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991.
The non-cutoff Boltzmann equation can be simulated using the DSMC method, by a truncation of the collision term. However,
even for computing stationary solutions this may be very time consuming, in particular in situations far from equilibrium.
By adding an appropriate diffusion, to the DSMC-method, the rate of convergence when the truncation is removed, may be greatly
improved. We illustrate the technique on a toy model, the Kac equation, as well as on the full Boltzmann equation in a special
case. 相似文献
992.
Schürmann’s theory of quantum Lévy processes, and more generally the theory of quantum stochastic convolution cocycles, is
extended to the topological context of compact quantum groups and operator space coalgebras. Quantum stochastic convolution
cocycles on a C*-hyperbialgebra, which are Markov-regular, completely positive and contractive, are shown to satisfy coalgebraic quantum
stochastic differential equations with completely bounded coefficients, and the structure of their stochastic generators is
obtained. Automatic complete boundedness of a class of derivations is established, leading to a characterisation of the stochastic
generators of *-homomorphic convolution cocycles on a C*-bialgebra. Two tentative definitions of quantum Lévy process on a compact quantum group are given and, with respect to both
of these, it is shown that an equivalent process on Fock space may be reconstructed from the generator of the quantum Lévy
process. In the examples presented, connection to the algebraic theory is emphasised by a focus on full compact quantum groups. 相似文献
993.
994.
The Wigner function and the symplectic tomogram of an entangled quantum state, which is a superposition of the photon’s coherent
states (even and odd coherent states), is studied. Photon statistics and violation of Bell’s inequality for the photon state
are discussed. 相似文献
995.
Duan Yan-min Li Ai-hong Chen Jing Zhu Hai-yong Zhang Ge Huang Cheng-hui Wei Yong Huang Ling-xiong Qiu Yi-shen 《Journal of Russian Laser Research》2008,29(3):268-273
We report an LD-end-pumped linearly-polarized continuous-wave (CW) Nd:YAP laser operating at 1341.4 nm. Making use of the
plane-concave resonator (T = 2.4%) and the plane-plane resonator (T = 2.6%), we obtain linearly-polarized laser radiation at 1341.4 nm with a power of 3.15 and 2.86 W and corresponding optical
slope efficiency of 18.4 and 17.5%, respectively. The effect of the laser oscillation mode on the output is analyzed. An experiment
on the intra-cavity frequency doubling with an LBO crystal has been performed, and a laser power of 431 mW in one direction
at 670.7 nm was obtained. 相似文献
996.
The electronic energy-band structure, density of states (DOS), and optical properties of AgBO3 in the paraelectric cubic phase have been studied by using density functional theory within the local density approximation
for exchange-correlation for the first time. The band structure shows a band gap of 1.533 eV (AgNbO3)and 1.537 eV (AgTaO3)at (M-⌈)point in the Brillouin zone. The optical spectra of AgBO3 in the photon energy range up to 30 eV are investigated under the scissor approximation. The real and imaginary parts of
the dielectric function and — thus the optical constants such as reflectivity, absorption coefficient, electron energy-loss
function, refractive index, and extinction coefficient — are calculated. We have also made some comparisons with related experimental
and theoretical data that is available.
相似文献
997.
F. Martinez-Pinon J. A. Alvarez-Chavez D. Jaramillo-Vigueras L. de la Cruz-May H. L. Offerhaus 《Laser Physics》2008,18(11):1340-1343
Results on high radiance Yb3+-doped fiber lasers with novel double innerclad structures (double-D clad and four hole) and polarized output at ≈1090 nm are presented. We have demonstrated >40% of the total output power being polarized, making the fiber laser suitable for LIDAR and second-harmonic generation (SHG) applications. It also showed a 10-nm tuning range with low (less than 10 mW) average power variations. The narrow linewidth source was pumped with a low cost, low brightness laser diode, and exhibited a relatively low slope efficiency, which gives room for improvement by using a 976-nm pump source where Yb3+ has a narrower linewidth and at least five times higher absorption. 相似文献
998.
We solve the general problem of mixing of electromagnetic and scalar or pseudoscalar fields coupled by axion-type interactions
L
int = g
ϕ
ϕε
μναβ
F
μν
F
αβ
. The problem depends on several dimensionful scales, including the magnitude and direction of background magnetic field,
the pseudoscalar mass, plasma frequency, propagation frequency, wave number, and finally the pseudoscalar coupling. We apply
the results to the first consistent calculations of the mixing of light propagating in a background magnetic field of varying
directions, which show a great variety of fascinating resonant and polarization effects.
相似文献
999.
Direct Numerical Simulation (DNS) of decaying isotropic 3D magnetohydrodynamic (MHD) turbulence based on the 10243-modes in a periodic box is used to study the statistical properties of turbulence. In this paper, the presence of intermittency in MHD turbulence is investigated through the analysis of the Probability Distribution Function (PDF) for Elsässer fields and total energy fluctuations. We observe that the PDFs of the Elsässer fields fluctuations display a strong non-Gaussian behavior at small scale, which can be ascribed to multifractality feature, while the PDFs of the total energy fluctuations have the same shape over all observed scales and are monofractal. The PDFs have stretched exponential tail and satisfy the function P(|δX|) ~ exp(?A|δX| μ ). Numerically, we extract the exponent μ and find that it is constant for monofractal behavior as the length scale varies. To check the notion of self-similarity in the respective fluctuation, we apply the compensated structure functions. 相似文献
1000.
Sumana Chakraborty Yew Kam Ho 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):59-65
This work presents an investigation on the doubly excited 1S
e
autoionizing states of screened helium atom lying below the n = 4 threshold of the He+ ion. The potential generated in this system is represented by a Yukawa type potential. We have employed complex-coordinate
rotation method, as it is a powerful scheme to study high lying resonances. Hylleraas type wave function is used to consider
the correlation effect between all the charged particles. Our resonance parameters for the resonances lying below the He+ (n = 2) threshold agree well with those of the existing calculations by using the stabilization method. Resonances associated
with higher thresholds are new calculations. All the present results are well converged with basis length N = 444. 相似文献