17,017 research outputs found
Update rules and interevent time distributions: Slow ordering vs. no ordering in the Voter Model
We introduce a general methodology of update rules accounting for arbitrary
interevent time distributions in simulations of interacting agents. In
particular we consider update rules that depend on the state of the agent, so
that the update becomes part of the dynamical model. As an illustration we
consider the voter model in fully-connected, random and scale free networks
with an update probability inversely proportional to the persistence, that is,
the time since the last event. We find that in the thermodynamic limit, at
variance with standard updates, the system orders slowly. The approach to the
absorbing state is characterized by a power law decay of the density of
interfaces, observing that the mean time to reach the absorbing state might be
not well defined.Comment: 5pages, 4 figure
Fronts, Domain Growth and Dynamical Scaling in a d=1 non-Potential System
We present a study of dynamical scaling and front motion in a one dimensional
system that describes Rayleigh-Benard convection in a rotating cell. We use a
model of three competing modes proposed by Busse and Heikes to which spatial
dependent terms have been added. As long as the angular velocity is different
from zero, there is no known Lyapunov potential for the dynamics of the system.
As a consequence the system follows a non-relaxational dynamics and the
asymptotic state can not be associated with a final equilibrium state. When the
rotation angular velocity is greater than some critical value, the system
undergoes the Kuppers-Lortz instability leading to a time dependent chaotic
dynamics and there is no coarsening beyond this instability. We have focused on
the transient dynamics below this instability, where the dynamics is still
non-relaxational. In this regime the dynamics is governed by a non-relaxational
motion of fronts separating dynamically equivalent homogeneous states. We
classify the families of fronts that occur in the dynamics, and calculate their
shape and velocity. We have found that a scaling description of the coarsening
process is still valid as in the potential case. The growth law is nearly
logarithmic with time for short times and becomes linear after a crossover,
whose width is determined by the strength of the non-potential terms.Comment: 15 pages, 10 figure
A Parallel Branch and Bound Algorithm for the Maximum Labelled Clique Problem
The maximum labelled clique problem is a variant of the maximum clique
problem where edges in the graph are given labels, and we are not allowed to
use more than a certain number of distinct labels in a solution. We introduce a
new branch-and-bound algorithm for the problem, and explain how it may be
parallelised. We evaluate an implementation on a set of benchmark instances,
and show that it is consistently faster than previously published results,
sometimes by four or five orders of magnitude.Comment: Author-final version. Accepted to Optimization Letter
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
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
The Economic and Social Impact of Tourism
This paper analyzes the economic and social impact of tourism in Pagsanjan in which tourism development project is located. Results show that the project’s various significant impacts include increases in employment and income and stimulation of political and women’s participation. While its impact on environment and on the people’s social life has been a mixture of positive and negative results, its impact on income distribution has been trifling. To maximize the tourism multiplier, the paper encourages the collaboration of the tourism project with other programs devised to boost the capacity of the local economy. Tourism manpower training agenda should include training for women skills while tourism promotions should move from sex-oriented markets to prevent several disorientations in the cultural values of the tourism industries.tourism
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