102 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
Majority-vote model on (3,4,6,4) and (3^4,6) Archimedean lattices
On Archimedean lattices, the Ising model exhibits spontaneous ordering. Two
examples of these lattices of the majority-vote model with noise are considered
and studied through extensive Monte Carlo simulations. The order/disorder phase
transition is observed in this system. The calculated values of the critical
noise parameter are q_c=0.091(2) and q_c=0.134(3) for (3,4,6,4) and (3^4,6)
Archimedean lattices, respectively. The critical exponents beta/nu, gamma/nu
and 1/nu for this model are 0.103(6), 1.596(54), 0.872(85) for (3,4,6,4) and
0.114(3), 1.632(35), 0.978(104) for (3^4,6) Archimedean lattices. These results
differs from the usual Ising model results and the majority-vote model on
so-far studied regular lattices or complex networks. The effective
dimensionality of the system [D_{eff}(3,4,6,4)=1.802(55) and
D_{eff}(3^4,6)=1.860(34)] for these networks are reasonably close to the
embedding dimension two.Comment: 6 pages, 7 figures in 12 eps files, RevTex
Avalanches in complex spin networks
We investigate the magnetization reversal processes on classes of complex
spin networks with antiferromagnetic interaction along the network links. With
slow field ramping the hysteresis loop and avalanches of spin flips occur due
to topological inhomogeneity of the network, even without any disorder of the
magnetic interaction [B. Tadic, et al., Phys. Rev. Lett. 94 (2005) 137204].
Here we study in detail properties of the magnetization avalanches, hysteresis
curves and density of domain walls and show how they can be related to the
structural inhomogeneity of the network. The probability distribution of the
avalanche size, N_s(s), displays the power-law behaviour for small s, i.e.
N_s(s)\propto s^{-\alpha}. For the scale-free networks, grown with preferential
attachment, \alpha increases with the connectivity parameter M from 1.38 for
M=1 (trees) to 1.52 for M=25. For the exponential networks, \alpha is close to
1.0 in the whole range of M.Comment: 16 pages, 10 figures in 29 eps file
Recovering Zipf's law in intercontinental scientific collaboration
Scientific cooperation on an international level has been well studied in the
literature. However, much less is known about this cooperation on the
intercontinental level. In this paper, we address this issue by creating a
collection of approximately 13.8 million publications around the papers by one
of the highly cited author working in complex networks and their applications.
The obtained rank-frequency distribution of the probability of sequences
describing continents and number of countries -- with which authors of papers
are affiliated -- follows the power law with an exponent . Such a
dependence is known in the literature as Zipf's law and it has been originally
observed in linguistics, later it turned out that it is very commonly observed
in various fields. The number of distinct ``continent (number of countries)''
sequences in a function of the number of analyzed papers grows according to
power law with exponent , i.e. it follows Heap's law.Comment: 6 pages, 3 figures, 4 table
Reshuffling spins with short range interactions: When sociophysics produces physical results
Galam reshuffling introduced in opinion dynamics models is investigated under
the nearest neighbor Ising model on a square lattice using Monte Carlo
simulations. While the corresponding Galam analytical critical temperature T_C
\approx 3.09 [J/k_B] is recovered almost exactly, it is proved to be different
from both values, not reshuffled (T_C=2/arcsinh(1) \approx 2.27 [J/k_B]) and
mean-field (T_C=4 [J/k_B]). On this basis, gradual reshuffling is studied as
function of 0 \leq p \leq 1 where p measures the probability of spin
reshuffling after each Monte Carlo step. The variation of T_C as function of p
is obtained and exhibits a non-linear behavior. The simplest Solomon network
realization is noted to reproduce Galam p=1 result. Similarly to the critical
temperature, critical exponents are found to differ from both, the classical
Ising case and the mean-field values.Comment: 11 pages, 5 figures in 6 eps files, to appear in IJMP
Square lattice site percolation at increasing ranges of neighbor interactions
We report site percolation thresholds for square lattice with neighbor
interactions at various increasing ranges. Using Monte Carlo techniques we
found that nearest neighbors (N), next nearest neighbors (N), next next
nearest neighbors (N) and fifth nearest neighbors (N) yield the same
. At odds, fourth nearest neighbors (N) give .
These results are given an explanation in terms of symmetry arguments. We then
consider combinations of various ranges of interactions with (N+N),
(N+N), (N+N+N) and (N+N). The calculated associated
thresholds are respectively . The
existing Galam--Mauger universal formula for percolation thresholds does not
reproduce the data showing dimension and coordination number are not sufficient
to build a universal law which extends to complex lattices.Comment: 4 pages, revtex
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
Scaling properties of the Penna model
We investigate the scaling properties of the Penna model, which has become a
popular tool for the study of population dynamics and evolutionary problems in
recent years. We find that the model generates a normalised age distribution
for which a simple scaling rule is proposed, that is able to reproduce
qualitative features for all genome sizes.Comment: 4 pages, 4 figure
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