摘要:

AbstractThe collisional broadening and shift of four spectral lines of neon (747.2, 748.8, 753.5, 754.4 nm) arising from 2p53p‐ 2p53d transitions, emitted from a low‐pressure glow discharge in pure neon and neon‐helium mixtures have been measured using a Fabry‐Perot interferometer. The values of pressure broadening and shift coefficients are determined and analyzed in terms of the impact

ISSN:0003-3804    

DOI:10.1002/andp.19935050102

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractTwo‐dimensional hydrodynamic calculations for a self‐gravitating, magnetic and compressible medium are carried out. The results based on numerical simulations show that the joint effect of the nonlinearity of the hydrodynamic equations and self‐gravity is the mechanism for generating the observed complex structure of molecular clouds (e.g. clumps and filaments). In addition, parameters such as the evolution time of molecular clouds, the density contrast, fractal dimension, and the velocity probability distribution are derived. Their possible relation to the observed properties of molecular clouds are disc

ISSN:0003-3804    

DOI:10.1002/andp.19935050103

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA calculation is carried out of the effect of imposed inertial forces on the critical dynamics of a pure fluid near the liquid‐vapor critical point. The mechanism for the relaxation of the critical fluctuations of the order parameter is the Brownian motion in the long wavelength hydrodynamic shear modes. The additional fluctuating inertial forces add noise to these modes, leading to an increase inγq, the order parameter relaxation rate for a fluctuation of wave numberq. A general formula is derived for Δγq/γq, the fractional increase in relaxation rate, in terms of the acceleration power spectral density. The predicted strong dependences on temperature, angle, andqprovide crucial tests for the t

ISSN:0003-3804    

DOI:10.1002/andp.19935050104

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe one‐dimensional Hubbard model with different on‐site interaction on the even (Ua) and odd (Ub) sites is considered within the framework of the weak coupling approach. In the case of a 1/4‐filled band the dynamical nonequivalence of sites leads to the appearance of Umklapp processes in the system and to the dynamical generation of a commensurability gap in the charge excitation spectrum forUa≠UbandUa>0 orUb>0. Depending on the relation between the bare coupling constants the system shows four different regimes of behaviour in the infrared limit corresponding to normal metal, nonmagnetic insulator, antiferromagnetic insulator and superconducting states. The extended model including interaction between particles on nearest and next‐nearest neighbour sites is also c

ISSN:0003-3804    

DOI:10.1002/andp.19935050105

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractWe review the nonlinear σ‐model approach to the localization problem. However, different from usual, we do not make use of replicas or superfields in order to perform the averaging over the realizations of the disorder. Instead, we pursue the derivation of the nonlinear σ‐model as an effective theory for the disordered electron system within the framework of the so‐called time‐path formalism, which is a real‐time finite‐temperature quantum field theory. This formalism is especially suitable for the description of the disordered electron system due to the automatic normalization of real‐time quantities, thereby avoiding the denominator problem. We shall compare this dynamic method with the replica‐ and superfield‐methods as the perturbative level of the calculation of

ISSN:0003-3804    

DOI:10.1002/andp.19935050106

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractWe consider two‐dimensional Ising models bounded by general parabolic curves and study their transfer matrices and associated quantum spin chains. We derive their eigenvalue spectra numerically and analytically, both at the critical point and in its vicinity. From this we find how the geometrical form of the system is reflected in the spectrum and how it influences the critical behaviour near the ti

ISSN:0003-3804    

DOI:10.1002/andp.19935050107

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractWe present a Monte Carlo simulation algorithm for evaluating the stationary probability and the mean and the variance of first passage times in any dynamical system under the influence of additive coloured Gaussian and Marcovian noise (Ornstein‐Uhlenbeck process). Our algorithm generates the Ornstein‐Uhlenbeck process by a superposition of a finite number of random telegraph processes. We obtain our results from a direct evaluation of the trajectories. We apply our method to the overdamped motion of a particle in a double well potential. We compare our simulation results with various analytic approximations for the stationary probability and the mean first passage ti

ISSN:0003-3804    

DOI:10.1002/andp.19935050108

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractSimulations in lattices of size 1003at the critical point of the three‐dimensional Glauber kinetic Ising model indicate that the 1935 Becker‐Doring equation no longer works there: The growth rates decay in time. These conclusions confirm those in two dimensi

ISSN:0003-3804    

DOI:10.1002/andp.19935050109

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

ISSN:0003-3804    

DOI:10.1002/andp.19935050101

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY