Chaotic Set Research Articles

Rough basin boundaries in high dimension: Can we classify them experimentally?

We show that a known condition for having rough basin boundaries in bistable 2D maps holds for high-dimensional bistable systems that possess a unique nonattracting chaotic set embedded in their basin boundaries. The condition for roughness is that the cross-boundary Lyapunov exponent λx on the nonattracting set is not the maximal one. Furthermore, we provide a formula for the generally noninteger co-dimension of the rough basin boundary, which can be viewed as a generalization of the Kantz-Grassberger formula. This co-dimension that can be at most unity can be thought of as a partial co-dimension, and, so, it can be matched with a Lyapunov exponent. We show in 2D noninvertible- and 3D invertible-minimal models, that, formally, it cannot be matched with λx. Rather, the partial dimension D0 (x) that λx is associated with in the case of rough boundaries is trivially unity. Further results hint that the latter holds also in higher dimensions. This is a peculiar feature of rough fractals. Yet, D0 (x) cannot be measured via the uncertainty exponent along a line that traverses the boundary. Consequently, one cannot determine whether the boundary is a rough or a filamentary fractal by measuring fractal dimensions. Instead, one needs to measure both the maximal and cross-boundary Lyapunov exponents numerically or experimentally.

Chaotic Saddles in a Generalized Lorenz Model of Magnetoconvection

The nonlinear dynamics of a recently derived generalized Lorenz model [ Macek & Strumik, 2010 ] of magnetoconvection is studied. A bifurcation diagram is constructed as a function of the Rayleigh number where attractors and nonattracting chaotic sets coexist inside a periodic window. The nonattracting chaotic sets, also called chaotic saddles, are responsible for fractal basin boundaries with a fractal dimension near the dimension of the phase space, which causes the presence of very long chaotic transients. It is shown that the chaotic saddles can be used to infer properties of chaotic attractors outside the periodic window, such as their maximum Lyapunov exponent.

Complexity and chaos control in a discrete-time Lotka–Volterra predator–prey system

ABSTRACT In this paper, we investigate a discrete-time Lotka–Volterra predator–prey model that can undergo flip bifurcations and Hopf bifurcations by using the centre manifold theorem and bifurcation theory. Bifurcation diagrams, maximum Lyapunov exponents, and phase portraits verify the theoretical analysis, which exhibits complex dynamical behaviours such as period-7, 13, 14, 21, 27, 32 orbits, a cascade of period-doubling bifurcation in period-2, 4, 8, quasi-periodic orbits and the chaotic sets. Furthermore, the feedback control method is used to stabilize the chaotic orbits at an unstable fixed point. This result further reveals richer dynamics of the discrete model compared with the continuous model. It is found out that the appropriately carrying capacity can be helpful to stabilize the model. Instead, the higher or lower carrying capacity may destabilize the system producing more complex dynamical behaviours.

Global dynamic scenarios in a discrete-time model of renewable resource exploitation: a mathematical study

We consider the two-dimensional map introduced in Bischi et al. (J Differ Equ Appl 21(10):954–973, 2015) formulated as a model for a renewable resource exploitation process in an evolutionary setting. The global dynamic scenarios displayed by the model are not so often encountered in smooth two-dimensional dynamical systems. We explain the occurrence of such scenarios at the light of the theory of noninvertible maps. Moreover, complex structures of basins of attraction of coexisting invariant sets are observed. We analyze such structures by examining stability properties of chaotic sets, in the case in which a non-topological Milnor attractor is present. Stability changes of a chaotic set occur through global bifurcations (such as riddling and blowout) and are detected by means of the study of the spectrum of Lyapunov exponents associated with the set.

New technique to quantify chaotic dynamics based on differences between semi-implicit integration schemes

Many novel chaotic systems have recently been identified and numerically studied. Parametric chaotic sets are a valuable tool for determining and classifying oscillation regimes observed in nonlinear systems. Thus, efficient algorithms for the construction of parametric chaotic sets are of interest. This paper discusses the performance of algorithms used for plotting parametric chaotic sets, considering the chaotic Rossler, Newton-Leipnik and Marioka-Shimizu systems as examples. In this study, we compared four different approaches: calculation of largest Lyapunov exponents, statistical analysis of bifurcation diagrams, recurrence plots estimation and introduced the new analysis method based on differences between a couple of numerical models obtained by semi-implicit methods. The proposed technique allows one to distinguish the chaotic and periodic motion in nonlinear systems and does not require any additional procedures such as solutions normalization or the choice of initial divergence value which is certainly its advantage. We evaluated the performance of the algorithms with the two-stage approach. At the first stage, the required simulation time was estimated using the perceptual hash calculation. At the second stage, we examined the performance of the algorithms for plotting parametric chaotic sets with various resolutions. We explicitly demonstrated that the proposed algorithm has the best performance among all considered methods. Its implementation in the simulation and analysis software can speed up the calculations when obtaining high-resolution multi-parametric chaotic sets for complex nonlinear systems.

Mean Li-Yorke chaotic set along polynomial sequence with full Hausdorff dimension for \beta -transformation

<p style='text-indent:20px;'>We construct a mean Li-Yorke chaotic set along polynomial sequences (the degree of this polynomial is not less than three) with full Hausdorff dimension and full topological entropy for <inline-formula><tex-math id="M2">\begin{document}$ \beta $\end{document}</tex-math></inline-formula>-transformation. An uncountable subset <inline-formula><tex-math id="M3">\begin{document}$ C $\end{document}</tex-math></inline-formula> is said to be a mean Li-Yorke chaotic set along sequence <inline-formula><tex-math id="M4">\begin{document}$ \{a_n\} $\end{document}</tex-math></inline-formula>, if both <p style='text-indent:20px;'><disp-formula> <label/> <tex-math id="FE1"> \begin{document}$ \begin{equation*} \liminf\limits_{N\to \infty}\frac{1}{N}\sum\limits_{j = 1}^{N}d(f^{a_j}(x),f^{a_j}(y )) = 0 \text{ and } \limsup\limits_{N\to \infty}\frac{1}{N}\sum\limits_{j = 1}^{N}d(f^{a_j}(x),f^{a_j}(y ))&gt;0 \end{equation*} $\end{document} </tex-math></disp-formula> <p style='text-indent:20px;'>hold for any two distinct points <inline-formula><tex-math id="M5">\begin{document}$ x $\end{document}</tex-math></inline-formula> and <inline-formula><tex-math id="M6">\begin{document}$ y $\end{document}</tex-math></inline-formula> in <inline-formula><tex-math id="M7">\begin{document}$ C $\end{document}</tex-math></inline-formula>.

Machine-learning construction of a model for a macroscopic fluid variable using the delay-coordinate of a scalar observable

We construct a data-driven dynamical system model for a macroscopic variable the Reynolds number of a high-dimensionally chaotic fluid flow by training its scalar time-series data. We use a machine-learning approach, the reservoir computing for the construction of the model, and do not use the knowledge of a physical process of fluid dynamics in its procedure. It is confirmed that an inferred time-series obtained from the model approximates the actual one in each of various time-intervals, and that some characteristics of the chaotic invariant set mimic the actual ones. We investigate the appropriate choice of the delay-coordinate, especially the delay-time and the dimension, which enables us to construct a model having a relatively high-dimensional attractor easily.

An Extension of Discrete Lagrangian Descriptors for Unbounded Maps

In this paper, we provide an extension for the method of Discrete Lagrangian Descriptors with the purpose of exploring the phase space of unbounded maps. The key idea is to construct a working definition, that is built on the original approach introduced in [ Lopesino et al., 2015a ], and which relies on stopping the iteration of initial conditions when their orbits leave a certain region in the plane. This criterion is partly inspired by the classical analysis used in Dynamical Systems Theory to study the dynamics of maps by means of escape time plots. We illustrate the capability of this technique to reveal the geometrical template of stable and unstable invariant manifolds in phase space, and also the intricate structure of chaotic sets and strange attractors, by applying it to unveil the phase space of a well-known discrete-time system, the Hénon map.

Strange attractors and wandering domains near a homoclinic cycle to a bifocus

In this paper, we explore the three-dimensional chaotic set near a homoclinic cycle to a hyperbolic bifocus at which the vector field has negative divergence. If the invariant manifolds of the bifocus satisfy a non-degeneracy condition, a sequence of hyperbolic suspended horseshoes arises near the cycle, with one expanding and two contracting directions. We extend previous results on the field and we show that the first return map to a given cross section may be approximated by a map exhibiting heteroclinic tangencies associated to two periodic orbits. Under an additional hypothesis about the coexistence of two heteroclinically related periodic points (one without dominated splitting into one-dimensional sub-bundles), the heteroclinic tangencies can be slightly modified in order to satisfy Tatjer's conditions for a generalized tangency of codimension two. This configuration may be seen as the organizing center, by which one can obtain Bogdanov-Takens bifurcations and therefore, strange attractors, infinitely many sinks and non-trivial contracting wandering domains.

Bernoulli Mapping with Holeanda Saddle-Node Scenario of the Birth of Hyperbolic Smale–Williams Attractor

One-dimensional Bernoulli mapping with hole is suggested to describe the regularities of the appearance of a chaotic set under the saddle-node scenario of the birth of the Smale–Williams hyperbolic attractor. In such a mapping, a non-trivial chaotic set (with non-zero Hausdorff dimension) arises in the general case as a result of a cascade of period-adding bifurcations characterized by geometric scaling both in the phase space and in the parameter space. Numerical analysis of the behavior of models demonstrating the saddle-node scenario of birth of a hyperbolic chaotic Smale–Williams attractor shows that these regularities are preserved in the case of multidimensional systems. Limits of applicability of the approximate 1D model are discussed.

Analysis of multistability, hidden chaos and transient chaos in brushless DC motor

Abstract The dynamics of brushless DC motor (BLDCM), a type of permanent magnet synchronous motor (PMSM) is investigated. The dynamical model of the BLDCM is compared to a mostly used model of PMSM. The BLDCM transition to chaos is briefly investigated both on the local level through local bifurcations and global level through manifold and invariant sets. All the transition parameter values are given. Apart from transition, multistability of the BLDCM is observed and assessed with stability basin. For some parameter values all dynamic modes (stable fixed point, limit cycle, chaotic attractor) coexist. For other parameter values multistability concerns different stable equilibria. Also, hidden chaos which is of non-Shilnikov type is examined and reported in BLDCM with the method of homotopy. Hidden chaos is defined from the basin of attraction. Transient features of the hidden chaotic set are studied. Finally, transient time of hidden chaos improves with two methods: critical velocity (acceleration) surfaces and Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm.

Li-Yorke chaotic eigen set of the backward shift operator on ℓ2(𝕅)

Abstract In this paper, we prove our main result that the Li-Yorke chaotic eigen set of a positive integer multiple of the backward shift operator on ℓ2 (𝕅) is a disk in the complex plane 𝔺 and the union of such Li-Yorke chaotic eigen set’s is the whole complex plane 𝔺.

Экономические макрорегионы: интеграционный феномен или политико-географическая целесообразность? Случай Дальнего Востока

The dividing of Russian economic space into macroregions is presented in Strategy of Spatial Development of Russian Federation as a key fragment of the policy mobilizing the spatial factor of national economic development. The article considers the general problem of economic zoning as a means of formalizing the structure of the national economic space, the allocation of interacting territorial fragments within its borders. It is shown that in the presence of canonical solutions to the problem of spatial breakdown at the theoretical level (for example, W. Christaller hexagons), there is no empirical solution common for all types of spaces and for all time periods. It is noted that in Russia, the USSR and the Russian Federation the task of determining the optimal network of economic regions has always been and still remains a key one as is stressed in the recently endorsed the Strategy. Its content has a fundamental peculiarity both due to a large scale of the geographical space concerned, its exceptional heterogeneity and a high degree of polarization of the economic space. We are speaking about the multi-level economic zoning where a special position in the system of economic regions is vested with macroregions. The authors consider the criteria for allocating large economic regions and analyze the validity of recognizing 12 macroregions in the Far Eastern Economic Macroregion according to Strategy formed by the administrative inclusion of the Zabaikalsky Krai and the Republic of Buryatia in the Far Eastern Federal District. The article analyzes the theoretical and empirical foundations of the new macroeconomic zoning. Particular emphasis is laid on determining the configuration of market zones of the Russian Federation constituent entities. It is shown that neither the former macroregion under the Far Eastern Federal District nor the one formed in November 2018 meets the economic criteria for breaking down the economic space, as they represent a more chaotic set of multidirectional market zones rather than a relatively homogenous economic landscape

Flip bifurcation and Neimark–Sacker bifurcation in a discrete predator–prey model with harvesting

In this paper, a difference-algebraic predator–prey model is proposed, and its complex dynamical behaviors are analyzed. The model is a discrete singular system, which is obtained by using Euler scheme to discretize a differential-algebraic predator–prey model with harvesting that we establish. Firstly, the local stability of the interior equilibrium point of proposed model is investigated on the basis of discrete dynamical system theory. Further, by applying the new normal form of difference-algebraic equations, center manifold theory and bifurcation theory, the Flip bifurcation and Neimark–Sacker bifurcation around the interior equilibrium point are studied, where the step size is treated as the variable bifurcation parameter. Lastly, with the help of Matlab software, some numerical simulations are performed not only to validate our theoretical results, but also to show the abundant dynamical behaviors, such as period-doubling bifurcations, period 2, 4, 8, and 16 orbits, invariant closed curve, and chaotic sets. In particular, the corresponding maximum Lyapunov exponents are numerically calculated to corroborate the bifurcation and chaotic behaviors.

Аппроксимация множеств прямых на плоскости

A few general lines in the ordinary Euclidean plane are said to be line generators of a plane linear set. To be able to say that every line of the set belongs to one-parametrical line set we have to find their envelope. We thus create a pencil of lines. In this article it will be shown that there are a finite number of pencils in one linear set. To find a pencil of lines the linear parametrical approximation is applied. Almost all of problems concerning the parametrical approximation of figure sets are well known and deeply developed for any point sets. The problem of approximation for non-point sets is an actual one. The aim of this paper is to give a path to parametrical approximation of linear sets defined in plane. The sets are discrete and consist of finite number of lines without any order. Each line of the set is given as y = ax + b. Parametrical approximation means a transformation the discrete set of lines into completely continuous family of lines. There are some problems. 1. The problem of order. It is necessary to represent the chaotic set of lines as well-ordered one. The problem is solved by means of directed circuits. Any of chaotic sets has a finite number of directed circuits. To create an order means to find all directed circuits in the given set. 2. The problem of choice. In order to find the best approximation, for example, the simplest one it is necessary to choose the simplest circuit. Some criteria of the choice are discussed in the paper. 3. Interpolation the set of line factors. A direct approach would simply construct an interpolation for all line factors. But this can lead to undesirable oscillations of the line family. To eliminate the oscillations the special factor interpolation are suggested. There are linear sets having one or several multiple points, one or several multiple lines and various combinations of multiple points and lines. Some theorems applied to these cases are formulated in the paper.

Dynamics and chaos control in a discrete-time ratio-dependent Holling-Tanner model

A discrete-time Holling-Tanner model with ratio-dependent functional response is examined. We show that the system experiences a flip bifurcation and Neimark-Sacker bifurcation or both together at positive fixed point in the interior of mathbb {R}^{2}_{+} when one of the model parameter crosses its threshold value. We concentrate our attention to determine the existence conditions and direction of bifurcations via center manifold theory. To validate analytical results, numerical simulations are employed which include bifurcations, phase portraits, stable orbits, invariant closed circle, and attracting chaotic sets. In addition, the existence of chaos in the system is justified numerically by the sign of maximum Lyapunov exponents and fractal dimension. Finally, we control chaotic trajectories exists in the system by feedback control strategy.

State-dependent vulnerability of synchronization.

A state-dependent vulnerability of synchronization is shown to exist in a complex network composed of numerically simulated electronic circuits. We demonstrate that disturbances to the local dynamics of network units can produce different outcomes to synchronization depending on the current state of its trajectory. We address such state dependence by systematically perturbing the synchronized system at states equally distributed along its trajectory. We find the states at which the perturbation desynchronizes the network to be complicatedly mixed with the ones that restore synchronization. Additionally, we characterize perturbation sets obtained for consecutive states by defining a safety index between them. Finally, we demonstrate that the observed vulnerability is due to the existence of an unstable chaotic set in the system's state space.

Singular cycles connecting saddle periodic orbit and saddle equilibrium in piecewise smooth systems

For flows, the singular cycles connecting saddle periodic orbit and saddle equilibrium can poten- tially result in the so-called singular horseshoe, which means the existence of a non-uniformly hyperbolic chaotic invariant set. However, it is very hard to find a specific dynamical system that exhibits such singular cycles in general. In this paper, the existence of the singular cycles involved in saddle periodic orbits is studied by two types of piecewise affine systems: one is the piecewise affine system having an admissible saddle point with only real eigenvalues and an admissible saddle periodic orbit, and the other is the piecewise affine system having an admissible saddle- focus and an admissible saddle periodic orbit. Precisely, several kinds of sufficient conditions are obtained for the existence of only one heteroclinic cycle or only two heteroclinic cycles in the two types of piecewise affine systems, respectively. In addition, some examples are presented to illustrate the results.

Dynamics analysis for a discrete dynamic competition model

In this paper, the dynamics of a discrete market share attraction model are investigated. It shows that the system can undergo flip bifurcation and chaos. The stability and bifurcation of a market share attraction model are analyzed by using the bifurcation theory and the center manifold theorem. The system displays complex dynamical behaviors, including period-1, 2, 4, 6, 8, 16 orbits, invariant cycle, a cascade of period-doubling, quasi-periodic orbits, and the chaotic sets. Numerical simulations illustrate the analysis and results.

Transport in Hamiltonian systems with slowly changing phase space structure

Transport in Hamiltonian systems with weak chaotic perturbations has been much studied in the past. In this paper, we introduce a new class of problems: transport in Hamiltonian systems with slowly changing phase space structure that are not order one perturbations of a given Hamiltonian. This class of problems is very important for many applications, for instance in celestial mechanics. As an example, we study a class of one-dimensional Hamiltonians that depend explicitly on time and on stochastic external parameters. The variations of the external parameters are responsible for a distortion of the phase space structures: chaotic, weakly chaotic and regular sets change with time. We show that theoretical predictions of transport rates can be made in the limit where the variations of the stochastic parameters are very slow compared to the Hamiltonian dynamics. Exact asymptotic results can be obtained in the one-dimensional case where the Hamiltonian dynamics is integrable for fixed values of the parameters. For the more interesting chaotic Hamiltonian dynamics case, we show that two mechanisms contribute to the transport. For some range of the parameter variations, one mechanism -called ”transport by migration with the mixing regions” - is dominant. We are then able to model transport in phase space by a Markov model, the local diffusion model, and to give reasonably good transport estimates.