Results 1 - 10 of 18436
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[en] Negative plasma potentials were obtained in DC hot filament unmagnetized electropositive argon plasma for sufficiently low neutral pressure. Double layers provide ion and electron confinement near the walls. The potential profiles from the center of the plasma to the potential minima are quite similar in shape to those observed when the plasma has positive plasma potentials. The primary electrons emitted from the filaments are important for charge conservation and for modification of the Bohm criteria but are not important for current balance. -- Highlights: → Negative plasma potentials in plasmas that do not contain negative ions can exist. → They are non-monotonic and bounded by double layers. → It provides an explanation for unknown quality in hot filament discharges. → Theory and experiment for double layers are given. → Bohm speed modifications with the existence of external electrons are given.
[en] The concatenated cranking procedure (CCP) is exploited to resolve time-dependent quantum systems with different driving fields. We show that the scheme of CCP is able to achieve dynamical invariants for a couple of extended spin-1/2 models, by which the inconsistency of quantitative condition in the adiabatic theorem can be manifested conveniently. Furthermore, we propose a sectioned CCP scheme and apply it to resolve the time evolution for a modulated Landau-Zener model which cannot guarantee the convergency of the CCP in an overall evolution. -- Highlights: → We study time-dependent quantum systems by the concatenated cranking approach. → Dynamical invariants of a couple of extended spin-half models are derived. → Inconsistency of the quantitative condition in the adiabatic theorem is manifested. → We propose also a sectioned scheme to solve a modulated Landau-Zener model.
[en] We describe the radiation phenomena which can take place in the physical vacuum such as Cherenkov-type shock waves. Their macroscopical characteristics - cone angle, flash duration, radiation yield and spectral distribution - are computed. It turns out that the radiation yield is proportional to the square of the proper energy scale of the vacuum which serves also as the vacuum instability threshold and the natural ultraviolet cutoff. While the analysis is mainly based on the theory engaging the logarithmic nonlinear quantum wave equation, some of the obtained results must be valid for any Lorentz-invariance violating theory describing the vacuum by (effectively) continuous medium in the long-wavelength approximation. -- Highlights: The Cherenkov-type shock waves can take place in the physical vacuum. → Their macroscopical characteristics, cone angle, flash duration, radiation yield and spectral distribution, are computed. → The radiation yield is proportional to the square of the proper energy of the vacuum.
[en] We study higher order solutions of Lieb-Liniger integral equation for a one-dimensional δ-function Bose gas. By use of the power series expansion method, the integral equation is solved and the correction terms which improve the Bogoliubov theory are calculated analytically in the weak coupling regime. Physical quantities such as the ground state energy and the chemical potential are represented by a dimensionless parameter γ=c/ρ, where c is the interaction strength and ρ is the number density of particles while the quasi-momentum distribution function is expressed in terms of a dimensionless parameter λ=c/K, where K is the cut-off momentum. -- Highlights: → Exact analysis of a one-dimensional delta-function Bose gas for weak coupling case. → The third order corrections are given by the Bethe ansatz method explicitly for the first time. → The Lieb-Liniger equation is solved for the quasi-momentum distribution function. → The ground state energy and the chemical potential are obtained. → Some difference between the previous result and ours is pointed out.
[en] The detailed comparison between static (frozen core) and polarization radiation emission channel in electron-tungsten ions collisions is presented. Both Bremsstrahlung and radiative recombination spectra are calculated for different ion charges Zi and electron energies E. The consideration is based on quasiclassical approach using statistical (Thomas-Fermi) and local plasma frequency models for ion cores as well as rotational approximation for emission spectra. The frequency and energy domains where polarization channel is comparable or even dominates over static one are determined. The results are of interest for modern magnetic fusion investigations of plasmas with tungsten impurity. -- Highlights: → Static and polarization radiation in electron-tungsten ions collisions is investigated. → Both Bremsstrahlung and radiative recombination spectra are calculated. → Different ion charges and electron energies are taken into consideration. → We determine the ranges of parameters where polarization channel is important.
[en] A theoretical model is developed to study the sedimentation characteristics of nanoscale colloidal suspensions (nanofluids). The influences of various deterministic and stochastic forcing parameters in the transport characteristics of the suspended nanoparticles are investigated by employing a Langevin formalism of particle transport. The role of collective particle interaction phenomena in the sedimentation of nanoparticles is analyzed by invoking the fundamental considerations of agglomeration-deagglomeration kinetics of the particulate phases. The model demonstrates the effect of particle volume fraction, particle size, and aggregate structure on the sedimentation velocity of the suspended nanoparticles. Predictions from the present model agree well with the experimental results reported in the literature. -- Highlights: → Sedimentation characteristics of nanoscale colloidal suspensions are studied. → Effect of particle aggregation and break-up is considered. → Nonmonotonic variation of sedimentation velocity with particle volume fraction is obtained. → Numerical results compare well with experimental data reported in the literature.
[en] In this Letter we analyze the (im)possibility of the exact cloning of orthogonal three-qubit CAT states under local operation and classical communication (LOCC) with the help of a restricted entangled state. We also classify the three-qubit CAT states that can (not) be cloned under LOCC restrictions and extend the results to the n-qubit case. -- Highlights: → We analyze the (im)possibility of exact cloning of orthogonal CAT states under LOCC. → We also classify the set of CAT states that can(not) be cloned by LOCC. → No set of orthogonal CAT states can be cloned by LOCC with help of similar CAT state. → Any two orthogonal n-qubit GHZ-states can be cloned by LOCC with help of a GHZ state.