127 research outputs found
Fluctuations in network dynamics
Most complex networks serve as conduits for various dynamical processes,
ranging from mass transfer by chemical reactions in the cell to packet transfer
on the Internet. We collected data on the time dependent activity of five
natural and technological networks, finding that for each the coupling of the
flux fluctuations with the total flux on individual nodes obeys a unique
scaling law. We show that the observed scaling can explain the competition
between the system's internal collective dynamics and changes in the external
environment, allowing us to predict the relevant scaling exponents.Comment: 4 pages, 4 figures. Published versio
First-order transition in small-world networks
The small-world transition is a first-order transition at zero density of
shortcuts, whereby the normalized shortest-path distance undergoes a
discontinuity in the thermodynamic limit. On finite systems the apparent
transition is shifted by . Equivalently a ``persistence
size'' can be defined in connection with finite-size
effects. Assuming , simple rescaling arguments imply that
. We confirm this result by extensive numerical simulation in one to
four dimensions, and argue that implies that this transition is
first-order.Comment: 4 pages, 3 figures, To appear in Europhysics Letter
Emergence of Clusters in Growing Networks with Aging
We study numerically a model of nonequilibrium networks where nodes and links
are added at each time step with aging of nodes and connectivity- and
age-dependent attachment of links. By varying the effects of age in the
attachment probability we find, with numerical simulations and scaling
arguments, that a giant cluster emerges at a first-order critical point and
that the problem is in the universality class of one dimensional percolation.
This transition is followed by a change in the giant cluster's topology from
tree-like to quasi-linear, as inferred from measurements of the average
shortest-path length, which scales logarithmically with system size in one
phase and linearly in the other.Comment: 8 pages, 6 figures, accepted for publication in JSTA
Using Entropy-Based Methods to Study General Constrained Parameter Optimization Problems
In this letter we propose the use of physics techniques for entropy
determination on constrained parameter optimization problems. The main feature
of such techniques, the construction of an unbiased walk on energy space,
suggests their use on the quest for optimal solutions of an optimization
problem. Moreover, the entropy, and its associated density of states, give us
information concerning the feasibility of solutions.Comment: 10 pages, 3 figures, references correcte
Morphogenèse et soulèvement de la Cordillère orientale des Andes de Bolivie au Cénozoïque
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