共查询到20条相似文献,搜索用时 15 毫秒
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A. Garber H. Kantz 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(3):437-443
The BTW Abelian sandpile model is a prominent example of systems showing self-organised criticality (SOC) in the infinite
size limit. We study finite-size effects with special focus on the statistics of extreme events, i.e., of particularly large
avalanches. Not only the avalanche size probability distribution, but also the mutual independence of large avalanches in
the critical state is affected by finite-size effects. Instead of a Poissonian recurrencetime distribution, in the finite
system we find a repulsion of extreme events that depends on the avalanche size and not on the respective probability. The
dependence of these effects on the system size is investigated and some data collapse is found. Our results imply that SOC
is an unsuitable mechanism for the explanation of extreme events which occur in clusters. 相似文献
3.
A. H. Rodríguez H. Y. Ramírez 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):235-238
With the help of metadynamics it is possible to calculate efficiently the free energy of systems displaying high energy barriers
as a function of few selected “collective variables”. In doing this, the contribution of all the other degrees of freedom
(“microscopic” variables) is averaged out and, thus, lost. In the following it is shown that it is possible to calculate the
thermal average of these microscopic degrees of freedom during the metadynamics, not loosing this piece of information. The
method is tested on a two-dimensional toy system and on a small molecule, that is dialanine. 相似文献
4.
C. J. Tessone R. Toral 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,71(4):549-555
We perform a computational study of a variant of the “train” model for earthquakes [Phys. Rev. A 46, 6288 (1992)], where we assume a static friction that is a stochastic function of position rather than being velocity dependent.
The model consists of an array of blocks coupled by springs, with the forces between neighbouring blocks balanced by static
friction. We calculate the probability, P(s), of the occurrence of avalanches with a size s or greater, finding that our results
are consistent with the phenomenology and also with previous models which exhibit a power law over a wide range. We show that
the train model may be mapped onto a stochastic sandpile model and study a variant of the latter for non-spherical grains.
We show that, in this case, the model has critical behaviour only for grains with large aspect ratio, as was already shown
in experiments with real ricepiles. We also demonstrate a way to introduce randomness in a physically motivated manner into
the model. 相似文献
5.
K. Christensen N. Farid G. Pruessner M. Stapleton 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):331-336
We derive general properties of the finite-size scaling of
probability density functions and show that when the apparent
exponent
of a probability density is less than 1, the
associated finite-size scaling ansatz has a scaling exponent τ
equal to 1, provided that the fraction of events in the universal
scaling part of the probability density function is non-vanishing in
the thermodynamic limit.
We find the general result that τ≥1 and
.
Moreover, we show that if the scaling function
approaches a
non-zero constant for small arguments,
, then
.
However, if the scaling function vanishes for small arguments,
, then τ= 1, again assuming a
non-vanishing fraction of universal events.
Finally, we apply the formalism developed to examples from the literature,
including some where misunderstandings of the theory of scaling have led to erroneous conclusions. 相似文献
6.
R. Grammauta D. Molteni G. Basilone C. Guisande A. Bonanno S. Aronica G. Giacalone I. Fontana M. Zora B. Patti A. Cuttitta G. Buscaino R. Sorgente S. Mazzola 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):459-467
The physical and chemical processes of the sea greatly affect the reproductive biology of fishes, mainly influencing both
the numbers of spawned eggs and the survivorship of early stages up to the recruitment period. In the central Mediterranean,
the European anchovy constitutes one of the most important fishery resource. Because of its short living nature and of its
recruitment variability, associated to high environmental variability, this small pelagic species undergo high interannual
fluctuation in the biomass levels. Despite several efforts were addressed to characterize fishes spawning habitat from the
oceanographic point of view, very few studies analyze the air-sea exchanges effects. To characterize the spawning habitat
of these resources a specific technique (quotient rule analysis) was applied on air-sea heat fluxes, wind stress, sea surface
temperature and turbulence data, collected in three oceanographic surveys during the summer period of 2004, 2005 and 2006.
The results showed the existence of preferred values in the examined physical variables, associated to anchovy spawning areas.
Namely, for heat fluxes the values were around −40 W/m2, for wind stress 0.04–0.11 N/m2, for SST 23°C, and 300 − 500 m3s−3 for wind mixing. Despite the obtained results are preliminary, this is the first relevant analysis on the air-sea exchanges
and their relationship with the fish biology of pelagic species. 相似文献
7.
L. Gauvin J. Vannimenus J.-P. Nadal 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(2):293-304
The collective behavior in a variant of Schelling’s segregation model is characterized with methods borrowed from statistical
physics, in a context where their relevance was not conspicuous. A measure of segregation based on cluster geometry is defined
and several quantities analogous to those used to describe physical lattice models at equilibrium are introduced. This physical
approach allows to distinguish quantitatively several regimes and to characterize the transitions between them, leading to
the building of a phase diagram. Some of the transitions evoke empirical sudden ethnic turnovers. We also establish links
with ‘spin-1’ models in physics. Our approach provides generic tools to analyze the dynamics of other socio-economic systems. 相似文献
8.
A. A. Bukharov A. S. Ovchinnikov N. V. Baranov K. Inoue 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(3):369-375
We use agent-based modeling to investigate the effect of conservatism and partisanship on the efficiency with which large
populations solve the density classification task – a paradigmatic problem for information aggregation and consensus building.
We find that conservative agents enhance the populations’ ability to efficiently solve the density classification task despite
large levels of noise in the system. In contrast, we find that the presence of even a small fraction of partisans holding
the minority position will result in deadlock or a consensus on an incorrect answer. Our results provide a possible explanation
for the emergence of conservatism and suggest that even low levels of partisanship can lead to significant social costs.
Electronic supplementary material Supplementary Online Material 相似文献
9.
J. D. Noh 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):251-257
We study a scaling property of the number Mh(N) of loops of size h in
complex networks with respect to a network size N.
For networks with a bounded second moment of degree,
we find two distinct scaling behaviors:
Mh(N) ~ (constant) and
Mh(N) ~ lnN as N increases.
Uncorrelated random networks specified only with a degree distribution
and Markovian networks specified only with a nearest neighbor
degree-degree correlation display the former scaling behavior, while
growing network models display the latter.
The difference is attributed
to structural correlation that cannot be captured by a short-range
degree-degree correlation. 相似文献
10.
G. Yan Z.-Q. Fu G. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(4):591-594
We study the SIS epidemic dynamics on scale-freeweighted networks with asymmetric infection, by both analysis andnumerical
simulations, with focus on the epidemic threshold aswell as critical behaviors. It is demonstrated that the asymmetryof infection
plays an important role: we could redistribute theasymmetry to balance the degree heterogeneity of the network andthen to
restore the epidemic threshold to a fnite value. On theother hand, we show that the absence of the epidemic threshold isnot
so bad as commented previously since the prevalence grows veryslowly in this case and one could only protect a few vertices
toprevent the diseases propagation. 相似文献
11.
L. Tian D.-N. Shi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(2):167-171
In this paper, we study a rank-based model for weighted network. The evolution rule of the network is based on the ranking
of node strength, which couples the topological growth and the weight dynamics. Analytically and by simulations, we demonstrate
that the generated networks recover the scale-free distributions of degree and strength in the whole region of the growth
dynamics parameter (α>0). Moreover, this network evolution mechanism can also produce scale-free property of weight, which
adds deeper comprehension of the networks growth in the presence of incomplete information. We also characterize the clustering
and correlation properties of this class of networks. It is showed that at α=1 a structural phase transition occurs, and for
α>1 the generated network simultaneously exhibits hierarchical organization and disassortative degree correlation, which is
consistent with a wide range of biological networks. 相似文献
12.
C. Sire S. Redner 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(3):473-481
The European Physical Journal B - Can one understand the statistics of wins and losses of baseball teams? Are their consecutive-game winning and losing streaks self-reinforcing or can they be... 相似文献
13.
G. Yan Z. -Q. Fu G. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):515-520
We study the consensus dynamics with or without time-delays on directed and undirected de Bruijn graphs. Our results show
that consensus on an undirected de Bruijn graph has a lower converging speed and larger time-delay tolerance in comparison
with that on an undirected scale-free network. Although there is not much difference between the eigenvalue ratios of the
two undirected networks, we found that their dynamical properties are remarkably different; consequently, it is seemingly
more informative to consider the second smallest and the largest eigenvalues separately rather than considering their ratio
in the study of synchronization of a coupled oscillators network. Moreover, our study on directed de Bruijn graphs reveals
that properly setting directions on edges can improve the converging speed and time-delay tolerance simultaneously. 相似文献
14.
E. Olbrich N. Bertschinger N. Ay J. Jost 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(3):407-415
We study how statistical complexity depends on the system size and how the
complexity of the whole system relates to the complexity of its subsystems.
We study this size dependence for two well-known complexity measures, the
excess entropy of Grassberger and the neural complexity introduced by Tononi, Sporns and Edelman. We compare these results
to properties of complexity measures that one might wish to impose when seeking an axiomatic characterization. It turns out
that those two measures do not satisfy all those requirements, but a renormalized version of the TSE-complexity behaves reasonably
well. 相似文献
15.
A. H. Darooneh B. Rahmani 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(2):287-291
Zipf’s original law deals with the statistics of ranked words in natural languages. It has recently been generalized to “words”
defined as n-tuples of symbols derived by translation of real-valued univariate timeseries into a literal sequence. We verify
that the rank-frequency plot of these words shows, for fractional Brownian motion, the previously found power laws, but with
large finite length corrections. We verify a finite size scaling ansatz for these corrections and, as aresult, demonstrate
greatly improved estimates of the (generalized) Zipf exponents. This allows us to find the correct relation between the Zipf
exponent and the Hurst exponent characterizing the fractional Brownian motion. 相似文献
16.
J. Jekni?-Dugi? 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):193-204
The large molecules lie in the “border territory" between the “quantum" and the “classical". To which extent one should employ
the classical or quantum-mechanical methods in describing their behavior is an open issue. To this end, the problem of the
large-molecules conformational stability and transitions is typical. While the small or medium-size molecules are successfully
described by the quantum mechanical methods, the large-molecules conformational transitions are usually investigated classically.
However, the problem of the origin of stability of the large-molecules conformations remains open. In this paper, we offer
a solution-in-principle for both the large-molecules conformational stability and transitions yet in the context of the quantum
decoherence theory. Actually, we apply the “environment-induced superselection rules" theory that naturally answers both of
the problems, and, in a sense, offers a unifying picture for the molecules in a solution. Generality of our approach stems
from the generality of the decoherence theory. So, our approach is a qualitative theoretical program alternating the point
of view to the large-molecules dynamics: while ultimately being the quantum-mechanical systems, the large molecules in a solution
may still exhibit the (approximately) classical behavior of their conformational degrees of freedom. 相似文献
17.
Self-organized Monte Carlo simulations are suggested. Their essence is artificial dynamics consisting of the well-known single-spin-flip
Metropolis algorithm supplemented by biased random walk in temperature space. The action of walker is driven by feedback utilizing
the linear filtering recursion based on the instantaneous estimates of Binder cumulants. The simulation for 2d Ising model
demonstrates that the mean temperature typical for the steady noncanonical equilibrium regime properly approximates the true
critical temperature. The estimates of the critical Binder cumulants and critical exponents are also discussed. 相似文献
18.
W. X. Wang B. Y. Lin C. L. Tang G. R. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):529-536
We propose a Finite-Memory Naming Game (FMNG) model with
respect to the bounded rationality of agents or finite resources for
information storage in communication systems. We study its dynamics
on several kinds of complex networks, including random networks,
small-world networks and scale-free networks. We focus on the
dynamics of the FMNG affected by the memory restriction as well as
the topological properties of the networks. Interestingly, we found
that the most important quantity, the convergence time of reaching
the consensus, shows some non-monotonic behaviors by varying the
average degrees of the networks with the existence of the fastest
convergence at some specific average degrees. We also investigate
other main quantities, such as the success rate in negotiation, the
total number of words in the system and the correlations between
agents of full memory and the total number of words, which clearly
explain the nontrivial behaviors of the convergence. We provide some
analytical results which help better understand the dynamics of the
FMNG. We finally report a robust scaling property of the convergence
time, which is regardless of the network structure and the memory
restriction. 相似文献
19.
A. Barra L. DeSanctis 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(1):119-124
In this paper we analyze two main prototypes of disordered mean-field systems, namely the Sherrington-Kirkpatrick (SK) and
the Viana-Bray (VB) models, to show that, in the framework of the cavity method, the transition from the annealed regime to
a broken replica symmetry phase can be thought of as the failure of the saturability property (detailed explained along the paper) of the overlap fluctuations which act as the order parameters of the theory.
We show furthermore how this coincides with the lacking of the commutativity of the infinite volume limit with respect to
a, suitably chosen, vanishing perturbing field inducing the transition as prescribed by standard statistical mechanics. This
is another step towards a complete theory of disordered systems. As a well known consequence it turns out that the annealed
and the replica symmetric regions must coincide, implying that the averaged overlap is zero in this phase. Within our framework
the finding of the values of the critical point for the SK and line for the VB becomes available straightforwardly and the
method is of a large generality and applicable to several other mean field models 相似文献
20.
L. Wu S. Zhu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(1):87-93
Load-dependent random walks are used to investigate the evolution of
load distribution in transportation network systems. The walkers hop
to a node according to node load of the last time step. The
preference of walks leads to a change in the load distribution. It
changes from degree-dependent distribution in the case of
non-preference walks to eigenvector-centrality-dependent
distribution. By numerical simulations, it is shown that the network
heterogeneity has a influence on the effect of walk preference. In
the cascading failure phenomenon, an appropriate degree correlation
can guarantee a low risk of cascading failures. 相似文献