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M. J. Krawczyk

Publications and source records attributed to M. J. Krawczyk.

13 recordsLinked to original sources
arXiv2015

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.

physics.soc-ph↗
arXiv2014

If others jump to the queue front, how long I will wait?

Two models of a queue are proposed: a human queue and two lines of vehicles before a narrowing. In both models, a queuer tries to evaluate his waiting time, taking into account the delay caused by intruders who jump to the queue front. As the collected statistics of such events is very limited, the evaluation can give very long times. The results provide an example, when direct observations should be supplemented by an inference from the context.

physics.soc-ph↗
arXiv2014

Communities and classes in symmetric fractals

Two aspects of fractal networks are considered: the community structure and the class structure, where classes of nodes appear as a consequence of a local symmetry of nodes. The analysed systems are the networks constructed for two selected symmetric fractals: the Sierpinski triangle and the Koch curve. Communities are searched for by means of a set of differential equations. Overlapping nodes which belong to two different communities are identified by adding some noise to the initial connectivity matrix. Then, a node can be characterized by a spectrum of probabilities of belonging to different communities. Our main goal is that the overlapping nodes with the same spectra belong to the same class.

physics.comp-ph↗
arXiv2013

Influence of long-range interactions on strategy selection in crowd

An order--disorder phase transition is observed for Ising-like systems even for arbitrarily chosen probabilities of spins flips [K. Malarz et al, Int. J. Mod. Phys. C 22, 719 (2011)]. For such athermal dynamics one must define $(z+1)$ spin flips probabilities $w(n)$, where $z$ is a number of the nearest-neighbours for given regular lattice and $n=0,\cdots,z$ indicates the number of nearest spins with the same value as the considered spin. Recently, such dynamics has been successfully applied for the simulation of a cooperative and competitive strategy selection by pedestrians in crowd [P. Gawroński et al, Acta Phys. Pol. A 123, 522 (2013)]. For the triangular lattice ($z=6$) and flips probabilities dependence on a single control parameter $x$ chosen as $w(0)=1$, $w(1)=3x$, $w(2)=2x$, $w(3)=x$, $w(4)=x/2$, $w(5)=x/4$, $w(6)=x/6$ the ordered phase (where most of pedestrians adopt the same strategy) vanishes for $x>x_C\approx 0.429$. In order to introduce long-range interactions between pedestrians the bonds of triangular lattice are randomly rewired with the probability $p$. The amount of rewired bonds can be interpreted as the probability of communicating by mobile phones. The critical value of control parameter $x_C$ increases monotonically with the number of rewired links $M=pzN/2$ from $x_C(p=0)\approx 0.429$ to $x_C(p=1)\approx 0.81$.

physics.soc-ph↗
arXiv2012

Strategies in crowd and crowd structure

In an emergency situation, imitation of strategies of neighbours can lead to an order-disorder phase transition, where spatial clusters of pedestrians adopt the same strategy. We assume that there are two strategies, cooperating and competitive, which correspond to a smaller or larger desired velocity. The results of our simulations within the Social Force Model indicate that the ordered phase can be detected as an increase of spatial order of positions of the pedestrians in the crowd.

physics.soc-ph↗
arXiv2012

The Simmel effect and babies names

Simulations of the Simmel effect are performed for agents in a scale-free social network. The social hierarchy of an agent is determined by the degree of her node. Particular features, once selected by a highly connected agent, became common in lower class but soon fall out of fashion and extinct. Numerical results reflect the dynamics of frequency of American babies names in 1880-2011.

physics.soc-ph↗
arXiv2012

Combinatorial aspect of fashion

Simulations are performed according to the Axelrod model of culture dissemination, with modified mechanism of repulsion. Previously, repulsion was considered by Radillo-Diaz et al (Phys. Rev. E 80 (2009) 066107) as dependent on a predefined threshold. Here the probabilities of attraction and repulsion are calculated from the number of cells in the same states. We also investigate the influence of some homogeneity, introduced to the initial state. As the result of the probabilistic definition of repulsion, the ordered state vanishes. A small cluster of a few percent of population is retained only if in the initial state a set of agents is prepared in the same state. We conclude that the modelled imitation is successful only with respect to agents, and not only their features.

physics.soc-ph↗
arXiv2010

Situations in traffic - how quickly they change

Spatio-temporal correlations of intensity of traffic are analysed for one week data collected in the motorway M-30 around Madrid in January 2009. We found that the lifetime of these correlations is the shortest in the evening, between 6 and 8 p.m. This lifetime is a new indicator how much attention of drivers is demanded in given traffic conditions.

physics.comp-ph↗
arXiv2010

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.

physics.soc-ph↗
arXiv2009

Altruism and reputation: cooperation within groups

In our recent model, the cooperation emerges as a positive feedback between a not-too-bad reputation and an altruistic attitude. Here we introduce a bias of altruism as to favorize members of the same group. The matrix F(i,j) of frequency of cooperation between agents i and j reveals the structure of communities. The Newman algorithm reproduces the initial bias. The method based on differential equations detects two groups of agents cooperating within their groups, leaving the uncooperative ones aside.

physics.soc-ph↗
arXiv2004

Spin glass properties of an Ising antiferromagnet on the Archimedean (3,12^2) lattice

We investigate magnetic properties of a two-dimensional periodic structure with Ising spins and antiferromagnetic nearest neighbor interaction. The structure is topologically equivalent to the Archimedean (3,12^2) lattice. The ground state energy is degenerate. In some ground states, the spin structure is translationally invariant, with the same configuration in each unit cell. Numerical results are reported on specific heat and static magnetic usceptibility against temperature. Both quantities show maxima at temperature T>0. They reveal some sensitivity on the initial state in temperatures where the Edwards--Anderson order parameter is positive. For zero temperature and low frequency of the applied field, the magnetic losses are negligible. However, the magnetization curve displays some erratic behavior due to the metastable states.

cond-mat.stat-mech↗
arXiv2004

Off-lattice simulation of the solid phase DNA amplification

Recent simulations of the solid phase DNA amplification (SPA) by J.-F. Mercier et al (Biophys. J. 85 (2003) 2075) are generalized to include two kinds of primers and the off-lattice character of the primer distribution on the surface. The sigmoidal character of the primer occupation by DNA, observed experimentally, is reproduced in the simulation. We discuss an influence of two parameters on the efficience of the amplification process: the initial density p_0 of the occupied primers from the interfacial amplification and the ratio r of the molecule length to the average distance between primers. The number of cycles till the saturation decreases with p_0 roughly as p_0^{-0.26}. For r=1.5, the number of occupied primers is reduced by a factor two, when compared to the case of longer molecules. Below r=1.4, the effectivity of SPA is reduced by a factor 100.

q-bio.BM↗