共查询到20条相似文献,搜索用时 31 毫秒
1.
X.S. Chen V. Dohm 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):687-703
We reexamine the range of validity of finite-size scaling in the lattice model and the field theory below four dimensions. We show that general renormalization-group arguments based on the renormalizability of
the theory do not rule out the possibility of a violation of finite-size scaling due to a finite lattice constant and a finite
cutoff. For a confined geometry of linear size L with periodic boundary conditions we analyze the approach towards bulk critical behavior as at fixed for where is the bulk correlation length. We show that for this analysis ordinary renormalized perturbation theory is sufficient. On
the basis of one-loop results and of exact results in the spherical limit we find that finite-size scaling is violated for
both the lattice model and the field theory in the region . The non-scaling effects in the field theory and in the lattice model differ significantly from each other.
Received 5 February 1999 相似文献
2.
3.
H. Chamati D.M. Danchev N.S. Tonchev 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):307-316
A d-dimensional quantum model system confined to a general hypercubical geometry with linear spatial size L and “temporal size” 1/T ( T - temperature of the system) is considered in the spherical approximation under periodic boundary conditions. For a film
geometry in different space dimensions , where is a parameter controlling the decay of the long-range interaction, the free energy and the Casimir amplitudes are given.
We have proven that, if , the Casimir amplitude of the model, characterizing the leading temperature corrections to its ground state, is . The last implies that the universal constant of the model remains the same for both short, as well as long-range interactions, if one takes the normalization factor for
the Gaussian model to be such that . This is a generalization to the case of long-range interaction of the well-known result due to Sachdev. That constant differs
from the corresponding one characterizing the leading finite-size corrections at zero temperature which for is .
Received 3 June 1999 and Received in final form 16 August 1999 相似文献
4.
I.L. Menezes-Sobrinho J.G. Moreira A.T. Bernardes 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):313-318
We study the existence of distinct failure regimes in a model for fracture in fibrous materials. We simulate a bundle of parallel
fibers under uniaxial static load and observe two different failure regimes: a catastrophic and a slowly shredding. In the
catastrophic regime the initial deformation produces a crack which percolates through the bundle. In the slowly shredding
regime the initial deformations will produce small cracks which gradually weaken the bundle. The boundary between the catastrophic
and the shredding regimes is studied by means of percolation theory and of finite-size scaling theory. In this boundary, the
percolation density scales with the system size L, which implies the existence of a second-order phase transition with the same critical exponents as those of usual percolation.
Received 24 June 1999 相似文献
5.
X.S. Chen V. Dohm D. Stauffer 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):699-704
Using field theory and Monte Carlo (MC) simulation we investigate the finite-size effects of the magnetization M for the three-dimensional Ising model in a finite cubic geometry with periodic boundary conditions. The field theory with
infinite cutoff gives a scaling form of the equation of state where is the reduced temperature, h is the external field and L is the size of system. Below and at the theory predicts a nonmonotonic dependence of f(x,y) with respect to at fixed and a crossover from nonmonotonic to monotonic behaviour when y is further increased. These results are confirmed by MC simulation. The scaling function f(x,y) obtained from the field theory is in good quantitative agreement with the finite-size MC data. Good agreement is also found
for the bulk value at .
Received 20 July 1999 and Received in final form 11 November 1999 相似文献
6.
A.K. Hartmann U. Nowak 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(1):105-109
We investigate the critical behavior of three-dimensional random-field Ising systems with both Gauss and bimodal distribution
of random fields and additional the three-dimensional diluted Ising antiferromagnet in an external field. These models are
expected to be in the same universality class. We use exact ground-state calculations with an integer optimization algorithm
and by a finite-size scaling analysis we calculate the critical exponents , , and . While the random-field model with Gauss distribution of random fields and the diluted antiferromagnet appear to be in same
universality class, the critical exponents of the random-field model with bimodal distribution of random fields seem to be
significantly different.
Received: 9 July 1998 / Received in final form: 15 July 1998 / Accepted: 20 July
1998 相似文献
7.
E. Carlon M. Henkel U. Schollwöck 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):99-114
The density matrix renormalization group ( DMRG) is applied to some one-dimensional reaction-diffusion models in the vicinity
of and at their critical point. The stochastic time evolution for these models is given in terms of a non-symmetric “quantum
Hamiltonian”, which is diagonalized using the DMRG method for open chains of moderate lengths (up to about 60 sites). The
numerical diagonalization methods for non-symmetric matrices are reviewed. Different choices for an appropriate density matrix
in the non-symmetric DMRG are discussed. Accurate estimates of the steady-state critical points and exponents can then be
found from finite-size scaling through standard finite-lattice extrapolation methods. This is exemplified by studying the
leading relaxation time and the density profiles of diffusion-annihilation and of a branching-fusing model in the directed
percolation universality class.
Received 2 February 1999 相似文献
8.
J.P. Kemp U.H.E. Hansmann Zheng Yu Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(2):371-374
The similarity in the thermodynamic properties of two completely different theoretical models for the helix-coil transition
is examined critically. The first model is an all-atomic representation for a poly-alanine chain, while the second model is
a minimal helix-forming model that contains no system specifics. Key characteristics of the helix-coil transition, in particular,
the effective critical exponents of these two models agree with each other, within a finite-size scaling analysis.
Received 8 December 1999 相似文献
9.
M. Bengrine A. Benyoussef A. El Kenz M. Loulidi F. Mhirech 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):129-133
A one-dimensional model of a rice-pile is numerically studied for different driving mechanisms. We found that for a sufficiently
large system, there is a sharp transition between the trivial behaviour of a 1D BTW model and self-organized critical (SOC)
behaviour. Depending on the driving mechanism, the self-organized critical rice-pile model belongs to two different universality
classes.
Received 18 December 1998 相似文献
10.
Anomalous scaling in the Zhang model 总被引:2,自引:0,他引:2
R. Pastor-Satorras A. Vespignani 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):197-200
We apply the moment analysis technique to analyze large scale simulations of the Zhang sandpile model. We find that this model
shows different scaling behavior depending on the update mechanism used. With the standard parallel updating, the Zhang model
violates the finite-size scaling hypothesis, and it also appears to be incompatible with the more general multifractal scaling
form. This makes impossible its affiliation to any one of the known universality classes of sandpile models. With sequential
updating, it shows scaling for the size and area distribution. The introduction of stochasticity into the toppling rules of
the parallel Zhang model leads to a scaling behavior compatible with the Manna universality class.
Received 8 August 2000 and Received in final form 4 October 2000 相似文献
11.
V. N. Kondratyev Ph. Blanchard H. O. Lutz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):241-244
The multi-fragmentation dynamics of noble gas atomic clusters is considered for different statistically distributed deposited
energies. The conditions giving rise to the development of criticality in the cluster evolution are revealed from an analysis
of the signals in the fragment mass distribution. The time dependence of the observables related to critical exponents is
studied. It is demonstrated that in a certain regime the cluster exhibits a behavior which can be identified as the precursor
of a second-order liquid-gas phase transition.
Received 1st September 1998 and Received in final form 14 January 1999 相似文献
12.
B. Dubrulle 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):757-771
We develop a new approach to scale symmetry, which takes into account the possible finite cut-offs of the fields or the parameters.
This new symmetry, called finite size scale symmetry: i) includes the traditional self-similarity as a limiting case, when
the cut-offs are set to infinity (infinite size-system); ii) is consistent with the traditional finite size scaling approach
already used in critical phenomena; iii) enables the computation of some of the universal functions appearing in the finite
size scaling formulation; iv) allows scale transformations leaving the cut-offs invariant, like in the traditional renormalization
approach; v) can be formulated to allow for positive or negative fields and parameters; vi) leads to new predictions about
the shape of some distributions in critical phenomena or turbulence which are in very good agreement with the experimental
or numerical findings.
Received 26 January 1999 and Received in final form 25 October 1999 相似文献
13.
M.C. Marques J.F.F. Mendes 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):123-127
We propose and study a model where two aspects are present: parity conservation and infinitely many absorbing states. Whereas
steady-state simulations show that the static critical behaviour is not affected by the presence of multiple absorbing configurations,
the influence of the initial state associated with the presence of slowly decaying memory effects is clearly displayed in
time dependent simulations. We report results of a detailed investigation of the dependence of critical spreading exponents
on the initial particle density.
Received 13 January 1999 and Received in final form 7 April 1999 相似文献
14.
Y. Chen S.H. Guo Z.B. Li S. Marculescu L. Schülke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):289-296
The renormalisation group approach is applied to the study of the short-time critical behaviour of the d-dimensional Ginzburg-Landau model with long-range interaction of the form in momentum space. Firstly the system is quenched from a high temperature to the critical temperature and then relaxes to
equilibrium within the model A dynamics. The asymptotic scaling laws and the initial slip exponents and of the order parameter and the response function respectively, are calculated to the second order in .
Received 9 June 2000 and Received in final form 2 August 2000 相似文献
15.
The dynamics of intermittent granular flow through an orifice at the bottom of a granular bin and the associated clogging
due to formation of arches blocking the outlet, is studied numerically in two dimensions. When the hole size is less than
the grain diameter, only a single grain is removed from the system so that the system self-organizes to a steady state and
the distribution of the grain displacements decays as power laws. On the other hand, when hole sizes are within few times
of the grain diameter, the outflow distributions are also observed to follow a power law.
Received 21 July 1999 and Received in final form 17 September 1999 相似文献
16.
X.S. Chen V. Dohm 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):529-542
We derive exact results for several thermodynamic quantities of the O
(
n
) symmetric field theory in the limit in a finite d-dimensional hypercubic geometry with periodic boundary conditions. Corresponding results are derived for an O
(
n
) symmetric model on a finite d-dimensional lattice with a finite-range interaction. The leading finite-size effects near Tc of the field-theoretic model are compared with those of the lattice model. For 2 <
d
< 4, the finite-size scaling functions are verified to be universal. For d
> 4, significant lattice effects are found. Finite-size scaling in its usual simple form does not hold for d
> 4 but remains valid in a generalized form with two reference lengths. The finite-size scaling functions of the field theory turn out to be nonuniversal whereas those of the lattice model are independent of the nonuniversal model parameters. In particular, the field-theoretic model exhibits finite-size
effects whose leading exponents differ from those of the lattice model. The widely accepted lowest-mode approach is shown
to fail for both the field-theoretic and the lattice model above four dimensions.
Received: 20 October 1997 / Accepted: 5 March 1998 相似文献
17.
S.A. Hassan A.R. Vasconcellos R. Luzzi 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):131-139
We analyze in detail the nonlinear kinetics of a carrier system in a photoinjected plasma in semiconductors under the action
of constant illumination with ultraviolet light. We show that the spatially homogeneous steady-state becomes unstable, and
a charge density wave emerges after a critical intensity of the incident radiation is achieved. It is shown that this instability
can only follow in doped p-type materials. In bulk systems the critical intensity was found to be too high making the phenomenon not observable under
realistic experimental conditions. However, a more efficient electron excitation can be obtained in low dimensional p-type systems, like some molecular and biological polymers, where the interaction may follow by chemical interaction with
the medium. We show that for intensities beyond the critical threshold an increasing number of modes provide further contributions
(subharmonics) to the space inhomogeneity. It is conjectured that this process could lead the system to display chaotic-like
behavior.
Received 8 July 1998 and Received in final form 6 May 1999 相似文献
18.
J.P. Vishwakarma 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):369-372
The variation of flow-variables with distance, in the flow-field behind a shock wave propagating in a dusty gas with exponentially
varying density, are obtained at different times. The equilibrium flow conditions are assumed to be maintained, and the results
are compared with those obtained for a perfect gas. It is found that the presence of small solid particles in the medium has
significant effects on the variation of density and pressure.
Received 20 October 1999 and Received in final form 9 March 2000 相似文献
19.
F. Hontinfinde S. Bekhechi R. Ferrando 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):681-686
We have studied by means of Monte-Carlo simulation and exact finite-size analysis, the spin-1 Blume Capel model with Glauber
and Kawasaki dynamics. The Kawasaki spin-exchange process transfers energy into the system from an external source. Some phase
diagrams of the model are presented. For some parameter values, the system displays a kind of self-organization phenomenon
within the disordered phase.
Received 15 February 2000 相似文献
20.
R.G. da Silva M.L. Lyra C.R. da Silva G.M. Viswanathan 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):693-697
In this work, we introduce a restricted ballistic deposition model with symmetric growth rules that favors the formation of
local finite slopes. It is the simplest model which, even without including a diffusive relaxation mode of the interface,
leads to a macroscopic groove instability. By employing a finite-size scaling of numerical simulation data, we determine the
scaling behavior of the surface structure grown over a one-dimensional substrate of linear size L. We found that the surface profile develops a macroscopic groove with the asymptotic surface width scaling as , with . The early-time dynamics is governed by the scaling law , with . We further investigate the sensitivity to initial conditions of the present model by applying damage spreading techniques.
We find that the early-time distance between two initially close surface configurations grows in a ballistic fashion as , but a slower Brownian-like scaling () sets up for evolution times much larger than a characteristic time scale .
Received 26 May 2000 相似文献