10,584 research outputs found
A model for cross-cultural reciprocal interactions through mass media
We investigate the problem of cross-cultural interactions through mass media
in a model where two populations of social agents, each with its own internal
dynamics, get information about each other through reciprocal global
interactions. As the agent dynamics, we employ Axelrod's model for social
influence. The global interaction fields correspond to the statistical mode of
the states of the agents and represent mass media messages on the cultural
trend originating in each population. Several phases are found in the
collective behavior of either population depending on parameter values: two
homogeneous phases, one having the state of the global field acting on that
population, and the other consisting of a state different from that reached by
the applied global field; and a disordered phase. In addition, the system
displays nontrivial effects: (i) the emergence of a largest minority group of
appreciable size sharing a state different from that of the applied global
field; (ii) the appearance of localized ordered states for some values of
parameters when the entire system is observed, consisting of one population in
a homogeneous state and the other in a disordered state. This last situation
can be considered as a social analogue to a chimera state arising in globally
coupled populations of oscillators.Comment: 8 pages and 7 figure
Dynamics of link states in complex networks: The case of a majority rule
Motivated by the idea that some characteristics are specific to the relations
between individuals and not of the individuals themselves, we study a prototype
model for the dynamics of the states of the links in a fixed network of
interacting units. Each link in the network can be in one of two equivalent
states. A majority link-dynamics rule is implemented, so that in each dynamical
step the state of a randomly chosen link is updated to the state of the
majority of neighboring links. Nodes can be characterized by a link
heterogeneity index, giving a measure of the likelihood of a node to have a
link in one of the two states. We consider this link-dynamics model on fully
connected networks, square lattices and Erd \"os-Renyi random networks. In each
case we find and characterize a number of nontrivial asymptotic configurations,
as well as some of the mechanisms leading to them and the time evolution of the
link heterogeneity index distribution. For a fully connected network and random
networks there is a broad distribution of possible asymptotic configurations.
Most asymptotic configurations that result from link-dynamics have no
counterpart under traditional node dynamics in the same topologies.Comment: 9 pages, 13 figure
Dynamics of the Formation of Bright Solitary Waves of Bose-Einstein Condensates in Optical Lattices
We present a detailed description of the formation of bright solitary waves
in optical lattices. To this end, we have considered a ring lattice geometry
with large radius. In this case, the ring shape does not have a relevant effect
in the local dynamics of the condensate, while offering a realistic set up to
implement experiments with conditions usually not available with linear
lattices (in particular, to study collisions). Our numerical results suggest
that the condensate radiation is the relevant dissipative process in the
relaxation towards a self-trapped solution. We show that the source of
dissipation can be attributed to the presence of higher order dispersion terms
in the effective mass approach. In addition, we demonstrate that the stability
of the solitary solutions is linked with particular values of the width of the
wavepacket in the reciprocal space. Our study suggests that these critical
widths for stability depend on the geometry of the energy band, but are
independent of the condensate parameters (momentum, atom number, etc.).
Finally, the non-solitonic nature of the solitary waves is evidenced showing
their instability under collisions.Comment: 7 pages, 7 figures, to appear in PR
Time scale competition leading to fragmentation and recombination transitions in the coevolution of network and states
We study the co-evolution of network structure and node states in a model of
multiple state interacting agents. The system displays two transitions, network
recombination and fragmentation, governed by time scales that emerge from the
dynamics. The recombination transition separates a frozen configuration,
composed by disconnected network components whose agents share the same state,
from an active configuration, with a fraction of links that are continuously
being rewired. The nature of this transition is explained analytically as the
maximum of a characteristic time. The fragmentation transition, that appears
between two absorbing frozen phases, is an anomalous order-disorder transition,
governed by a crossover between the time scales that control the structure and
state dynamics.Comment: 5 pages, 5 figures, figures 2 and 4 changed, tile changed, to be
published in PR
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
Conservation laws for the voter model in complex networks
We consider the voter model dynamics in random networks with an arbitrary
distribution of the degree of the nodes. We find that for the usual node-update
dynamics the average magnetization is not conserved, while an average
magnetization weighted by the degree of the node is conserved. However, for a
link-update dynamics the average magnetization is still conserved. For the
particular case of a Barabasi-Albert scale-free network the voter model
dynamics leads to a partially ordered metastable state with a finite size
survival time. This characteristic time scales linearly with system size only
when the updating rule respects the conservation law of the average
magnetization. This scaling identifies a universal or generic property of the
voter model dynamics associated with the conservation law of the magnetization.Comment: 5 pages, 4 figures; for related material please visit
http://www.imedea.uib.e
Information feedback and mass media effects in cultural dynamics
We study the effects of different forms of information feedback associated
with mass media on an agent-agent based model of the dynamics of cultural
dissemination. In addition to some processes previously considered, we also
examine a model of local mass media influence in cultural dynamics. Two
mechanisms of information feedback are investigated: (i) direct mass media
influence, where local or global mass media act as an additional element in the
network of interactions of each agent, and (ii) indirect mass media influence,
where global media acts as a filter of the influence of the existing network of
interactions of each agent. Our results generalize previous findings showing
that cultural diversity builds-up by increasing the strength of the mass media
influence. We find that this occurs independently of the mechanisms of action
(direct or indirect) of the mass media message. However, through an analysis of
the full range of parameters measuring cultural diversity, we establish that
the enhancement of cultural diversity produced by interaction with mass media
only occurs for strong enough mass media messages. In comparison with previous
studies a main different result is that weak mass media messages, in
combination with agent-agent interaction, are efficient in producing cultural
homogeneity. Moreover, the homogenizing effect of weak mass media messages are
more efficient for direct local mass media messages than for global mass media
messages or indirect global mass media influences.Comment: 20n pages, 10 figure
Scaling in the structure of directory trees in a computer cluster
We describe the topological structure and the underlying organization
principles of the directories created by users of a computer cluster when
storing his/her own files. We analyze degree distributions, average distance
between files, distribution of communities and allometric scaling exponents of
the directory trees. We find that users create trees with a broad, scale-free
degree distribution. The structure of the directories is well captured by a
growth model with a single parameter. The degree distribution of the different
trees has a non-universal exponent associated with different values of the
parameter of the model. However, the distribution of community sizes has a
universal exponent analytically obtained from our model.Comment: refined data analysis and modeling, completely reorganized version, 4
pages, 2 figure
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