3,933 research outputs found
Fragmentation transition in a coevolving network with link-state dynamics
We study a network model that couples the dynamics of link states with the
evolution of the network topology. The state of each link, either A or B, is
updated according to the majority rule or zero-temperature Glauber dynamics, in
which links adopt the state of the majority of their neighboring links in the
network. Additionally, a link that is in a local minority is rewired to a
randomly chosen node. While large systems evolving under the majority rule
alone always fall into disordered topological traps composed by frustrated
links, any amount of rewiring is able to drive the network to complete order,
by relinking frustrated links and so releasing the system from traps. However,
depending on the relative rate of the majority rule and the rewiring processes,
the system evolves towards different ordered absorbing configurations: either a
one-component network with all links in the same state or a network fragmented
in two components with opposite states. For low rewiring rates and finite size
networks there is a domain of bistability between fragmented and non-fragmented
final states. Finite size scaling indicates that fragmentation is the only
possible scenario for large systems and any nonzero rate of rewiring.Comment: 10 pages, 13 figure
Temporal disorder in up-down symmetric systems
The effect of temporal disorder on systems with up-down Z2 symmetry is
studied. In particular, we analyze two well-known families of phase
transitions: the Ising and the generalized voter universality classes, and
scrutinize the consequences of placing them under fluctuating global
conditions. We observe that variability of the control parameter induces in
both classes "Temporal Griffiths Phases" (TGP). These recently-uncovered phases
are analogous to standard Griffiths Phases appearing in systems with quenched
spatial disorder, but where the roles of space and time are exchanged. TGPs are
characterized by broad regions in parameter space in which (i) mean
first-passage times scale algebraically with system size, and (ii) the system
response (e.g. susceptibility) diverges. Our results confirm that TGPs are
quite robust and ubiquitous in the presence of temporal disorder. Possible
applications of our results to examples in ecology are discussed
The Impact of Social Curiosity on Information Spreading on Networks
Most information spreading models consider that all individuals are identical
psychologically. They ignore, for instance, the curiosity level of people,
which may indicate that they can be influenced to seek for information given
their interest. For example, the game Pok\'emon GO spread rapidly because of
the aroused curiosity among users. This paper proposes an information
propagation model considering the curiosity level of each individual, which is
a dynamical parameter that evolves over time. We evaluate the efficiency of our
model in contrast to traditional information propagation models, like SIR or
IC, and perform analysis on different types of artificial and real-world
networks, like Google+, Facebook, and the United States roads map. We present a
mean-field approach that reproduces with a good accuracy the evolution of
macroscopic quantities, such as the density of stiflers, for the system's
behavior with the curiosity. We also obtain an analytical solution of the
mean-field equations that allows to predicts a transition from a phase where
the information remains confined to a small number of users to a phase where it
spreads over a large fraction of the population. The results indicate that the
curiosity increases the information spreading in all networks as compared with
the spreading without curiosity, and that this increase is larger in spatial
networks than in social networks. When the curiosity is taken into account, the
maximum number of informed individuals is reached close to the transition
point. Since curious people are more open to a new product, concepts, and
ideas, this is an important factor to be considered in propagation modeling.
Our results contribute to the understanding of the interplay between diffusion
process and dynamical heterogeneous transmission in social networks.Comment: 8 pages, 5 figure
Rescue of endemic states in interconnected networks with adaptive coupling
We study the Susceptible-Infected-Susceptible model of epidemic spreading on two layers of networks interconnected by adaptive links, which are rewired at random to avoid contacts between infected and susceptible nodes at the interlayer. We find that the rewiring reduces the effective connectivity for the transmission of the disease between layers, and may even totally decouple the networks. Weak endemic states, in which the epidemics spreads when the two layers are interconnected but not in each layer separately, show a transition from the endemic to the healthy phase when the rewiring overcomes a threshold value that depends on the infection rate, the strength of the coupling and the mean connectivity of the networks. In the strong endemic scenario, in which the epidemics is able to spread on each separate network -and therefore on the interconnected system- the prevalence in each layer decreases when increasing the rewiring, arriving to single network values only in the limit of infinitely fast rewiring. We also find that rewiring amplifies finite-size effects, preventing the disease transmission between finite networks, as there is a non zero probability that the epidemics stays confined in only one network during its lifetime.Instituto de Física de Líquidos y Sistemas Biológico
Epidemics and chaotic synchronization in recombining monogamous populations
We analyze the critical transitions (a) to endemic states in an SIS
epidemiological model, and (b) to full synchronization in an ensemble of
coupled chaotic maps, on networks where, at any given time, each node is
connected to just one neighbour. In these "monogamous" populations, the lack of
connectivity in the instantaneous interaction pattern -that would prevent both
the propagation of an infection and the collective entrainment into
synchronization- is compensated by occasional random reconnections which
recombine interacting couples by exchanging their partners. The transitions to
endemic states and to synchronization are recovered if the recombination rate
is sufficiently large, thus giving rise to a bifurcation as this rate varies.
We study this new critical phenomenon both analytically and numerically
Multistate voter model with imperfect copying
The voter model with multiple states has found applications in areas as diverse as population genetics, opinion formation, species competition, and language dynamics, among others. In a single step of the dynamics, an individual chosen at random copies the state of a random neighbor in the population. In this basic formulation, it is assumed that the copying is perfect, and thus an exact copy of an individual is generated at each time step. Here, we introduce and study a variant of the multistate voter model in mean field that incorporates a degree of imperfection or error in the copying process, which leaves the states of the two interacting individuals similar but not exactly equal. This dynamics can also be interpreted as a perfect copying with the addition of noise: a minimalistic model for flocking. We found that the ordering properties of this multistate noisy voter model, measured by a parameter ψ in [0,1], depend on the amplitude η of the copying error or noise and the population size N . In the case of perfect copying η = 0 , the system reaches an absorbing configuration with complete order ( ψ = 1 ) for all values of N . However, for any degree of imperfection η > 0 , we show that the average value of ψ at the stationary state decreases with N as ⟨ ψ ⟩ ≃ 6 / ( π 2 η 2 N ) for η ≪ 1 and η 2 N ≳ 1 , and thus the system becomes totally disordered in the thermodynamic limit N → ∞ . We also show that ⟨ ψ ⟩ ≃ 1 − π 2 6 η 2 N in the vanishing small error limit η → 0 , which implies that complete order is never achieved for η > 0 . These results are supported by Monte Carlo simulations of the model, which allow to study other scenarios as well.Fil: Vazquez, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Cálculo; ArgentinaFil: Loscar, Ernesto Selim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Baglietto, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentin
Noisy multistate voter model for flocking in finite dimensions
We study a model for the collective behavior of self-propelled particles subject to pairwise copying interactions and noise. Particles move at a constant speed v on a two-dimensional space and, in a single step of the dynamics, each particle adopts the direction of motion of a randomly chosen neighboring particle within a distance R=1, with the addition of a perturbation of amplitude eta (noise). We investigate how the global level of particles' alignment (order) is affected by their motion and the noise amplitude eta. In the static case scenario v=0 where particles are fixed at the sites of a square lattice and interact with their first neighbors, we find that for any noise eta > 0 the system reaches a steady state of complete disorder in the thermodynamic limit, while for eta=0 full order is eventually achieved for a system with any number of particles N. Therefore, the model displays a transition at zero noise when particles are static, and thus there are no ordered steady states for a finite noise ( eta>0). We show that the finite-size transition noise vanishes with Nas eta_c^(1D)~ N^-1 and eta_c^(2D)~ (N lnN)^-1/2 in one- and two-dimensional lattices, respectively, which is linked to known results on the behavior of a type of noisy voter model for catalytic reactions. When particles are allowed to move in the space at a finite speed v>0, an ordered phase emerges, characterized by a fraction of particles moving in a similar direction. The system exhibits an order-disorder phase transition at a noise amplitude eta_c >0 that is proportional to v, and that scales approximately as eta_c ~ v(-lnv)^-1/2 for v<<1. These results show that the motion of particles is able to sustain a state of global order in a system with voter-like interactions.Fil: Loscar, Ernesto Selim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Baglietto, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Vazquez, Federico. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Calculo. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Calculo; Argentin
Species exclusion and coexistence in a noisy voter model with a competition-colonization tradeoff
We introduce an asymmetric noisy voter model to study the joint effect of
immigration and a competition-dispersal tradeoff in the dynamics of two species
competing for space in regular lattices. Individuals of one species can invade
a nearest-neighbor site in the lattice, while individuals of the other species
are able to invade sites at any distance but are less competitive locally,
i.e., they establish with a probability . The model also accounts for
immigration, modeled as an external noise that may spontaneously replace an
individual at a lattice site by another individual of the other species. This
combination of mechanisms gives rise to a rich variety of outcomes for species
competition, including exclusion of either species, mono-stable coexistence of
both species at different population proportions, and bi-stable coexistence
with proportions of populations that depend on the initial condition.
Remarkably, in the bi-stable phase, the system undergoes a discontinuous
transition as the intensity of immigration overcomes a threshold, leading to a
half loop dynamics associated to a cusp catastrophe, which causes the
irreversible loss of the species with the shortest dispersal range.Comment: 13 pages, 9 figures, 3 appendice
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