The ground-state of an infinite-range Potts glass-type model with ±J bonds and unrestricted numbe... more The ground-state of an infinite-range Potts glass-type model with ±J bonds and unrestricted number of states is used to investigate coalition formation. As a function of the q probability of +J bonds in the system it is found that the r relative size of the largest cluster (a cluster being the group of elements in the same state) shows a percolation like behavior. By a simple renormalization approach and several optimization methods we investigate the r(q) curves for finite systems sizes. Non-trivial consequences for social percolation problems are discussed. 87.23 Ge (Dynamics of social systems), 75.50.Lk (Spin glasses and other random magnets)
Evaporation of a small glass of ethylic alcohol is studied both experimentally and through an ele... more Evaporation of a small glass of ethylic alcohol is studied both experimentally and through an elementary thermal physics approach. For a cylindrical beaker and no air flow in the room, a simple quadratic relation is found between the evaporation time and the mass of evaporated liquid. This problem and the obtained results offer excellent possibilities for simple student experiments and for testing basic principles of thermal physics. As an example, we use the obtained results for estimating the value of the Boltzmann constant from evaporation experiments.
We reverse engineer entropy formulas from entropic divergence, optimized to given classes of prob... more We reverse engineer entropy formulas from entropic divergence, optimized to given classes of probability distribution function (PDF) evolution dynamical equation. For linear dynamics of the distribution function, the traditional Kullback–Leibler formula follows from using the logarithm function in the Csiszár’s f-divergence construction, while for nonlinear master equations more general formulas emerge. As applications, we review a local growth and global reset (LGGR) model for citation distributions, income distribution models and hadron number fluctuations in high energy collisions.
Using the Swendsen and Wang algorithm, high accuracy Monte Carlo simulations were performed to st... more Using the Swendsen and Wang algorithm, high accuracy Monte Carlo simulations were performed to study the concentration dependence of the Curie temperature in binary, ferromagnetic Ising systems on the simple-cubic lattice. Our results are in good agreement with known mean-field like approaches. Based on former theoretical formulas we propose a new way of estimating the Curie temperature of these systems.
The topology and dynamics of stripe-like magnetic domains obtained in a ferrimagnetic garnet subj... more The topology and dynamics of stripe-like magnetic domains obtained in a ferrimagnetic garnet subjected to a time-dependent external magnetic field is studied experimentally and theoretically. Experiments are performed on a commercially available magnetic bubble apparatus, allowing the observation of the time-evolution of the magnetic domain structure. The system is modeled by a meso-scale Ising-type lattice model. Exchange and dipolar interactions between the spins, and interaction of the spins with the external magnetic field are considered. The model is investigated by kinetic Monte Carlo simulations with time-varying transition rates. In the limit of low temperatures the elaborated model leads to a magnetic domain topology and dynamics that is similar to the ones observed in the experiments. In the highly non-equilibrium limit with a high driving frequency the model reproduces the experimentally recorded hysteresis loops as well.
Physica A: Statistical Mechanics and its Applications, 2007
The distribution of wealth in the Hungarian medieval aristocratic society is reported and studied... more The distribution of wealth in the Hungarian medieval aristocratic society is reported and studied. The number of serf families belonging to a noble is taken as a measure of the corresponding wealth. Our results reveal the power-law nature of this distribution function, confirming the validity of the Pareto law for such a society. The obtained Pareto index α = 0.92 is however smaller than the values currently reported in the literature. We argue that the value close to 1, of the Pareto index is a consequence of the absence of a relevant economic life in the targeted society, in agreement with the prediction of existing wealth distribution models for the idealized case of independently acting agents. Models developed to explain city populations may also be adapted to justify our results.
The dynamics of a spring-block train placed on a moving conveyor belt is investigated both by sim... more The dynamics of a spring-block train placed on a moving conveyor belt is investigated both by simple experiments and computer simulations. The first block is connected by spring to an external static point, and due to the dragging effect of the belt the blocks undergo complex stickslip dynamics. A qualitative agreement with the experimental results can only be achieved by taking into account the spatial inhomogeneity of the friction force on the belt's surface, modeled as noise. As a function of the velocity of the conveyor belt and the noise strength, the system exhibits complex, self-organized critical, sometimes chaotic dynamics and phase transition-like behavior. Noise induced chaos and intermittency is also observed. Simulations suggest that the maximum complexity of the dynamical states is achieved for a relatively small number of blocks, around five.
The phase-space of a simple synchronization model is thoroughly investigated. The model considers... more The phase-space of a simple synchronization model is thoroughly investigated. The model considers two-mode stochastic oscillators, coupled through a pulse-like interaction controlled by simple optimization rules. A complex phase space is uncovered as a function of two relevant model parameters that are related to the optimization threshold and the periods of the two oscillation modes. Several phases with different periodic global output signals are identified. It is shown that the system exhibits partial synchronization under unexpectedly general conditions.
Physica A: Statistical Mechanics and its Applications, 2007
This article was published in an Elsevier journal. The attached copy is furnished to the author f... more This article was published in an Elsevier journal. The attached copy is furnished to the author for non-commercial research and education use, including for instruction at the author's institution, sharing with colleagues and providing to institution administration. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit:
We consider two external laser beams interfering inside a n-GaAs with a nonlinear feedback. In a ... more We consider two external laser beams interfering inside a n-GaAs with a nonlinear feedback. In a given parameter region coexistence of the two unstable periodic domain trains (UPDTs) is found in this system. The UPDT is associated with the formation of intermittent oscillating current in the circuit. By external periodic driving, a novel resonance is observed in both inside one UPDT and the switching between the two UPDTs. The signal-to-noise ratio (SNR) as a function of driving amplitude A is numericaly investigated and the nonmonotonic behavior of the SNR(A) spectrum is observed.
Modelling and Simulation in Materials Science and Engineering, 1997
A new Monte Carlo method is described for studying the equilibrium shapes of fluids on solid surf... more A new Monte Carlo method is described for studying the equilibrium shapes of fluids on solid surfaces when the contact angles on the surface are smaller or equal to π/2. The method minimizes the energy of the system by consecutively applying two distinct annealing mechanisms. The method is tested for some simple analytically solvable cases and, as an example, applied to a more complex geometry.
The average travelling speed increases in a nontrivial manner with the travel distance. This lead... more The average travelling speed increases in a nontrivial manner with the travel distance. This leads to scaling-like relations on quite extended spatial scales, for all mobility modes taken together and also for a given mobility mode in part. We offer a wide range of experimental results, investigating and quantifying this universal effect and its measurable causes. The increasing travelling speed with the travel distance arises from the combined effects of: choosing the most appropriate travelling mode; the structure of the travel networks; the travel times lost in the main hubs, starting or target cities; and the speed limit of roads and vehicles.
Spontaneous synchronization of an ensemble of metronomes placed on a freely rotating platform is ... more Spontaneous synchronization of an ensemble of metronomes placed on a freely rotating platform is studied experimentally and by computer simulations. A striking in-phase synchronization is observed when the metronomes' beat frequencies are fixed above a critical limit. Increasing the number of metronomes placed on the disk leads to an observable decrease in the level of the emerging synchronization. A realistic model with experimentally determined parameters is considered in order to understand the observed results. The conditions favoring the emergence of synchronization are investigated. It is shown that the experimentally observed trends can be reproduced by assuming a finite spread in the metronomes' natural frequencies. In the limit of large numbers of metronomes, we show that synchronization emerges only above a critical beat frequency value.
Oscillation and collective behavior in convection-driven fluid columns are investigated and discu... more Oscillation and collective behavior in convection-driven fluid columns are investigated and discussed in analogy with similar phenomenon observed for the flickering flames of candle bundles. It is shown experimentally that an ascending circular Helium gas column performs an oscillation which is similar in several aspects to the oscillation of diffusion flames. Increasing the nozzle diameter leads to a decrease in the oscillation frequency, while increasing the flow rate results in an increase in this frequency. For helium columns oscillating at nearby frequency and placed close to each other anti-phase synchronization and beating phenomena is observed. A simple toy-model based on elementary hydrodynamics describes the observed oscillations and leads to oscillation frequencies in the right order of magnitude.
The kinetic Ising model in a weak oscillating magnetic field is studied in the context of stochas... more The kinetic Ising model in a weak oscillating magnetic field is studied in the context of stochastic resonance. The signal-to-noise ratio calculated with simulations is found to peak at a nontrivial resonance temperature above the equilibrium critical temperature T c. We argue that its appearance is closely related to the vanishing of the kinetic coefficient at T c. Comparisons with various theoretical results in one and higher dimensions are made. ͓S1063-651X͑99͒09103-5͔
Physica A: Statistical Mechanics and its Applications, 2003
We model the collective clapping of spectators by globally coupled two-mode stochastic oscillator... more We model the collective clapping of spectators by globally coupled two-mode stochastic oscillators. All distinct experimentally observable clapping modes are successfully reproduced. Surprisingly, it is found that in an extended region of the parameter space the periodicity of the collective output is strongly enhanced by the considered coupling. The model o ers a realistic way to generate periodic dynamics by coupling largely stochastic units.
Physica A: Statistical Mechanics and its Applications, 2005
A model based on first-degree family relations network is used to describe the wealth distributio... more A model based on first-degree family relations network is used to describe the wealth distribution in societies. The network structure is not a-priori introduced in the model, it is generated in parallel with the wealth values through simple and realistic dynamical rules. The model has two main parameters, governing the wealth exchange in the network. Choosing their values realistically, leads to wealth distributions in good agreement with measured data. The cumulative wealth distribution function has an exponential behavior in the low and medium wealth limit, and shows the Pareto-like power-law tail for the upper 5% of the society. The obtained Pareto indexes are in good agreement with the measured ones. The generated family networks also converges to a statistically stable topology with a simple Poissonian degree distribution. On this family-network many interesting correlations are studied, and the main factors leading to wealth-diversification and the formation of the Pareto law are identified.
... proposée. L'observateur permet de reconstruire l'état dynamique du véhicule... more ... proposée. L'observateur permet de reconstruire l'état dynamique du véhicule, puis fournit une estimation des forces latérales. Mots-clés Modélisation, Véhicule Poids Lourd, Observa-teur, Mode Glissant, Estimation, Force Latérale. ...
The ground-state of an infinite-range Potts glass-type model with ±J bonds and unrestricted numbe... more The ground-state of an infinite-range Potts glass-type model with ±J bonds and unrestricted number of states is used to investigate coalition formation. As a function of the q probability of +J bonds in the system it is found that the r relative size of the largest cluster (a cluster being the group of elements in the same state) shows a percolation like behavior. By a simple renormalization approach and several optimization methods we investigate the r(q) curves for finite systems sizes. Non-trivial consequences for social percolation problems are discussed. 87.23 Ge (Dynamics of social systems), 75.50.Lk (Spin glasses and other random magnets)
Evaporation of a small glass of ethylic alcohol is studied both experimentally and through an ele... more Evaporation of a small glass of ethylic alcohol is studied both experimentally and through an elementary thermal physics approach. For a cylindrical beaker and no air flow in the room, a simple quadratic relation is found between the evaporation time and the mass of evaporated liquid. This problem and the obtained results offer excellent possibilities for simple student experiments and for testing basic principles of thermal physics. As an example, we use the obtained results for estimating the value of the Boltzmann constant from evaporation experiments.
We reverse engineer entropy formulas from entropic divergence, optimized to given classes of prob... more We reverse engineer entropy formulas from entropic divergence, optimized to given classes of probability distribution function (PDF) evolution dynamical equation. For linear dynamics of the distribution function, the traditional Kullback–Leibler formula follows from using the logarithm function in the Csiszár’s f-divergence construction, while for nonlinear master equations more general formulas emerge. As applications, we review a local growth and global reset (LGGR) model for citation distributions, income distribution models and hadron number fluctuations in high energy collisions.
Using the Swendsen and Wang algorithm, high accuracy Monte Carlo simulations were performed to st... more Using the Swendsen and Wang algorithm, high accuracy Monte Carlo simulations were performed to study the concentration dependence of the Curie temperature in binary, ferromagnetic Ising systems on the simple-cubic lattice. Our results are in good agreement with known mean-field like approaches. Based on former theoretical formulas we propose a new way of estimating the Curie temperature of these systems.
The topology and dynamics of stripe-like magnetic domains obtained in a ferrimagnetic garnet subj... more The topology and dynamics of stripe-like magnetic domains obtained in a ferrimagnetic garnet subjected to a time-dependent external magnetic field is studied experimentally and theoretically. Experiments are performed on a commercially available magnetic bubble apparatus, allowing the observation of the time-evolution of the magnetic domain structure. The system is modeled by a meso-scale Ising-type lattice model. Exchange and dipolar interactions between the spins, and interaction of the spins with the external magnetic field are considered. The model is investigated by kinetic Monte Carlo simulations with time-varying transition rates. In the limit of low temperatures the elaborated model leads to a magnetic domain topology and dynamics that is similar to the ones observed in the experiments. In the highly non-equilibrium limit with a high driving frequency the model reproduces the experimentally recorded hysteresis loops as well.
Physica A: Statistical Mechanics and its Applications, 2007
The distribution of wealth in the Hungarian medieval aristocratic society is reported and studied... more The distribution of wealth in the Hungarian medieval aristocratic society is reported and studied. The number of serf families belonging to a noble is taken as a measure of the corresponding wealth. Our results reveal the power-law nature of this distribution function, confirming the validity of the Pareto law for such a society. The obtained Pareto index α = 0.92 is however smaller than the values currently reported in the literature. We argue that the value close to 1, of the Pareto index is a consequence of the absence of a relevant economic life in the targeted society, in agreement with the prediction of existing wealth distribution models for the idealized case of independently acting agents. Models developed to explain city populations may also be adapted to justify our results.
The dynamics of a spring-block train placed on a moving conveyor belt is investigated both by sim... more The dynamics of a spring-block train placed on a moving conveyor belt is investigated both by simple experiments and computer simulations. The first block is connected by spring to an external static point, and due to the dragging effect of the belt the blocks undergo complex stickslip dynamics. A qualitative agreement with the experimental results can only be achieved by taking into account the spatial inhomogeneity of the friction force on the belt's surface, modeled as noise. As a function of the velocity of the conveyor belt and the noise strength, the system exhibits complex, self-organized critical, sometimes chaotic dynamics and phase transition-like behavior. Noise induced chaos and intermittency is also observed. Simulations suggest that the maximum complexity of the dynamical states is achieved for a relatively small number of blocks, around five.
The phase-space of a simple synchronization model is thoroughly investigated. The model considers... more The phase-space of a simple synchronization model is thoroughly investigated. The model considers two-mode stochastic oscillators, coupled through a pulse-like interaction controlled by simple optimization rules. A complex phase space is uncovered as a function of two relevant model parameters that are related to the optimization threshold and the periods of the two oscillation modes. Several phases with different periodic global output signals are identified. It is shown that the system exhibits partial synchronization under unexpectedly general conditions.
Physica A: Statistical Mechanics and its Applications, 2007
This article was published in an Elsevier journal. The attached copy is furnished to the author f... more This article was published in an Elsevier journal. The attached copy is furnished to the author for non-commercial research and education use, including for instruction at the author's institution, sharing with colleagues and providing to institution administration. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit:
We consider two external laser beams interfering inside a n-GaAs with a nonlinear feedback. In a ... more We consider two external laser beams interfering inside a n-GaAs with a nonlinear feedback. In a given parameter region coexistence of the two unstable periodic domain trains (UPDTs) is found in this system. The UPDT is associated with the formation of intermittent oscillating current in the circuit. By external periodic driving, a novel resonance is observed in both inside one UPDT and the switching between the two UPDTs. The signal-to-noise ratio (SNR) as a function of driving amplitude A is numericaly investigated and the nonmonotonic behavior of the SNR(A) spectrum is observed.
Modelling and Simulation in Materials Science and Engineering, 1997
A new Monte Carlo method is described for studying the equilibrium shapes of fluids on solid surf... more A new Monte Carlo method is described for studying the equilibrium shapes of fluids on solid surfaces when the contact angles on the surface are smaller or equal to π/2. The method minimizes the energy of the system by consecutively applying two distinct annealing mechanisms. The method is tested for some simple analytically solvable cases and, as an example, applied to a more complex geometry.
The average travelling speed increases in a nontrivial manner with the travel distance. This lead... more The average travelling speed increases in a nontrivial manner with the travel distance. This leads to scaling-like relations on quite extended spatial scales, for all mobility modes taken together and also for a given mobility mode in part. We offer a wide range of experimental results, investigating and quantifying this universal effect and its measurable causes. The increasing travelling speed with the travel distance arises from the combined effects of: choosing the most appropriate travelling mode; the structure of the travel networks; the travel times lost in the main hubs, starting or target cities; and the speed limit of roads and vehicles.
Spontaneous synchronization of an ensemble of metronomes placed on a freely rotating platform is ... more Spontaneous synchronization of an ensemble of metronomes placed on a freely rotating platform is studied experimentally and by computer simulations. A striking in-phase synchronization is observed when the metronomes' beat frequencies are fixed above a critical limit. Increasing the number of metronomes placed on the disk leads to an observable decrease in the level of the emerging synchronization. A realistic model with experimentally determined parameters is considered in order to understand the observed results. The conditions favoring the emergence of synchronization are investigated. It is shown that the experimentally observed trends can be reproduced by assuming a finite spread in the metronomes' natural frequencies. In the limit of large numbers of metronomes, we show that synchronization emerges only above a critical beat frequency value.
Oscillation and collective behavior in convection-driven fluid columns are investigated and discu... more Oscillation and collective behavior in convection-driven fluid columns are investigated and discussed in analogy with similar phenomenon observed for the flickering flames of candle bundles. It is shown experimentally that an ascending circular Helium gas column performs an oscillation which is similar in several aspects to the oscillation of diffusion flames. Increasing the nozzle diameter leads to a decrease in the oscillation frequency, while increasing the flow rate results in an increase in this frequency. For helium columns oscillating at nearby frequency and placed close to each other anti-phase synchronization and beating phenomena is observed. A simple toy-model based on elementary hydrodynamics describes the observed oscillations and leads to oscillation frequencies in the right order of magnitude.
The kinetic Ising model in a weak oscillating magnetic field is studied in the context of stochas... more The kinetic Ising model in a weak oscillating magnetic field is studied in the context of stochastic resonance. The signal-to-noise ratio calculated with simulations is found to peak at a nontrivial resonance temperature above the equilibrium critical temperature T c. We argue that its appearance is closely related to the vanishing of the kinetic coefficient at T c. Comparisons with various theoretical results in one and higher dimensions are made. ͓S1063-651X͑99͒09103-5͔
Physica A: Statistical Mechanics and its Applications, 2003
We model the collective clapping of spectators by globally coupled two-mode stochastic oscillator... more We model the collective clapping of spectators by globally coupled two-mode stochastic oscillators. All distinct experimentally observable clapping modes are successfully reproduced. Surprisingly, it is found that in an extended region of the parameter space the periodicity of the collective output is strongly enhanced by the considered coupling. The model o ers a realistic way to generate periodic dynamics by coupling largely stochastic units.
Physica A: Statistical Mechanics and its Applications, 2005
A model based on first-degree family relations network is used to describe the wealth distributio... more A model based on first-degree family relations network is used to describe the wealth distribution in societies. The network structure is not a-priori introduced in the model, it is generated in parallel with the wealth values through simple and realistic dynamical rules. The model has two main parameters, governing the wealth exchange in the network. Choosing their values realistically, leads to wealth distributions in good agreement with measured data. The cumulative wealth distribution function has an exponential behavior in the low and medium wealth limit, and shows the Pareto-like power-law tail for the upper 5% of the society. The obtained Pareto indexes are in good agreement with the measured ones. The generated family networks also converges to a statistically stable topology with a simple Poissonian degree distribution. On this family-network many interesting correlations are studied, and the main factors leading to wealth-diversification and the formation of the Pareto law are identified.
... proposée. L'observateur permet de reconstruire l'état dynamique du véhicule... more ... proposée. L'observateur permet de reconstruire l'état dynamique du véhicule, puis fournit une estimation des forces latérales. Mots-clés Modélisation, Véhicule Poids Lourd, Observa-teur, Mode Glissant, Estimation, Force Latérale. ...
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