707 research outputs found
Spectra of Field Fluctuations in Braneworld Models with Broken Bulk Lorentz Invariance
We investigate five-dimensional braneworld setups with broken Lorentz
invariance continuing the developments of our previous paper (arXiv:0712.1136),
where a family of static self-tuning braneworld solutions was found. We show
that several known braneworld models can be embedded into this family. Then we
give a qualitative analysis of spectra of field fluctuations in backgrounds
with broken Lorentz invariance. We also elaborate on one particular model and
study spectra of scalar and spinor fields in it. It turns out that the spectra
we have found possess very peculiar and unexpected properties.Comment: 30 pages, 8 figures, minor corrections, references added, note adde
Homoclinic standing waves in focussing DNLS equations --Variational approach via constrained optimization
We study focussing discrete nonlinear Schr\"{o}dinger equations and present a
new variational existence proof for homoclinic standing waves (bright
solitons). Our approach relies on the constrained maximization of an energy
functional and provides the existence of two one-parameter families of waves
with unimodal and even profile function for a wide class of nonlinearities.
Finally, we illustrate our results by numerical simulations.Comment: new version with revised introduction and improved condition (A3); 16
pages, several figure
Pecularities of Hall effect in GaAs/{\delta}<Mn>/GaAs/In\timesGa1-\timesAs/GaAs (\times {\approx} 0.2) heterostructures with high Mn content
Transport properties of GaAs/{\delta}/GaAs/In\timesGa1-\timesAs/GaAs
structures containing InxGa1-xAs (\times {\approx} 0.2) quantum well (QW) and
Mn delta layer (DL) with relatively high, about one Mn monolayer (ML) content,
are studied. In these structures DL is separated from QW by GaAs spacer with
the thickness ds = 2-5 nm. All structures possess a dielectric character of
conductivity and demonstrate a maximum in the resistance temperature dependence
Rxx(T) at the temperature {\approx} 46K which is usually associated with the
Curie temperature Tc of ferromagnetic (FM) transition in DL. However, it is
found that the Hall effect concentration of holes pH in QW does not decrease
below TC as one ordinary expects in similar systems. On the contrary, the
dependence pH(T) experiences a minimum at T = 80-100 K depending on the spacer
thickness, then increases at low temperatures more strongly than ds is smaller
and reaches a giant value pH = (1-2)\cdot10^13 cm^(-2). Obtained results are
interpreted in the terms of magnetic proximity effect of DL on QW, leading to
induce spin polarization of the holes in QW. Strong structural and magnetic
disorder in DL and QW, leading to the phase segregation in them is taken into
consideration. The high pH value is explained as a result of compensation of
the positive sign normal Hall effect component by the negative sign anomalous
Hall effect component.Comment: 19 pages, 6 figure
Action minimizing fronts in general FPU-type chains
We study atomic chains with nonlinear nearest neighbour interactions and
prove the existence of fronts (heteroclinic travelling waves with constant
asymptotic states). Generalizing recent results of Herrmann and Rademacher we
allow for non-convex interaction potentials and find fronts with non-monotone
profile. These fronts minimize an action integral and can only exists if the
asymptotic states fulfil the macroscopic constraints and if the interaction
potential satisfies a geometric graph condition. Finally, we illustrate our
findings by numerical simulations.Comment: 19 pages, several figure
Role of beam polarization in the determination of and couplings from
We evaluate the constraints on anomalous trilinear gauge-boson couplings that
can be obtained from the study of electron-positron annihilation into pairs
at a facility with either the electron beam longitudinally polarized or both
electron and positron beams transversely polarized. The energy ranges
considered in the analysis are the ones relevant to the next-linear collider
and to LEP~200. We discuss the possibilities of a model independent analysis of
the general conserving anomalous effective Lagrangian, as well as its
restriction to some specific models with reduced number of independent
couplings. The combination of observables with initial and final state
polarizations allows to separately constrain the different couplings and to
improve the corresponding numerical bounds.Comment: 24 pages, LaTeX, 9 figures (available on request from the authors
Psychological profile in noise-induced hearing loss patients: a pilot study
Introduction. Noise-induced hearing loss is a rather prevalent condition and can be distressing for a substantial proportion of patients, although researches describing psychological characteristics in noise-induced occupational hearing loss patients are not numerous.The study aims to find the effects of occupational noise on the psychological status among noise-induced hearing loss (NIHL) patients.Methods. Two groups, cross-sectional design. Study sample: 44 occupational noiseinduced male forming NIHL patients group (n = 21) and a control group (n = 23). Both groups were tested using the Russian versions of psychological questionnaires.Results. Almost one third of NIHL patients are the highly anxiety individuals as compared with the healthy participants (p < 0.01). Mixed type of response to the surrounding reality combined a high need for self-actualization with high self-control, tendency to inhibit and restrain behavioral reactions, in this case it is possible to “overlap” both neurotic and behavioral responses, which can affect the general overstrain and manifest by the somatization of the internal conflict. In general, NIHL patients use constructive cognitive, emotional and behavioral coping strategies. Patients use both constructive and tense defense mechanisms. Conclusion. It has been established that in patients with NIHL, in comparison with practically healthy persons, tension accumulates, and a tendency to psychotraumatization appears. However, it is currently difficult to determine whether NIHL is a predisposing factor for these psychological characteristics, so further research is needed to determine how significant this relationship is. Key words: noise-induced hearing loss, occupational noise, psychological profile>˂ 0.01). Mixed type of response to the surrounding reality combined a high need for self-actualization with high self-control, tendency to inhibit and restrain behavioral reactions, in this case it is possible to “overlap” both neurotic and behavioral responses, which can affect the general overstrain and manifest by the somatization of the internal conflict. In general, NIHL patients use constructive cognitive, emotional and behavioral coping strategies. Patients use both constructive and tense defense mechanisms.Conclusion. It has been established that in patients with NIHL, in comparison with practically healthy persons, tension accumulates, and a tendency to psychotraumatization appears. However, it is currently difficult to determine whether NIHL is a predisposing factor for these psychological characteristics, so further research is needed to determine how significant this relationship is
Quantum spin chains with site dissipation
We use Monte Carlo simulations to study chains of Ising- and XY-spins with
dissipation coupling to the site variables. The phase diagram and critical
exponents of the dissipative Ising chain in a transverse magnetic field have
been computed previously, and here we consider a universal ratio of
susceptibilities. We furthermore present the phase diagram and exponents of the
dissipative XY-chain, which exhibits a second order phase transition. All our
results compare well with the predictions from a dissipative field
theory
Translationally invariant nonlinear Schrodinger lattices
Persistence of stationary and traveling single-humped localized solutions in
the spatial discretizations of the nonlinear Schrodinger (NLS) equation is
addressed. The discrete NLS equation with the most general cubic polynomial
function is considered. Constraints on the nonlinear function are found from
the condition that the second-order difference equation for stationary
solutions can be reduced to the first-order difference map. The discrete NLS
equation with such an exceptional nonlinear function is shown to have a
conserved momentum but admits no standard Hamiltonian structure. It is proved
that the reduction to the first-order difference map gives a sufficient
condition for existence of translationally invariant single-humped stationary
solutions and a necessary condition for existence of single-humped traveling
solutions. Other constraints on the nonlinear function are found from the
condition that the differential advance-delay equation for traveling solutions
admits a reduction to an integrable normal form given by a third-order
differential equation. This reduction also gives a necessary condition for
existence of single-humped traveling solutions. The nonlinear function which
admits both reductions defines a two-parameter family of discrete NLS equations
which generalizes the integrable Ablowitz--Ladik lattice.Comment: 24 pages, 4 figure
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