1,216 research outputs found
Percolation transition and distribution of connected components in generalized random network ensembles
In this work, we study the percolation transition and large deviation
properties of generalized canonical network ensembles. This new type of random
networks might have a very rich complex structure, including high heterogeneous
degree sequences, non-trivial community structure or specific spatial
dependence of the link probability for networks embedded in a metric space. We
find the cluster distribution of the networks in these ensembles by mapping the
problem to a fully connected Potts model with heterogeneous couplings. We show
that the nature of the Potts model phase transition, linked to the birth of a
giant component, has a crossover from second to first order when the number of
critical colors in all the networks under study. These results shed
light on the properties of dynamical processes defined on these network
ensembles.Comment: 27 pages, 15 figure
Growing Cayley trees described by Fermi distribution
We introduce a model for growing Cayley trees with thermal noise. The
evolution of these hierarchical networks reduces to the Eden model and the
Invasion Percolation model in the limit , respectively.
We show that the distribution of the bond strengths (energies) is described by
the Fermi statistics. We discuss the relation of the present results with the
scale-free networks described by Bose statistics
Quantum statistics in complex networks
In this work we discuss the symmetric construction of bosonic and fermionic
networks and we present a case of a network showing a mixed quantum statistics.
This model takes into account the different nature of nodes, described by a
random parameter that we call energy, and includes rewiring of the links. The
system described by the mixed statistics is an inhomogemeous system formed by
two class of nodes. In fact there is a threshold energy such that
nodes with lower energy increase their connectivity
while nodes with higher energy decrease their
connectivity in time.Comment: 5 pages, 2 figure
Final state interaction effects in scattering
We present a systematic study of the final-state interaction (FSI) effects in
scattering in the CEBAF energy range with particular emphasis on the
phenomenon of the angular anisotropy of the missing momentum distribution. We
find that FSI effects dominate at missing momentum p_m \gsim 1.5 fm.
FSI effects in the excitation of the -wave state are much stronger than in
the excitation of the -wave.Comment: LATEX, 11 pages, 5 figures available from the authors on request,
KFA-IKP(TH)-1994-3
An extended formalism for preferential attachment in heterogeneous complex networks
In this paper we present a framework for the extension of the preferential
attachment (PA) model to heterogeneous complex networks. We define a class of
heterogeneous PA models, where node properties are described by fixed states in
an arbitrary metric space, and introduce an affinity function that biases the
attachment probabilities of links. We perform an analytical study of the
stationary degree distributions in heterogeneous PA networks. We show that
their degree densities exhibit a richer scaling behavior than their homogeneous
counterparts, and that the power law scaling in the degree distribution is
robust in presence of heterogeneity
Non-neutral theory of biodiversity
We present a non-neutral stochastic model for the dynamics taking place in a
meta-community ecosystems in presence of migration. The model provides a
framework for describing the emergence of multiple ecological scenarios and
behaves in two extreme limits either as the unified neutral theory of
biodiversity or as the Bak-Sneppen model. Interestingly, the model shows a
condensation phase transition where one species becomes the dominant one, the
diversity in the ecosystems is strongly reduced and the ecosystem is
non-stationary. This phase transition extend the principle of competitive
exclusion to open ecosystems and might be relevant for the study of the impact
of invasive species in native ecologies.Comment: 4 pages, 3 figur
Maximal planar scale-free Sierpinski networks with small-world effect and power-law strength-degree correlation
Many real networks share three generic properties: they are scale-free,
display a small-world effect, and show a power-law strength-degree correlation.
In this paper, we propose a type of deterministically growing networks called
Sierpinski networks, which are induced by the famous Sierpinski fractals and
constructed in a simple iterative way. We derive analytical expressions for
degree distribution, strength distribution, clustering coefficient, and
strength-degree correlation, which agree well with the characterizations of
various real-life networks. Moreover, we show that the introduced Sierpinski
networks are maximal planar graphs.Comment: 6 pages, 5 figures, accepted by EP
Final state interactions and correlations: are the latter observable?
Are effects of short range correlations in the ground state of the target
nucleus (initial state correlations ISC) observable in experiments on
quasielastic scattering at large missing momentum ? Will the
missing momentum spectrum observed at CEBAF be overwhelmed by final state
interactions (FSI) of the struck proton? The recent advances in the theory of
FSI and findings of complex interplay and strong quantum-mechanical
interference of FSI and ISC contributions to scattering at p_{m}\gsim
1\,fm are reviewed. We conclude that for p_m \gsim 1 \, fm
quasielastic scattering is dominated by FSI effects and the sensitivity to
details of the nuclear ground state is lost.Comment: Invited Talk given by N.N.Nikolaev at the Conference on Perspectives
in Nuclear Physics at Intermediate Energies (Trieste, Italy, May 1995) 18
pages, uuencoded including all figure
Entropy measures for complex networks: Toward an information theory of complex topologies
The quantification of the complexity of networks is, today, a fundamental
problem in the physics of complex systems. A possible roadmap to solve the
problem is via extending key concepts of information theory to networks. In
this paper we propose how to define the Shannon entropy of a network ensemble
and how it relates to the Gibbs and von Neumann entropies of network ensembles.
The quantities we introduce here will play a crucial role for the formulation
of null models of networks through maximum-entropy arguments and will
contribute to inference problems emerging in the field of complex networks.Comment: (4 pages, 1 figure
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