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1
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Stochastic Resonance in System with On-Off Intermittency

100%
Krawiecki A.
Acta Physica Polonica A
|
1997
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vol. 92
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issue 6
1101-1108
EN
Stochastic resonance in a chaotic threshold-crossing system exhibiting on-off intermittency and attractor bubbling: the logistic map with the control parameter varying randomly or chaotically in time is studied in the case of weak additive and multiplicative periodic forcing. In both cases signal-to-noise ratio shows dependence on the forcing frequency; in the case of multiplicative forcing this dependence appears even for very small frequencies. It is shown that this is a result of a very long characteristic time scale, typical of systems with on-off intermittency.
2
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On-Off Intermittency in Randomly Driven Parallel Pumping

100%
Krawiecki A.
Acta Physica Polonica A
|
1997
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vol. 92
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issue 2
465-468
EN
A model of parallel pumping with many interacting parametric spin-wave pairs is investigated numerically. On-off intermittency is obtained in the time series of absorption when the rf field amplitude is varied randomly in time, slowly in comparison with the rf field frequency, and when its mean value exceeds slightly the parallel pumping instability threshold. If the interactions between parametrically and thermally excited spin waves are neglected, only one parametric spin-wave pair is strongly excited and exhibits intermittent behaviour. In the opposite case a packet of parametric spin waves with frequencies close to half the pumping frequency may be excited. This modifies quantitatively, but not qualitatively the intermittency characteristics in the presence of thermal noise.
3
Content available remote

Synchronization Among Spin-Wave Amplitudes in Chaotic Nonlinear Ferromagnetic Resonance

100%
Krawiecki A.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
947-950
EN
A model of chaos in high-power ferromagnetic resonance in coincidence regime, based on three-magnon interactions of the uniform mode with a group of pairs of parametric spin waves, is investigated numerically. The results are interpreted from the point of view of chaotic synchronization theory. If all spin waves are identical, all of them are excited above the first-order Suhl instability threshold and in the chaotic regime their amplitudes show marginal synchronization, i.e. they differ only by a multiplicative factor, constant in time. If spin waves have slightly different instability thresholds, only one or few of them are excited. In the latter case, addition of weak thermal noise changes the results qualitatively. For low rf field amplitude, but above the threshold for chaos, still only few spin-wave pairs are excited above the thermal level. For higher rf field amplitude all spin waves in the group are excited, and their amplitudes are not synchronized. These results suggest that low correlation dimension of chaotic attractors, observed often in nonlinear ferromagnetic resonance, can be connected with chaotic synchronization among spin-wave amplitudes, in particular just above the threshold for chaos.
4
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Monte Carlo Studies of the p-Spin Models οn Scale-Free Hypernetworks

100%
Krawiecki A.
Acta Physica Polonica A
|
2013
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vol. 123
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issue 3
564-566
EN
Results of Monte Carlo simulations of p-spin models on scale-free hypernetworks are presented. The hypernetworks are obtained using the preferential attachment algorithm, the spins are located in the nodes and the hyperedges connecting p nodes correspond to non-zero ferromagnetic interactions involving p spins. Such models show high degeneracy of the ground state: apart from the ferromagnetic state, depending on the parameters of the preferential attachment algorithm leading to different topologies of the obtained hypernetworks, there are several or even infinitely many disordered (glassy) states with the same energy. For various network topologies quantities such as the specific heat or magnetic susceptibility show maxima as functions of the temperature, which suggests the occurrence of the glassy or ferromagnetic phase transition. The models under study may serve as a starting point for modelling various forms of cooperation in social and economic sciences involving many-body rather than two-body interactions.
5
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Majority-Vote Model on Scale-Free Hypergraphs

64%
Gradowski T., Krawiecki A.
Acta Physica Polonica A
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2015
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vol. 127
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issue 3A
A-55-A-58
EN
Majority-vote models on scale-free hypergraphs are investigated by means of numerical simulations with different variants of system dynamics. Hypergraphs are generalisations of ordinary graphs in which higher order of social organisation is included by introducing hyperedges corresponding to social groups, connecting more than two nodes. In the models under study, opinions of agents (two-state spins) placed in nodes are updated according to a probabilistic rule with control parameter representing social noise. The probability of a single spin flip depends on the average opinion within only one social group (hyperedge) the agent belongs to. This introduces an intermediate level of social interactions, in contrast with the case of networks, where the opinion of an agent usually depends on the average opinion of all neighbours. In all cases under consideration a second-order phase transition to a state with an uniform opinion was found as a function of the social noise, with the critical value of the control parameter and the critical exponents depending on the hypergraph topology and details of the system dynamics (node or hyperedge update).
6
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Theory of Nonlinear Ferromagnetic Resonance in the Samples with Magnetostatic and Exchange Boundary Conditions Imposed

64%
Krawiecki A., Sukiennicki A.
Acta Physica Polonica A
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1993
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vol. 83
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issue 4
505-515
EN
General theory of nonlinear ferromagnetic resonance is presented for samples with the usual magnetostatic and exchange boundary conditions imposed at the sample surface. In such samples the Suhl instabilities and other nonlinear effects occur due to nonlinear interactions of magnetostatic or dipole-exchange modes. All relevant types of interactions are included in the Hamiltonian: with the pumping field, three- and four-mode ones. Analytic calculation of the Suhl thresholds in the three possible types of instabilities in perpendicular and parallel pumping is performed for the sample in the shape of a thin slab.
7
Content available remote

On-Off Intermittency in Randomly Driven Nonlinear Ferromagnetic Resonance

64%
Krawiecki A., Sukiennicki A.
Acta Physica Polonica A
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1996
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vol. 89
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issue 1
37-45
EN
Simple models of nonlinear ferromagnetic resonance are considered which describe perpendicular resonance and parallel pumping with the rf field amplitude changing randomly and chaotically in time. On-off intermittency is obtained from the numerical solution of the equations of motion for the spin-wave amplitudes when the mean value of the rf field amplitude exceeds the Suhl instability threshold. Possible experimental applications are discussed.
8
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Structural Stochastic Multiresonance in Hierarchical Networks

64%
Krawiecki A., Kaim M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2B
B-72-B-76
EN
Systems with a structure of hierarchical networks, consisting of simple units placed in the nodes and interacting along the edges of the network, are ubiquitous in the modern society and economy. In this paper the problem of signal detection and transmission in such systems in the presence of noise is analyzed from the point of view of stochastic resonance. As examples simple tree-like and more complex Ravasz-Barabási networks of interacting threshold elements are considered. It is shown that stochastic multiresonance is often observed, a phenomenon characterized by the presence of two or more maxima of the output signal-to-noise ratio as a function of the input noise intensity. The origin of the additional maxima, which occur for small noise intensities, can be related to the structure of the interactions, thus the observed phenomenon is an example of structural stochastic multiresonance.
9
Content available remote

On-Off Intermittency and Peculiar Properties of Attractors in a Simple Model of Chaos in Ferromagnetic Resonance

64%
Krawiecki A., Sukiennicki A.
Acta Physica Polonica A
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1995
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vol. 88
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issue 2
269-282
EN
Some non-trivial phenomena in chaos in ferromagnetic resonance above the first-order Suhl instability threshold are obtained numerically from a simple model of three interacting modes. They include sudden changes of the correlation dimension of the attractor and the largest Lyapunov exponent with the rise of the rf field amplitude. Numerical evidence is provided that these effects may result from the on-off intermittency in the system of interacting modes. These results are qualitatively similar to the experimental ones, known from the literature, obtained for in-plane magnetized thin films.
10
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Content available

Chaotic Dynamics of a Linear Chain of Periodically Stimulated Neurons with Random Synaptic Connections

51%
Kosiński R., Krawiecki A., Sukiennicki A.
Acta Physica Polonica A
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2001
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vol. 100
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issue 1
89-99
EN
Dynamics of a neural network in the form of a linear chain of artificial neurons S_i∈(-1,1) influenced by an external sinusoidal stimulation is investigated as a function of the range k of synaptic connections with random values. Time evolution of the network is periodic for small k, however, clusters of neurons oscillating with a triple period of external stimulation, with quasiperiodic or with chaotic time evolution may occur. For increasing k the number and width of the chaotic clusters increase and for k >4 the chaotic motion occurs in the whole network. A route to chaos in the considered system is discussed.
11
Content available remote

Majority Vote Model on Multiplex Networks

51%
Krawiecki A., Gradowski T., Siudem G.
Acta Physica Polonica A
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2018
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vol. 133
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issue 6
1433-1440
EN
Majority vote model on multiplex networks with two independently generated layers in the form of scale-free networks is investigated by means of Monte Carlo simulations and heterogeneous mean-field approximation. In a version of the model under study each agent with probability 1-q (0≤q≤1/2) follows the opinions of the majorities of her neighbors within both layers if these opinions are identical; otherwise, she makes decision randomly. The model exhibits second-order ferromagnetic transition as q, the parameter measuring the level of internal noise, is decreased, with critical exponents depending on the details of the degree distributions in the layers. The critical value q_{c} of the parameter q evaluated in the heterogeneous mean-field approximation shows quantitative agreement with that obtained from numerical simulations for a broad range of parameters characterizing the degree distributions of the layers.
12
Content available remote

Simulations of Noise-Free Stochastic Resonance in Spin-Wave Chaos

51%
Krawiecki A., Reibold E., Benner H., Sukiennicki A.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
975-978
EN
Numerical simulations of noise-free stochastic resonance and aperiodic stochastic resonance in chaotic ferromagnetic resonance are presented. The model, based on three-magnon interactions between the externally excited uniform mode and pairs of spin waves, shows on-off intermittency. The rf magnetic field amplitude is slowly modulated by a small periodic or aperiodic signal, and the output signal, which reflects the occurrence of laminar phases and bursts in the time series of spin-wave amplitudes, is analyzed. On variation of the dc magnetic field the signal-to-noise ratio of the output signal and the correlation function between modulation and output signal pass a maximum, which indicates the occurrence of periodic and aperiodic stochastic resonance, respectively. The role of thermal magnon excitations in the occurrence of this maximum is clarified. The results are compared with experimental findings obtained in other types of intermittency.
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