71 research outputs found
Heavy context dependence---decisions of underground soldiers
An attempt is made to simulate the disclosure of underground soldiers in
terms of theory of networks. The coupling mechanism between the network nodes
is the possibility that a disclosed soldier is going to disclose also his
acquaintances. We calculate the fraction of disclosed soldiers as dependent on
the fraction of those who, once disclosed, reveal also their colleagues. The
simulation is immersed in the historical context of the Polish Home Army under
the communist rule in 1946-49.Comment: 7 pages, 5 figures, for the European Conference on Modelling and
Simulation (ECMS 2015
Evacuation in the Social Force Model is not stationary
An evacuation process is simulated within the Social Force Model. Thousand
pedestrians are leaving a room by one exit. We investigate the stationarity of
the distribution of time lags between instants when two successive pedestrians
cross the exit. The exponential tail of the distribution is shown to gradually
vanish. Taking fluctuations apart, the time lags decrease in time till there
are only about 50 pedestrians in the room, then they start to increase. This
suggests that at the last stage the flow is laminar. In the first stage,
clogging events slow the evacuation down. As they are more likely for larger
crowds, the flow is not stationary. The data are investigated with detrended
fluctuation analysis.Comment: 7 pages, 3 figures; PACS numbers: 89.75.Fb, 05.40.-a, 05.45.Tp,
89.40.B
Communication and trust in the bounded confidence model
The communication process in a situation of emergency is discussed within the
Scheff theory of shame and pride. The communication involves messages from
media and from other persons. Three strategies are considered: selfish (to
contact friends), collective (to join other people) and passive (to do
nothing). We show that the pure selfish strategy cannot be evolutionarily
stable. The main result is that the community structure is statistically
meaningful only if the interpersonal communication is weak.Comment: 6 pages, 5 figures, RevTeX, for ICCCI-201
Average distance in growing trees
Two kinds of evolving trees are considered here: the exponential trees, where
subsequent nodes are linked to old nodes without any preference, and the
Barab\'asi--Albert scale-free networks, where the probability of linking to a
node is proportional to the number of its pre-existing links. In both cases,
new nodes are linked to nodes. Average node-node distance is
calculated numerically in evolving trees as dependent on the number of nodes
. The results for not less than a thousand are averaged over a thousand
of growing trees. The results on the mean node-node distance for large
can be approximated by for the exponential trees, and
for the scale-free trees, where the are constant. We
derive also iterative equations for and its dispersion for the exponential
trees. The simulation and the analytical approach give the same results.Comment: 6 pages, 3 figures, Int. J. Mod. Phys. C14 (2003) - in prin
How pairs of partners emerge in an initially fully connected society
A social group is represented by a graph, where each pair of nodes is
connected by two oppositely directed links. At the beginning, a given amount
of resources is assigned randomly to each node . Also, each link
is initially represented by a random positive value, which means the
percentage of resources of node which is offered to node . Initially
then, the graph is fully connected, i.e. all non-diagonal matrix elements
are different from zero. During the simulation, the amounts of
resources change according to the balance equation. Also, nodes
reorganise their activity with time, going to give more resources to those
which give them more. This is the rule of varying the coefficients .
The result is that after some transient time, only some pairs of nodes
survive with non-zero and , each pair with symmetric and positive
. Other coefficients vanish. Unpaired nodes remain
with no resources, i.e. their , and they cease to be active, as they
have nothing to offer. The percentage of survivors (i.e. those with with
positive) increases with the velocity of varying the numbers , and it
slightly decreases with the size of the group. The picture and the results can
be interpreted as a description of a social algorithm leading to marriages.Comment: 7 pages, 3 figure
New algorithm for the computation of the partition function for the Ising model on a square lattice
A new and efficient algorithm is presented for the calculation of the
partition function in the Ising model. As an example, we use the
algorithm to obtain the thermal dependence of the magnetic spin susceptibility
of an Ising antiferromagnet for a square lattice with open boundary
conditions. The results agree qualitatively with the prediction of the Monte
Carlo simulations and with experimental data and they are better than the mean
field approach results. For the lattice, the algorithm reduces the
computation time by nine orders of magnitude.Comment: 7 pages, 3 figures, to appear in Int. J. Mod. Phys.
Cops or robbers - a bistable society
The norm game described by Axelrod in 1985 was recently treated with the
master equation formalism. Here we discuss the equations, where {\it i)} those
who break the norm cannot punish and those who punish cannot break the norm,
{\it ii)} the tendency to punish is suppressed if the majority breaks the norm.
The second mechanism is new. For some values of the parameters the solution
shows the saddle-point bifurcation. Then, two stable solutions are possible,
where the majority breaks the norm or the majority punishes. This means, that
the norm breaking can be discontinuous, when measured in the social scale. The
bistable character is reproduced also with new computer simulations on the
Erd{\H o}s--R\'enyi directed network.Comment: 8 pages, 2 figures. Some misleading sentences are removed from
section
Magnetization reversal in spin patterns with complex geometry
We study field-driven dynamics of spins with antiferromagnetic interaction
along the links of a complex substrate geometry, which is modeled by graphs of
a controlled connectivity distribution. The magnetization reversal occurs in
avalanches of spin flips, which are pinned by the topological constraints of
the underlying graph. The hysteresis loop and avalanche sizes are analyzed and
classified in terms of graph's connectivity and clustering. The results are
relevant for magnets with a hierarchical spatial inhomogeneity and for design
of nanoscale magnetic devices.Comment: 4 pages, 3 color figures, revtex
The Galam Model of Minority Opinion Spreading and the Marriage Gap
In 2002, Serge Galam designed a model of a minority opinion spreading. The
effect is expected to lead a conservative minority to prevail if the issue is
discussed long enough. Here we analyze the marriage gap, i.e. the difference in
voting for Bush and Kerry in 2004 between married and unmarried people. It
seems possible to interpret this marriage gap in terms of the Galam model.Comment: 6 page
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