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1.
T. S. Evans 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):65-69
Evolving networks with a constant number of edges may be
modelled using a rewiring process. These models are used to
describe many real-world processes including the evolution of
cultural artifacts such as family names, the evolution of gene
variations, and the popularity of strategies in simple
econophysics models such as the minority game. The model is
closely related to Urn models used for glasses, quantum gravity
and wealth distributions. The full mean field equation for the
degree distribution is found and its exact solution and generating
solution are given. 相似文献
2.
W. Q. Duan 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(2):271-276
Identifying universal patterns in complex economic
systems can reveal the dynamics and organizing principles underlying the
process of system evolution. We investigate the scaling behaviours that have
emerged in the international trade system by describing them as a series of
evolving weighted trade networks. The maximum-flow spanning trees (constructed by maximizing the total
weight of the edges) of these networks exhibit two universal scaling
exponents: (1) topological scaling exponent η = 1.30 and (2) flow
scaling exponent ζ = 1.03. 相似文献
3.
M. Gligor M. Ausloos 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):533-539
GDP/capita correlations are investigated in various time windows (TW), for the time interval 1990–2005. The target group of
countries is the set of 25 EU members, 15 till 2004 plus the 10 countries which joined EU later on. The TW-means of the statistical
correlation coefficients are taken as the weights (links) of a fully connected network having the countries as nodes. Thereafter
we define and introduce the overlapping index of weighted network nodes. A cluster structure of EU countries is derived from the statistically relevant eigenvalues and
eigenvectors of the adjacency matrix. This may be considered to yield some information about the structure, stability and
evolution of the EU country clusters in a macroeconomic sense. 相似文献
4.
G. Ghoshal M. E.J. Newman 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):175-184
We consider distributed networks, such as peer-to-peer networks, whose
structure can be manipulated by adjusting the rules by which vertices
enter and leave the network. We focus in particular on degree
distributions and show that, with some mild constraints, it is possible
by a suitable choice of rules to arrange for the network to have any
degree distribution we desire. We also describe a mechanism based on
biased random walks by which appropriate rules could be implemented in
practice. As an example application, we describe and simulate the
construction of a peer-to-peer network optimized to minimize search times
and bandwidth requirements. 相似文献
5.
M. N. Kuperman S. Risau-Gusman 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(2):233-238
In this work we present an analysis of a spatially non homogeneous
ultimatum game. By considering different underlying topologies as
substrates on top of which the game takes place we obtain
nontrivial behaviors for the evolution of the strategies of the
players. We analyze separately the effect of the size of the
neighborhood and the spatial structure. Whereas this last effect
is the most significant one, we show that even for disordered
networks and provided the neighborhood of each site is small, the
results can be significantly different from those obtained in the
case of fully connected networks. 相似文献
6.
V. Zlatic G. Bianconi A. Díaz-Guilera D. Garlaschelli F. Rao G. Caldarelli 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(3):271-275
For many complex networks present in nature only a single instance, usually of large size, is available. Any measurement made
on this single instance cannot be repeated on different realizations. In order to detect significant patterns in a real-world
network it is therefore crucial to compare the measured results with a null model counterpart. Here we focus on dense and
weighted networks, proposing a suitable null model and studying the behaviour of the degree correlations as measured by the
rich-club coefficient. Our method solves an existing problem with the randomization of dense unweighted graphs, and at the
same time represents a generalization of the rich-club coefficient to weighted networks which is complementary to other recently
proposed ones. 相似文献
7.
D. Q. Wei X. S. Luo Y. L. Zou 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):279-282
We investigate how firing activity of complex neural
networks depends on the random long-range connections and coupling
strength. Network elements are described by excitable
space-clamped FitzHugh-Nagumo (SCFHN) neurons with the values of
parameters at which no firing activity occurs. It is found that
for a given appropriate coupling strength C, there exists a
critical fraction of random connections (or randomness) p*,
such that if p > p* the firing neurons, which are absent in the
nearest-neighbor network, occur. The firing activity becomes
more frequent as randomness p is
further increased. On the other hand, when the p is smaller,
there are no active neurons in network, no matter what the value
of C is. For a given larger p, there exist optimal coupling
strength levels, where firing activity reaches its maximum. To the
best of our knowledge, this is a novel mechanism for the emergence
of firing activity in neurons. 相似文献
8.
E. P. Borges D. O. Cajueiro R. F.S. Andrade 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):469-474
The objective of this study is to design a procedure to
characterize chaotic dynamical systems, in which they are
mapped onto a complex network. The nodes represent the regions of space
visited by the system, while the edges represent the transitions between
these regions. Parameters developed to quantify the properties of complex
networks, including those related to higher order neighbourhoods, are used
in the analysis. The methodology is tested on the logistic map, focusing
on the onset of chaos and chaotic regimes. The corresponding networks were
found to have distinct features that are associated with the particular
type of dynamics that generated them. 相似文献
9.
B. Karrer G. Ghoshal 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(2):239-245
There has been a considerable amount of interest in recent years on the robustness of networks to failures. Many previous
studies have concentrated on the effects of node and edge removals on the connectivity structure of a static network; the networks are considered to be static in the sense that no compensatory measures are allowed for recovery of
the original structure. Real world networks such as the world wide web, however, are not static and experience a considerable
amount of turnover, where nodes and edges are both added and deleted. Considering degree-based node removals, we examine the
possibility of preserving networks from these types of disruptions. We recover the original degree distribution by allowing
the network to react to the attack by introducing new nodes and attaching their edges via specially tailored schemes. We focus
particularly on the case of non-uniform failures, a subject that has received little attention in the context of evolving
networks. Using a combination of analytical techniques and numerical simulations, we demonstrate how to preserve the exact degree distribution of the studied networks from various forms of attack. 相似文献
10.
R. F.S. Andrade J. G.V. Miranda S. T.R. Pinho T. P. Lobão 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):247-256
A concept of higher order neighborhood in complex networks,
introduced previously [Phys. Rev. E 73, 046101 (2006)], is systematically
explored to investigate larger scale structures in complex networks. The
basic idea is to consider each higher order neighborhood as a network in
itself, represented by a corresponding adjacency matrix, and to settle a
plenty of new parameters in order to obtain a best characterization of the
whole network. Usual network indices are then used to evaluate the
properties of each neighborhood. The identification of high order
neighborhoods is also regarded as intermediary step towards the evaluation
of global network properties, like the diameter, average shortest path
between node, and network fractal dimension. Results for a large number of
typical networks are presented and discussed. 相似文献
11.
Z.-G. Huang X.-J. Xu Z.-X. Wu Y.-H. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):549-553
We carry out comparative studies of random walks on deterministic
Apollonian networks (DANs) and random Apollonian networks (RANs).
We perform computer simulations for the mean first-passage time,
the average return time, the mean-square displacement, and the
network coverage for the unrestricted random walk. The diffusions
both on DANs and RANs are proved to be sublinear. The effects of
the network structure on the dynamics and the search efficiencies
of walks with various strategies are also discussed. Contrary to
intuition, it is shown that the self-avoiding random walk, which
has been verified as an optimal local search strategy in networks,
is not the best strategy for the DANs in the large size limit. 相似文献
12.
F. Nisbach M. Kaiser 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):185-191
Many networks extent in space, may it be metric (e.g. geographic) or non-metric (ordinal). Spatial network growth, which depends
on the distance between nodes, can generate a wide range of topologies from small-world to linear scale-free networks. However,
networks often lacked multiple clusters or communities. Multiple clusters can be generated, however, if there are time windows
during development. Time windows ensure that regions of the network develop connections at different points in time. This
novel approach could generate small-world but not scale-free networks. The resulting topology depended critically on the overlap
of time windows as well as on the position of pioneer nodes. 相似文献
13.
J. M. Kumpula J. Saramäki K. Kaski J. Kertész 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):41-45
According to Fortunato and Barthélemy, modularity-based community detection
algorithms have a resolution threshold such that small communities in a large
network are invisible. Here we generalize their work and show that the q-state
Potts community detection method introduced by Reichardt and Bornholdt
also has a resolution threshold. The model contains a parameter by which this threshold can be tuned, but no a priori principle
is known to select the proper value.
Single global optimization criteria do not seem capable for detecting all
communities if their size distribution is broad. 相似文献
14.
C. Fretter B. Drossel 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):365-371
We evaluate the probability that a Boolean network returns to an
attractor after perturbing h nodes. We find that the return
probability as function of h can display a variety of different
behaviours, which yields insights into the state-space structure. In
addition to performing computer simulations, we derive analytical
results for several types of Boolean networks, in particular for
Random Boolean Networks. We also apply our method to networks that have
been evolved for robustness to small perturbations, and to a biological example. 相似文献
15.
S. Alfarano T. Lux F. Wagner 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(2):183-187
The present paper expands on recent attempts at
estimating the parameters of simple interacting-agent models of
financial markets [S. Alfarano, T. Lux, F. Wagner, Computational Economics 26, 19 (2005); S. Alfarano, T. Lux, F. Wagner, in Funktionsf?higkeit und
Stabilit?t von Finanzm?rkten, edited by W. Franz, H. Ramser,
M. Stadler (Mohr Siebeck, Tübingen, 2005), pp. 241–254]. Here we
provide additional evidence by (i) investigating a large sample of
individual stocks from the Tokyo Stock Exchange, and (ii)
comparing results from the baseline noise trader/fundamentalist
model of [S. Alfarano, T. Lux, F. Wagner, Computational Economics 26, 19 (2005)] with those obtained from an even
simpler version with a preponderance of noise trader behaviour. As
it turns out, this somewhat more parsimonious “maximally skewed”
variant is often not rejected in favor of the more complex
version. We also find that all stocks are dominated by noise
trader behaviour irrespective of whether the data prefer the
skewed or the baseline version of our model. 相似文献
16.
M. B. Gordon J. R. Iglesias V. Semeshenko J. P. Nadal 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(1):133-144
Crime is an economically relevant activity. It may represent a mechanism of wealth distribution but also a social and economic
burden because of the interference with regular legal activities and the cost of the law enforcement system. Sometimes it
may be less costly for the society to allow for some level of criminality. However, a drawback of such a policy is that it
may lead to a high increase of criminal activity, that may become hard to reduce later on. Here we investigate the level of
law enforcement required to keep crime within acceptable limits. A sharp phase transition is observed as a function of the
probability of punishment. We also analyze other consequences of criminality as the growth of the economy, the inequality
in the wealth distribution (the Gini coefficient) and other relevant quantities under different scenarios of criminal activity
and probabilities of apprehension. 相似文献
17.
M. N. Kuperman M. Ballard F. Laguna 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):513-520
A model for a dynamic network consisting of changing
local interactions is presented in this work. While the network
maintains solely local connections, certain properties known only
to Small World Networks may be extracted due to the dynamic nature
of the model. At each time step the individuals are grouped into
clusters creating neighborhoods or domains of fully connected
agents. The boundaries of these domains change in time,
corresponding to a situation where the links between individuals
are dynamic only throughout the history of the network. A question
that we pose is whether our model, which maintains a local
structure such that diffusion calculations are possible, might
lead to analytic or conceptual advances for the much more
complicated case of diffusion on a static disordered network that
exhibits the same macroscopic properties as our dynamic
ordered network. To answer this, we compare certain properties
which characterize the dynamic domain network to those of a Small
World Network, and then analyze the diffusion coefficients for
three possible domain mutations. We close with a comparison and
confirmation of previous epidemiological work carried out on
networks. 相似文献
18.
S. Drożdż A. Z. Górski J. Kwapień 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):499-502
World currency network constitutes one of the most complex structures that
is associated with the contemporary civilization. On a way towards
quantifying its characteristics we study the
cross correlations in changes of the daily foreign exchange rates within
the basket of 60 currencies in the period December 1998–May 2005. Such
a dynamics turns out to predominantly involve one outstanding eigenvalue
of the correlation matrix. The magnitude of this eigenvalue depends however
crucially on which currency is used as a base currency for the remaining ones.
Most prominent it looks from the perspective of a peripheral currency.
This largest eigenvalue is seen to systematically decrease and thus
the structure of correlations becomes more heterogeneous,
when more significant currencies are used as reference.
An extreme case in this later respect is the USD in the period considered.
Besides providing further insight into subtle nature of complexity,
these observations point to a formal procedure that in general
can be used for practical purposes of measuring the relative
currencies significance on various time horizons. 相似文献
19.
E. A. Leicht G. Clarkson K. Shedden M. E.J. Newman 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):75-83
In this paper we examine a number of methods for probing and
understanding the large-scale structure of networks that evolve over
time. We focus in particular on citation networks, networks of
references between documents such as papers, patents, or court cases. We
describe three different methods of analysis, one based on an
expectation-maximization algorithm, one based on modularity optimization,
and one based on eigenvector centrality. Using the network of citations
between opinions of the United States Supreme Court as an example, we
demonstrate how each of these methods can reveal significant structural
divisions in the network and how, ultimately, the combination of all
three can help us develop a coherent overall picture of the network's
shape. 相似文献
20.
A. P. Quayle A. S. Siddiqui S. J.M. Jones 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(4):617-630
We propose a model of an underlying mechanism responsible for the formation of assortative mixing in networks between “similar”
nodes or vertices based on generic vertex properties. Existing models focus on a particular type of assortative mixing, such
as mixing by vertex degree, or present methods of generating a network with certain properties, rather than modeling a mechanism
driving assortative mixing during network growth. The motivation is to model assortative mixing by non-topological vertex
properties, and the influence of these non-topological properties on network topology. The model is studied in detail for
discrete and hierarchical vertex properties, and we use simulations to study the topology of resulting networks. We show that
assortative mixing by generic properties directly drives the formation of community structure beyond a threshold assortativity
of r ∼0.5, which in turn influences other topological properties. This direct relationship is demonstrated by introducing
a new measure to characterise the correlation between assortative mixing and community structure in a network. Additionally,
we introduce a novel type of assortative mixing in systems with hierarchical vertex properties, from which a hierarchical
community structure is found to result.
Electronic supplementary material Supplementary Online Material 相似文献