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31.
K.J. Wiese M. Kardar 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(2):187-190
We introduce a generalization of the O(N) field theory to N-colored membranes of arbitrary inner dimension D. The O(N) model is obtained for , while leads to self-avoiding tethered membranes (as the O(N) model reduces to self-avoiding polymers). The model is studied perturbatively by a 1-loop renormalization group analysis,
and exactly as .Freedom to choose the expansion point D, leads to precise estimates of critical exponents of the O(N) model. Insights gained from this generalization include a conjecture on the nature of droplets dominating the 3d-Ising model at criticality; and the fixed point governing the random bond Ising model.
Received: 15 October 1998 / Accepted: 4 November 1998 相似文献
32.
D. Daboul I. Chang A. Aharony 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):303-316
We study the site and bond quantum percolation model on the two-dimensional square lattice using series expansion in the low
concentration limit. We calculate series for the averages of , where T
ij
(E) is the transmission coefficient between sites i and j, for k=0, 1, , 5 and for several values of the energy E near the center of the band. In the bond case the series are of order p14 in the concentration p(some of those have been formerly available to order p10) and in the site case of order p16. The analysis, using the Dlog-Padé approximation and the techniques known as M1 and M2, shows clear evidence for a delocalization
transition (from exponentially localized to extended or power-law-decaying states) at an energy-dependent threshold p
q(E) in the range , confirming previous results (e.g.
and for bond and site percolation) but in contrast with the Anderson model. The divergence of the series for different kis characterized by a constant gap exponent, which is identified as the localization length exponent from a general scaling assumption. We obtain estimates of . These values violate the bound of Chayes et al.
Received 28 February 2000 相似文献
33.
M. Schulze S. Gourley S. A. Brown A. Dunbar J. Partridge R. J. Blaikie 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):291-294
A range of percolating atomic cluster films, with
nanoscale overall dimensions, have been studied using a
combination of in situ and
ex situ electrical transport
measurements, together with field emission electron microscopy
and atomic force microscopy. Bismuth clusters with mean diameter
20 nm were deposited between electrical contacts defined by
electron beam lithography. The morphology of the films can be
understood within percolation theory, and the electrical
measurements show complex behaviour characteristic of both
percolation effects and modification of the cluster films by
current flow and by oxidation. 相似文献
34.
F. Iglói D. Karevski H. Rieger 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):613-625
We consider cooperative processes (quantum spin chains and random walks) in one-dimensional fluctuating random and aperiodic
environments characterized by fluctuating exponents . At the critical point the random and aperiodic systems scale essentially anisotropically in a similar fashion: length (L) and time (t) scales are related as . Also some critical exponents, characterizing the singularities of average quantities, are found to be universal functions
of , whereas some others do depend on details of the distribution of the disorder. In the off-critical region there is an important
difference between the two types of environments: in aperiodic systems there are no extra (Griffiths)-singularities.
Received: 5 February 1998 / Accepted: 17 April 1998 相似文献
35.
On the genre-fication of music: a percolation approach 总被引:1,自引:0,他引:1
R. Lambiotte M. Ausloos 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):183-188
We analyze web-downloaded data on
people
sharing their music library. By attributing to each music group usual music genres (Rock, Pop ...),
and analysing correlations between music groups of different genres with percolation-idea based methods,
we probe the reality of these subdivisions and construct a music genre cartography, with a tree representation. We also discuss
an alternative objective way to classify music, that is based on the complex structure of the groups audience. Finally, a
link is drawn with the theory of hidden variables in complex networks. 相似文献
36.
A. D.F. Dunbar J. G. Partridge M. Schulze S. A. Brown 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):415-422
Nano-particles of Bi, Ag and Sb have been produced in an inert gas
aggregation source and deposited between lithographically defined electrical
contacts on SiN. The morphology of these films have been examined by atomic
force microscopy and scanning electron microscopy. The Bi nano-particles
stick well to the SiN substrate and take on a flattened dome shape. The Ag
nano-particles also stick well to the SiN surface; however they retain a
more spherical shape. Whereas, many of the Sb nano-particles bounce off the
SiN surface with only a small fraction of the Sb nano-particles aggregating
at defects resulting in a non-random distribution of the clusters. These
nano-scale differences in the film morphology influence the viability of
applying percolation theory to in situ macroscopic measurements of the film
conductivity, during the deposition process. For Bi and Ag nano-particles the
increase in conductivity follows a power law. The power law exponent, t, was
found to be 1.27 ±0.13 and 1.40 ±0.14, for Bi and Ag
respectively, in agreement with theoretical predictions of t ≈1.3
for 2D random continuum percolation networks. Sb cluster networks do not
follow this model and due to the majority of the Sb clusters bouncing off
the surface. Differences in the current onset times and final conductance
values of the films are also discussed. 相似文献
37.
L. Turban 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):331-338
Shape-dependent universal crossing probabilities are studied, via Monte Carlo simulations, for bond and site directed percolation on the square lattice in the diagonal direction, at the percolation
threshold. In a dynamical interpretation, the crossing probability is the probability that, on a system with size L, an epidemic spreading without immunization remains active at time t. Since the system is strongly anisotropic, the shape dependence in space-time enters through the effective aspect ratio r
eff = ct/L
z, where c is a non-universal constant and z the anisotropy exponent. A particular attention is paid to the influence of the initial state on the universal behaviour
of the crossing probability. Using anisotropic finite-size scaling and generalizing a simple argument given by Aizenman for
isotropic percolation, we also obtain the behaviour of the probability to find n incipient spanning clusters on a finite system at time t. The numerical results are in good agreement with the conjecture.
Received 10 February 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: turban@lpm.u-nancy.fr
RID="b"
ID="b"UMR CNRS 7556 相似文献
38.
H. Chamati 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):241-249
The finite-size critical properties of the (n) vector ϕ4 model, with long-range interaction decaying algebraically with the interparticle distance r like r
-d - σ, are investigated. The system is confined to a finite geometry subject to periodic boundary condition. Special attention
is paid to the finite-size correction to the bulk susceptibility above the critical temperature T
c. We show that this correction has a power-law nature in the case of pure long-range interaction i.e. 0 < σ < 2 and it turns out to be exponential in case of short-range interaction i.e.σ = 2. The results are valid for arbitrary dimension d, between the lower ( d
< = σ) and the upper ( d
> = 2σ) critical dimensions.
Received 2 July 2001 and Received in final form 4 Septembre 2001 相似文献
39.
C.B. Yang X. Cai 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):375-379
A new type of spatio-temporal correlation function for the process approaching the self-organized criticality is investigated
within the Bak-Sneppen model for biological evolution. In terms of the “directional shorter distance” between the two sites
with minimum fitness at two successive updates, the correlation function is defined and studied numerically for the nearest-
and random-neighbor versions of the model. Qualitatively different behaviors of the jump of the minimal site in the two models
are presented, and the behaviors of the correlation functions are shown also different.
Received 14 April 2001 and Received in final form 28 June 2001 相似文献
40.
H. Hinrichsen M. Howard 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):635-643
We introduce a model for the spreading of epidemics by long-range infections and investigate the critical behaviour at the
spreading transition. The model generalizes directed bond percolation and is characterized by a probability distribution for
long-range infections which decays in d spatial dimensions as . Extensive numerical simulations are performed in order to determine the density exponent and the correlation length exponents and for various values of . We observe that these exponents vary continuously with , in agreement with recent field-theoretic predictions. We also study a model for pairwise annihilation of particles with
algebraically distributed long-range interactions.
Received: 4 September 1998 / Accepted: 22 September 1998 相似文献