symmetries, is revisited.
We look for solutions with non-vanishing expectation values of the proton, the
neutron and the isoscalar gaps. For an equal number of protons and neutrons we
find two solutions where the absolute values of proton and neutrons gaps are
equal but have the same or opposite sign. The behavior and structure of these
solutions differ for spin saturated (single l-shell) and spin unsaturared
systems (single j-shell). In the former case the BCS results are checked
against an exact calculation.Comment: 19 pages, 5 postscript figure
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