516 research outputs found
Simulation of Consensus Model of Deffuant et al on a Barabasi-Albert Network
In the consensus model with bounded confidence, studied by Deffuant et al.
(2000), two randomly selected people who differ not too much in their opinion
both shift their opinions towards each other. Now we restrict this exchange of
information to people connected by a scale-free network. As a result, the
number of different final opinions (when no complete consensus is formed) is
proportional to the number of people.Comment: 7 pages including 3 figs; Int.J.MOd.Phys.C 15, issue 2; programming
error correcte
Exact decoherence to pointer states in free open quantum systems is universal
In this paper it is shown that exact decoherence to minimal uncertainty
Gaussian pointer states is generic for free quantum particles coupled to a heat
bath. More specifically, the paper is concerned with damped free particles
linearly coupled under product initial conditions to a heat bath at arbitrary
temperature, with arbitrary coupling strength and spectral densities covering
the Ohmic, subohmic, and supraohmic regime. Then it is true that there exists a
time t_c such that for times t>t_c the state can always be exactly represented
as a mixture (convex combination) of particular minimal uncertainty Gaussian
states, regardless of and independent from the initial state. This exact
`localisation' is hence not a feature specific to high temperatures and weak
damping limit, but is rather a generic property of damped free particles.Comment: 4 pages, 1 figur
Ballistic transport and surface scattering in (In,Ga)As-InP heterostructure narrow channels
Narrow conduction channels are fabricated from an In0.75Ga0.25As-InP heterostructure using electron-beam lithography and dry etching. The etched surface is realized to be smooth by employing a reactive ion etching. The etching-induced surface conduction is eliminated by removing the damaged surface layer using a diluted HCl solution. The negligible surface depletion for the In-rich quantum well enables to create conducting channels in arbitrary geometries such as in a circular shape. We evidence the presence of a ballistic contribution in the electron transport by demonstrating a rectification of rf excitations that is achieved by the magnetic-field-tuned transmission asymmetry in the circularly-shaped channels. The absence of the surface depletion is shown to cause, on the other hand, a surface scattering for the electrons confined in the channels. An increase of the resistance, including its anomalous enhancement at low temperatures, is induced by the gas molecules attached to the sidewalls of the channels. We also report a large persistent photoconduction, which occurs as a parallel conduction in the undoped InP barrier layer.Peer Reviewe
Opinion dynamics: rise and fall of political parties
We analyze the evolution of political organizations using a model in which
agents change their opinions via two competing mechanisms. Two agents may
interact and reach consensus, and additionally, individual agents may
spontaneously change their opinions by a random, diffusive process. We find
three distinct possibilities. For strong diffusion, the distribution of
opinions is uniform and no political organizations (parties) are formed. For
weak diffusion, parties do form and furthermore, the political landscape
continually evolves as small parties merge into larger ones. Without diffusion,
a pattern develops: parties have the same size and they possess equal niches.
These phenomena are analyzed using pattern formation and scaling techniques.Comment: 5 pages, 5 figure
Intracultural diversity in a model of social dynamics
We study the consequences of introducing individual nonconformity in social
interactions, based on Axelrod's model for the dissemination of culture. A
constraint on the number of situations in which interaction may take place is
introduced in order to lift the unavoidable ho mogeneity present in the final
configurations arising in Axelrod's related models. The inclusion of this
constraint leads to the occurrence of complex patterns of intracultural
diversity whose statistical properties and spatial distribution are
characterized by means of the concepts of cultural affinity and cultural cli
ne. It is found that the relevant quantity that determines the properties of
intracultural diversity is given by the fraction of cultural features that
characterizes the cultural nonconformity of individuals.Comment: 7 pages, 2 tables, 6 figure
Cooperation and defection in ghetto
We consider ghetto as a community of people ruled against their will by an
external power. Members of the community feel that their laws are broken.
However, attempts to leave ghetto makes their situation worse. We discuss the
relation of the ghetto inhabitants to the ruling power in context of their
needs, organized according to the Maslow hierarchy. Decisions how to satisfy
successive needs are undertaken in cooperation with or defection the ruling
power. This issue allows to construct the tree of decisions and to adopt the
pruning technique from the game theory. Dynamics of decisions can be described
within the formalism of fundamental equations. The result is that the strategy
of defection is stabilized by the estimated payoff.Comment: 12 pages, 2 figure
Dynamics of Dissipative Quantum Systems--from Path Integrals to Master Equations
The path integral approach offers not only an exact expression for the non-
equilibrium dynamics of dissipative quantum systems, but is also a convenient
starting point for perturbative treatments. An alternative way to explore the
influence of friction in the quantum realm is based on master equations which
require, however, in one or the other aspect approximations. Here it is
discussed under which conditions and limitations Markovian master equations can
be derived from exact path integrals thus providing a firm basis for their
applicability.Comment: 10 pages, 1 figur
Van Kampen's expansion approach in an opinion formation model
We analyze a simple opinion formation model consisting of two parties, A and
B, and a group I, of undecided agents. We assume that the supporters of parties
A and B do not interact among them, but only interact through the group I, and
that there is a nonzero probability of a spontaneous change of opinion (A->I,
B->I). From the master equation, and via van Kampen's Omega-expansion approach,
we have obtained the "macroscopic" evolution equation, as well as the
Fokker-Planck equation governing the fluctuations around the deterministic
behavior. Within the same approach, we have also obtained information about the
typical relaxation behavior of small perturbations.Comment: 17 pages, 6 figures, submited to Europ.Phys.J.
- âŠ