421 research outputs found
Evolution of Cooperative Networks and the Emergence of Leadership
A generic property of biological, social and economical networks is their ability to evolve in time, creating or supressing links. We model this situation with an adaptive network of agents playing a Prisoner's Dilemma game. Each agent plays with its local neighbors, collects an aggregate payoff and imitates the strategy of its best neighbor. Furthermore we allow the agents adapt their local neighborhood according to their satisfaction level and the strategy played. Therefore each agent will have diverse environments that induces an interesting dynamics in the cooperation fraction of the whole network. In the absence of noise, a steady state is always reached, where the strategies and the neighborhoods remain stationary, and where for a wide range of parameter values, an almost full cooperative outcome is obtained. The topology of the network in these states reveals that cooperators with a large number of connections emerges. These "leaders" are shown to be very important in understanding the global stability of the final steady state. If the "leaders" are perturbated, then global cascades arise and the system oscillates between the nearly full defection network and the fully cooperative outcome, before settling again in a nearly fully cooperative outcome.Cooperation -- Evolutionary Game Theory -- Stochastic Networks -- Prisoner Dilemma
Absorbing and Shattered Fragmentation Transitions in Multilayer Coevolution
We introduce a coevolution voter model in a multilayer, by coupling a
fraction of nodes across two network layers and allowing each layer to evolve
according to its own topological temporal scale. When these time scales are the
same the dynamics preserve the absorbing-fragmentation transition observed in a
monolayer network at a critical value of the temporal scale that depends on
interlayer connectivity. The time evolution equations obtained by pair
approximation can be mapped to a coevolution voter model in a single layer with
an effective average degree. When the two layers have different topological
time scales we find an anomalous transition, named shattered fragmentation, in
which the network in one layer splits into two large components in opposite
states and a multiplicity of isolated nodes. We identify the growth of the
number of components as a signature of this anomalous transition. We also find
a critical level of interlayer coupling needed to prevent the fragmentation in
a layer connected to a layer that does not fragment.Comment: 7 pages, 6 figures, last figure caption includes link to animation
Noise in Coevolving Networks
Coupling dynamics of the states of the nodes of a network to the dynamics of
the network topology leads to generic absorbing and fragmentation transitions.
The coevolving voter model is a typical system that exhibits such transitions
at some critical rewiring. We study the robustness of these transitions under
two distinct ways of introducing noise. Noise affecting all the nodes destroys
the absorbing-fragmentation transition, giving rise in finite-size systems to
two regimes: bimodal magnetisation and dynamic fragmentation. Noise Targeting a
fraction of nodes preserves the transitions but introduces shattered
fragmentation with its characteristic fraction of isolated nodes and one or two
giant components. Both the lack of absorbing state for homogenous noise and the
shift in the absorbing transition to higher rewiring for targeted noise are
supported by analytical approximations.Comment: 20 page
Data-driven modeling of systemic delay propagation under severe meteorological conditions
The upsetting consequences of weather conditions are well known to any person
involved in air transportation. Still the quantification of how these
disturbances affect delay propagation and the effectiveness of managers and
pilots interventions to prevent possible large-scale system failures needs
further attention. In this work, we employ an agent-based data-driven model
developed using real flight performance registers for the entire US airport
network and focus on the events occurring on October 27 2010 in the United
States. A major storm complex that was later called the 2010 Superstorm took
place that day. Our model correctly reproduces the evolution of the
delay-spreading dynamics. By considering different intervention measures, we
can even improve the model predictions getting closer to the real delay data.
Our model can thus be of help to managers as a tool to assess different
intervention measures in order to diminish the impact of disruptive conditions
in the air transport system.Comment: 9 pages, 5 figures. Tenth USA/Europe Air Traffic Management Research
and Development Seminar (ATM2013
Divergent Time Scale in Axelrod Model Dynamics
We study the evolution of the Axelrod model for cultural diversity. We
consider a simple version of the model in which each individual is
characterized by two features, each of which can assume q possibilities. Within
a mean-field description, we find a transition at a critical value q_c between
an active state of diversity and a frozen state. For q just below q_c, the
density of active links between interaction partners is non-monotonic in time
and the asymptotic approach to the steady state is controlled by a time scale
that diverges as (q-q_c)^{-1/2}.Comment: 4 pages, 5 figures, 2-column revtex4 forma
Microscopic Abrams-Strogatz model of language competition
The differential equations of Abrams and Strogatz for the competition between
two languages are compared with agent-based Monte Carlo simulations for fully
connected networks as well as for lattices in one, two and three dimensions,
with up to 10^9 agents.Comment: 10 pages, 7 figure
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