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951.
H.K. Janssen U.C. Täuber E. Frey 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):491-511
We investigate the Kardar-Parisi-Zhang (KPZ) equation in d spatial dimensions with Gaussian spatially long-range correlated noise -- characterized by its second moment -- by means of dynamic field theory and the renormalization group. Using a stochastic Cole-Hopf transformation we derive
exact exponents and scaling functions for the roughening transition and the smooth phase above the lower critical dimension . Below the lower critical dimension, there is a line marking the stability boundary between the short-range and long-range noise fixed points. For , the general structure of the renormalization-group equations fixes the values of the dynamic and roughness exponents exactly,
whereas above , one has to rely on some perturbational techniques. We discuss the location of this stability boundary in light of the exact results derived in this paper, and from results known in the literature. In particular, we conjecture
that there might be two qualitatively different strong-coupling phases above and below the lower critical dimension, respectively.
Received 5 August 1998 相似文献
952.
The asymptotic distribution of some test criteria for a covariance matrix are derived under local alternatives. Except for the existence of some higher moments, no assumption as to the form of the distribution function is made. As an illustration, a case of t distribution included normal model is considered and the power of the likelihood ratio test and Nagao's test for sphericity, as described in Srivastava and Khatri and Anderson, is computed. Also, the power is computed using the bootstrap method. In the case of t distribution, the bootstrap approximation does not appear to be as good as the one obtained by the asymptotic expansion method. 相似文献
953.
A.A. Tarasenko F. Nieto L. Jastrabík C. Uebing 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):311-322
A two-dimensional lattice-gas model with square symmetry is investigated by using the real-space renormalization group (RSRG)
approach with blocks of different size and symmetries. It has been shown that the precision of the method depends strongly
not only on the number of sites in the block but also on its symmetry. In general, the accuracy of the method increases with
the number of sites in the block. The minimal relative error in determining the critical values of the interaction parameters
is equal to . Using the RSRG method, we have explored phase diagrams of both a two-dimensional Ising spin model and of a square lattice
gas with lateral interactions between adparticles. We also have investigated the influence of the attractive and repulsive
interactions on both the thermodynamic properties of the lattice gas and the diffusion of adsorbed particles over surface.
We have calculated adsorption isotherms and coverage dependences of the pair correlation function, isothermal susceptibility
and the chemical diffusion coefficient. In addition, we have included in our analysis the interaction of the activated particle
in the saddle point with its nearest neighbors. We have also used Monte Carlo (MC) technique to calculate these dependences.
Despite the fact that both methods constitute very different approaches, the correspondence of the numerical data is surprisingly
good. Therefore, we conclude that the RSRG approach can be applied to characterize the thermodynamic and kinetic properties
of systems of particles with strong lateral interactions.
Received 1st September 1998 and Received in final form 8 March 2000 相似文献
954.
E.L. Præstgaard B. Schmittmann R.K.P. Zia 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):675-695
We investigate the collective behavior of an Ising lattice gas, driven to non-equilibrium steady states by being coupled to
two thermal baths. Monte Carlo methods are applied to a two-dimensional system in which one of the baths is fixed at infinite
temperature. Both generic long range correlations in the disordered state and critical properties near the second order transition
are measured. Anisotropic scaling, a key feature near criticality, is used to extract and some critical exponents. On the theoretical front, a continuum theory, in the spirit of Landau-Ginzburg, is presented.
Being a renormalizable theory, its predictions can be computed by standard methods of -expansions and found to be consistent with simulation data. In particular, the critical behavior of this system belongs to
a universality class which is quite different from the uniformly driven Ising model.
Received 4 October 2000 相似文献
955.
We study homogeneous, independent percolation on general quasi-transitive graphs. We prove that in the disorder regime where
all clusters are finite almost surely, in fact the expectation of the cluster size is finite. This extends a well-known theorem
by Menshikov and Aizenman & Barsky to all quasi-transitive graphs. Moreover we deduce that in this disorder regime the cluster
size distribution decays exponentially, extending a result of Aizenman & Newman. Our results apply to both edge and site percolation,
as well as long range (edge) percolation. The proof is based on a modification of the Aizenman & Barsky method. 相似文献
956.
957.
We investigate the sample-to-sample fluctuations in the conductivity of a random resistor network—equivalently, in the diffusivity of a disordered medium with symmetric hopping rates. We argue that whenever the effective conductivity
* is strictly positive, then the fluctuations are normal, i.e., proportional to (volume)–1/2. If the local conductivities are allowed to be zero, then
* vanishes when approaching the percolation thresholdp
c. Close top
c the fluctuations are anomalous. From the renormalization group on hierarchical lattices we find that atp
c fluctuations and mean scale in the same fashion, i.e., there is no independent scaling exponent for the fluctuations. 相似文献
958.
Bootstrap方法在回归分析上的应用 总被引:1,自引:0,他引:1
陈红 《新疆大学学报(理工版)》1999,16(3):50-52
本文用Bootstrap方法,给出了对一般回归模型参数的最小二乘估计的特征的估计的计算机模拟工应用于实际问题中,得到了较好的结果。 相似文献
959.
N. S. Branco 《Journal of statistical physics》1993,70(3-4):1035-1044
In bootstrap percolation, sites are occupied with probabilityp, but those with less thanm occupied first neighbors are removed. This culling process is repeated until a stable configuration (all occupied sites have at leastm occupied first neighbors or the whole lattice is empty) is achieved. Formm
1 the transition is first order, while form<m
1 it is second order, withm-dependent exponents. In probabilistic bootstrap percolation, sites have probabilityr or (1–r) of beingm- orm-sites, respectively (m-sites are those which need at leastm occupied first neighbors to remain occupied). We have studied the model on Bethe lattices, where an exact solution is available. Form=2 andm=3, the transition changes from second to first order atr
1=1/2, and the exponent is different forr<1/2,r=1/2, andr>1/2. The same qualitative behavior is found form=1 andm=3. On the other hand, form=1 andm=2 the transition is always second order, with the same exponents ofm=1, for any value ofr>0. We found, form=z–1 andm=z, wherez is the coordination number of the lattice, thatp
c=1 for a value ofr which depends onz, but is always above zero. Finally, we argue that, for bootstrap percolation on real lattices, the exponents and form=2 andm=1 are equal, for dimensions below 6.On leave from Universidade Federal de Santa Catarina, Depto. de Fisica, 88049, Florianópolis, SC, Brazil 相似文献
960.
We numerically investigate the electric potential distribution over a two-dimensional continuum percolation model between the electrodes. The model consists of overlapped conductive particles on the background with an infinitesimal conductivity. Using the finite difference method, we solve the generalized Laplace equation and show that in the potential distribution, there appear quasi-equipotential clusters which approximately and locally have the same values as steps and stairs. Since the quasi-equipotential clusters have the fractal structure, we compute the fractal dimension of equipotential curves and its dependence on the volume fraction over [0,1]. The fractal dimension in [1.00, 1.246] has a peak at the percolation threshold pc. 相似文献