122 research outputs found
Ising model on two connected Barabasi-Albert networks
We investigate analytically the behavior of Ising model on two connected
Barabasi-Albert networks. Depending on relative ordering of both networks there
are two possible phases corresponding to parallel or antiparallel alingment of
spins in both networks. A difference between critical temperatures of both
phases disappears in the limit of vanishing inter-network coupling for
identical networks. The analytic predictions are confirmed by numerical
simulations.Comment: 6 pages including 6 figure
Coevolution of Information Processing and Topology in Hierarchical Adaptive Random Boolean Networks
Random Boolean networks (RBNs) are frequently employed for modelling complex
systems driven by information processing, e.g. for gene regulatory networks
(GRNs). Here we propose a hierarchical adaptive RBN (HARBN) as a system
consisting of distinct adaptive RBNs - subnetworks - connected by a set of
permanent interlinks. Information measures and internal subnetworks topology of
HARBN coevolve and reach steady-states that are specific for a given network
structure. We investigate mean node information, mean edge information as well
as a mean node degree as functions of model parameters and demonstrate HARBN's
ability to describe complex hierarchical systems.Comment: 9 pages, 6 figure
Modelling Collective Opinion Formation by Means of Active Brownian Particles
The concept of active Brownian particles is used to model a collective
opinion formation process. It is assumed that individuals in community create a
two-component communication field that influences the change of opinions of
other persons and/or can induce their migration. The communication field is
described by a reaction-diffusion equation, the opinion change of the
individuals is given by a master equation, while the migration is described by
a set of Langevin equations, coupled by the communication field. In the
mean-field limit holding for fast communication we derive a critical population
size, above which the community separates into a majority and a minority with
opposite opinions. The existence of external support (e.g. from mass media)
changes the ratio between minority and majority, until above a critical
external support the supported subpopulation exists always as a majority.
Spatial effects lead to two critical ``social'' temperatures, between which the
community exists in a metastable state, thus fluctuations below a certain
critical wave number may result in a spatial opinion separation. The range of
metastability is particularly determined by a parameter characterizing the
individual response to the communication field. In our discussion, we draw
analogies to phase transitions in physical systems.Comment: Revised text version. Accepted for publication in European Physics
Journal B. For related work see
http://summa.physik.hu-berlin.de/~frank/active.html and
http://www.if.pw.edu.pl/~jholys
Opinion dynamics driven by leaders, media, viruses and worms
A model on the effects of leader, media, viruses, and worms and other agents
on the opinion of individuals is developed and utilized to simulate the
formation of consensus in society and price in market via excess between supply
and demand. Effects of some time varying drives, (harmonic and hyperbolic) are
also investigated.
Key words: Opinion; Leader; Media; Market; Buyers; Sellers; ExcessComment: 14 pages, 7 figures (14, total) Will be published in IJMP
Ferromagnetic fluid as a model of social impact
The paper proposes a new model of spin dynamics which can be treated as a
model of sociological coupling between individuals. Our approach takes into
account two different human features: gregariousness and individuality. We will
show how they affect a psychological distance between individuals and how the
distance changes the opinion formation in a social group. Apart from its
sociological aplications the model displays the variety of other interesting
phenomena like self-organizing ferromagnetic state or a second order phase
transition and can be studied from different points of view, e.g. as a model of
ferromagnetic fluid, complex evolving network or multiplicative random process.Comment: 8 pages, 5 figure
Shock waves in one-dimensional Heisenberg ferromagnets
We use SU(2) coherent state path integral formulation with the stationary
phase approximation to investigate, both analytically and numerically, the
existence of shock waves in the one- dimensional Heisenberg ferromagnets with
anisotropic exchange interaction. As a result we show the existence of shock
waves of two types,"bright" and "dark", which can be interpreted as moving
magnetic domains.Comment: 10 pages, with 3 ps figure
The critical properties of the agent-based model with environmental-economic interactions
The steady-state and nonequilibrium properties of the model of
environmental-economic interactions are studied. The interacting heterogeneous
agents are simulated on the platform of the emission dynamics of cellular
automaton. The model possess the discontinuous transition between the safe and
catastrophic ecology. Right at the critical line, the broad-scale power-law
distributions of emission rates have been identified. Their relationship to
Zipf's law and models of self-organized criticality is discussed.Comment: 12 pages, 6 figures, published in Physica
Polydispersity and ordered phases in solutions of rodlike macromolecules
We apply density functional theory to study the influence of polydispersity
on the stability of columnar, smectic and solid ordering in the solutions of
rodlike macromolecules. For sufficiently large length polydispersity (standard
deviation ) a direct first-order nematic-columnar transition is
found, while for smaller there is a continuous nematic-smectic and
first-order smectic-columnar transition. For increasing polydispersity the
columnar structure is stabilized with respect to solid perturbations. The
length distribution of macromolecules changes neither at the nematic-smectic
nor at the nematic-columnar transition, but it does change at the
smectic-columnar phase transition. We also study the phase behaviour of binary
mixtures, in which the nematic-smectic transition is again found to be
continuous. Demixing according to rod length in the smectic phase is always
preempted by transitions to solid or columnar ordering.Comment: 13 pages (TeX), 2 Postscript figures uuencode
Opinion Dynamics of Learning Agents: Does Seeking Consensus Lead to Disagreement?
We study opinion dynamics in a population of interacting adaptive agents
voting on a set of complex multidimensional issues. We consider agents which
can classify issues into for or against. The agents arrive at the opinions
about each issue in question using an adaptive algorithm. Adaptation comes from
learning and the information for the learning process comes from interacting
with other neighboring agents and trying to change the internal state in order
to concur with their opinions. The change in the internal state is driven by
the information contained in the issue and in the opinion of the other agent.
We present results in a simple yet rich context where each agent uses a Boolean
Perceptron to state its opinion. If there is no internal clock, so the update
occurs with asynchronously exchanged information among pairs of agents, then
the typical case, if the number of issues is kept small, is the evolution into
a society thorn by the emergence of factions with extreme opposite beliefs.
This occurs even when seeking consensus with agents with opposite opinions. The
curious result is that it is learning from those that hold the same opinions
that drives the emergence of factions. This results follows from the fact that
factions are prevented by not learning at all from those agents that hold the
same opinion. If the number of issues is large, the dynamics becomes trapped
and the society does not evolve into factions and a distribution of moderate
opinions is observed. We also study the less realistic, but technically simpler
synchronous case showing that global consensus is a fixed point. However, the
approach to this consensus is glassy in the limit of large societies if agents
adapt even in the case of agreement.Comment: 16 pages, 10 figures, revised versio
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