arXiv subjects

Krzysztof Kulakowski

Publications and source records attributed to Krzysztof Kulakowski.

46 records · Page 3Linked to original sources

arXiv2007

Clusterization, frustration and collectivity in random networks

We consider the random Erd{\H o}s--Rényi network with enhanced clusterization and Ising spins $s=\pm 1$ at the network nodes. Mutually linked spins interact with energy $J$. Magnetic properties of the system as dependent on the clustering coefficient $C$ are investigated with the Monte Carlo heat bath algorithm. For $J>0$ the Curie temperature $T_c$ increases from 3.9 to 5.5 when $C$ increases from almost zero to 0.18. These results deviate only slightly from the mean field theory. For $J<0$ the spin-glass phase appears below $T_{SG}$; this temperature decreases with $C$, on the contrary to the mean field calculations. The results are interpreted in terms of social systems.

physics.soc-ph↗

arXiv2007

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.

physics.soc-ph↗

arXiv2007

Some recent attempts to simulate the Heider balance problem

The Heider balance is a sociological problem of a division of a community into hostile groups, where all interpersonal relations within the groups are friendly and all relations between the members of different groups are hostile. Here we trace how the research of the process of attaining the Heider balance has moved during last ten years from a psycho-social to a computational problem.

physics.soc-ph↗

arXiv2006

Phase transition in Nowak-Sznajd opinion dynamics

The Nowak modification of the Sznajd opinion dynamics model on the square lattice assumes that with probabilities beta and gamma the opinions flip due to mass-media advertising from down to up, and vice versa. Besides, with probability alpha the Sznajd rule applies that a neighbour pair agreeing in its two opinions convinces all its six neighbours of that opinion. Our Monte Carlo simulations and mean-field theory find sharp phase transitions in the parameter space.

physics.soc-ph↗

arXiv2006

Efficiency of pair formation in a model society

In a recent paper a set of differential equations was proposed to describe a social process, where pairs of partners emerge in a community. The choice was performed on a basis of attractive resources and of random initial preferences. An efficiency of the process, defined as the probability of finding a partner, was found to depend on the community size. Here we demonstrate, that if the resources are not relevant, the efficiency is equal to unity; everybody finds a partner. With this new formulation, about 80 percent of community members enter to dyads; the remaining 20 percent form triads.

physics.soc-ph↗

arXiv2006

Remanence and switching sensitivity in nanodot magnetic arrays

New results are reported of the computer simulations on the magnetic behaviour of magnetic arrays of nanoscopic dots, placed in cells of the square lattice. We show that the remanence magnetization $M_r$ decreases with the array size. For arrays 50x50, we investigate also the stability of the magnetic structure of an array in an oscillating magnetic field. The damage spreading technique reveals that this stability increases with the standard deviation $σ$ of the switching field of individual elements of the array. On the other hand, $M_r$ decreases with $σ$. An optimalization of the system (large $M_r$ and large stability) can then be reached at some intermediate value of $σ$.

cond-mat.mtrl-sci↗

arXiv2005

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.

physics.soc-ph↗

arXiv2005

How political parties adjust to fixed voter opinions

We propose a new version of the spatial model of voting. Platforms of five parties are evolving in a two-dimensional landscape of political issues so as to get maximal numbers of voters. For a Gaussian landscape the evolution leads to a spatially symmetric state, where the platform centers form a pentagon around the Gaussian peak. For a bimodal landscape the platforms located at different peaks get different numbers of voters.

physics.soc-ph↗

arXiv2005

Transition from Uniform Motion to Stick-Slip in the Rice-Ruina Model of One and Two Blocks

We analyze the Rice-Ruina state and rate dependent friction model. The system consists of one or two blocks driven by springs with constant velocity on a dry, rough surface. Our discussion is limited to the creep-like motion, when the driving velocity is small. Two regimes of motion are observed: stick-slip and steady sliding. The stability of the steady sliding depends on the model parameters. Numerical and analytical results show a transition between two regimes: the system passes directly from uniform to stick-slip motion. The calculations are performed also for two driven blocks. Then, the transition has the same character and it appears at the same point.

nlin.SI↗

arXiv2005

The Heider balance - a continuous approach

The Heider balance (HB) is investigated in a fully connected graph of $N$ nodes. The links are described by a real symmetric array r(i,j), i,j=1,...,N. In a social group, nodes represent group members and links represent relations between them, positive (friendly) or negative (hostile). At the balanced state, r(i,j)r(j,k)r(k,i)>0 for all the triads (i,j,k). As follows from the structure theorem of Cartwright and Harary, at this state the group is divided into two subgroups, with friendly internal relations and hostile relations between the subgroups. Here the system dynamics is proposed to be determined by a set of differential equations. The form of equations guarantees that once HB is reached, it persists. Also, for N=3 the dynamics reproduces properly the tendency of the system to the balanced state. The equations are solved numerically. Initially, r(i,j) are random numbers distributed around zero with a symmetric uniform distribution of unit width. Calculations up to N=500 show that HB is always reached. Time to get the balanced state varies with the system size N as N^{-1/2}. The spectrum of relations, initially narrow, gets very wide near HB. This means that the relations are strongly polarized. In our calculations, the relations are limited to a given range around zero. With this limitation, our results can be helpful in an interpretation of somestatistical data.

physics.soc-ph↗