Hyperbolic Invariant Sets Research Articles

Diffeomorphisms with infinitely many Smale horseshoes

ABSTRACT A class of planar diffeomorphims is formulated, with infinitely many coexisting Smale horseshoes, where the Lebesgue measure of the parameters with such strange dynamics is infinite. On each horseshoe, there exists a uniformly hyperbolic invariant set, on which the map is topologically conjugate to the two-sided full-shift on two symbols. Moreover, the topological entropy is infinite in certain parameter regions.

Review of Research on the Qualitative Theory of Differential Equations at St. Petersburg University. I. Stable Periodic Points of Diffeomorphisms with Homoclinic Points and Systems with Weakly Hyperbolic Invariant Sets

Review of Research on the Qualitative Theory of Differential Equations at St. Petersburg University. I. Stable Periodic Points of Diffeomorphisms with Homoclinic Points and Systems with Weakly Hyperbolic Invariant Sets

Review of the research on the qualitative theory of differential equations at St. Petersburg University. II. Locally qualitative analysis of essentially nonlinear systems

This article is the second one in a series of articles devoted to a review of the results of scientific research that have been carried out at the Department of Differential Equations of St.Petersburg University over the past three decades and continue to be carried out at the present time. The first article talked about studies of stable periodic points of diffeomorphisms with homoclinic points and systems of differential equations with weakly hyperbolic invariant sets. This paper presents the results of locally qualitative analysis of essentially nonlinear systems in the neighbourhood of the zero solution, obtained by employees and graduates of the department. A system is said to be essentially nonlinear if the Taylor series expansion of its right-hand sides does not contain linear terms. The study of such systems, firstly, is complicated by a more complex picture of the behavior of solutions compared to quasilinear systems. Secondly, there are not even theoretical formulas for the general solution of a nonlinear first-approximation system, the presence of which is so helpful in the quasi-linear case. All this complicates analysis and significantly limits technical capabilities. Therefore, almost any new results and any new methods of working with such systems are of great interest. One of the most effective tools for working with essentially nonlinear systems turned out to be the logarithmic Lozinsky norms. In a sense, they are an analogue of the characteristic exponents (eigenvalues) used in the theory of quasilinear systems. Research conducted at the department has demonstrated the wide possibilities of using logarithmic norms in a wide variety of problems.

Trajectories associated with parabolic and hyperbolic periodic points of piecewise linear area-preserving map

This paper investigates the characteristics of trajectories and invariant sets associated with parabolic and hyperbolic periodic points of a piecewise linear area-preserving map. When the fixed points in both partitions are parabolic, the trajectories may diverge or rotate repeatedly around the origin. By analyzing the trajectory motion in different regions of the phase plane, the characteristics of the trajectory repeated rotation around the origin are shown, and the trajectories may be either divergent or periodic. The necessary conditions for generating stable periodic orbits are presented. It is proved that there are forward invariant sets and that the trajectories from the invariant sets diverge in different quadrants and along a family of invariant lines parallel to the diagonal bisector of the quadrant. We reveal why there are island chains with invariant line segments in a chaotic sea. The method for determining invariant line segments is presented. For the map with two hyperbolic fixed points in both partitions, it is proved that there are forward invariant sets in the phase plane and all trajectories from the invariant sets diverge along a family of hyperbolic invariant sets.

Computer‐assisted analysis of chaos in a three‐species food chain model

AbstractIn this paper, a three‐species food chain model with Holling type IV and Beddington–DeAngelis functional responses is formulated. Numerical simulations show that this system can generate chaos for some parameter values. But the mechanism behind chaos is still unclear only through numerical simulations. Then, using the topological horseshoe theories and Conley–Moser conditions, we present a computer‐assisted analysis to show the chaoticity of this system in the topological sense, that is, it has positive topological entropy. We prove that the Poincaré map of this model possesses a closed uniformly hyperbolic chaotic invariant set, and it is topologically conjugate to a 2‐shift map. At last, we consider the impact of fear on this three‐species model. It is an important factor in controlling chaos in biological models, which has been validated in other models.

Rate-induced tipping: thresholds, edge states and connecting orbits

Rate-induced tipping (R-tipping) occurs when time-variation of input parameters of a dynamical system interacts with system timescales to give genuine nonautonomous instabilities. Such instabilities appear as the input varies at some critical rates and cannot, in general, be understood in terms of autonomous bifurcations in the frozen system with a fixed-in-time input. This paper develops an accessible mathematical framework for R-tipping in multidimensional nonautonomous dynamical systems with an autonomous future limit. We focus on R-tipping via loss of tracking of base attractors that are equilibria in the frozen system, due to crossing what we call regular R-tipping thresholds. These thresholds are anchored at infinity by regular R-tipping edge states: compact normally hyperbolic invariant sets of the autonomous future limit system that have one unstable direction, orientable stable manifold, and lie on a basin boundary. We define R-tipping and critical rates for the nonautonomous system in terms of special solutions that limit to a compact invariant set of the autonomous future limit system that is not an attractor. We focus on the case when the limit set is a regular edge state, introduce the concept of edge tails, and rigorously classify R-tipping into reversible, irreversible, and degenerate cases. The central idea is to use the autonomous dynamics of the future limit system to analyse R-tipping in the nonautonomous system. We compactify the original nonautonomous system to include the limiting autonomous dynamics. Considering regular R-tipping edge states that are equilibria allows us to prove two results. First, we give sufficient conditions for the occurrence of R-tipping in terms of easily testable properties of the frozen system and input variation. Second, we give necessary and sufficient conditions for the occurrence of reversible and irreversible R-tipping in terms of computationally verifiable (heteroclinic) connections to regular R-tipping edge states in the autonomous compactified system.

Boxing-in of a blender in a Hénon-like family

IntroductionThe extension of the Smale horseshoe construction for diffeomorphisms in the plane to those in spaces of at least dimension three may result in a hyperbolic invariant set referred to as a blender. The defining property of a blender is that it has a stable or unstable invariant manifold that appears to have a dimension larger than expected. In this study, we consider a Hénon-like family in ℝ3, which is the only explicitly given example of a system known to feature a blender in a certain range of a parameter (corresponding to an expansion or contraction rate). More specifically, as part of its hyperbolic set, this family has a pair of saddle fixed points with one-dimensional stable or unstable manifolds. When there is a blender, the closure of these manifolds cannot be avoided by one-dimensional curves coming from an appropriate direction. This property has been checked for the Hénon-like family by the method of computing extremely long pieces of global one-dimensional manifolds to determine the parameter range over which a blender exists.MethodsIn this study, we take the complimentary and local point of view of constructing an actual three-dimensional box (a parallelopiped) that acts as an outer cover of the hyperbolic set. The successive forward or backward images of this box form a nested sequence of sub-boxes that contains the hyperbolic set, as well as its respective local invariant manifold.ResultsThis constitutes a three-dimensional horseshoe that, in contrast to the idealized affine construction, is quite general and features sub-boxes with curved edges. The initial box is defined in a parameter-dependent way, and this allows us to characterize properties of the hyperbolic set intuitively.DiscussionIn particular, we trace relevant edges of sub-boxes as a function of the parameter to provide additional geometric insight into when the hyperbolic set may or may not be a blender.

Symplectomorphisms with positive metric entropy

We obtain a dichotomy for C 1 $C^1$ -generic symplectomorphisms: either all the Lyapunov exponents of almost every point vanish, or the map is partially hyperbolic and ergodic with respect to volume. This completes a program first put forth by Ricardo Mañé. A key ingredient is an analysis of partially hyperbolic sets of positive volume. We generalize to partially hyperbolic invariant sets the main result in Dolgopyat and Wilkinson (Astérisque 287 (2003), 33–60) that stable accessibility is C 1 $C^1$ -dense among partially hyperbolic diffeomorphisms.

The weak Smale horseshoe and mean hyperbolicity

The paper concerns the mean hyperbolicity of the skew-product flows induced by the perturbation equations driven by varieties of non-periodic forcings. The weakly averaged horseshoe can be constructed as a mean hyperbolic invariant set in the Poincare section for high dimensional phase space. Due to the non-periodic property, the Poincare return map restricted to the weakly averaged horseshoe region can semi-conjugate to the full Bernoulli shift on infinite symbols, which implies the infinitely many independent choices on the length of return time. As a direct application of mean hyperbolicity, we extend the shadowing lemma due to Liao to the general nonautonomous dynamical systems.

On Problems of Stability Theory for Weakly Hyperbolic Invariant Sets

This paper presents a brief survey for the theory of stability of weakly hyperbolic invariant sets. It has been proved in several papers that I published along with Pliss and Sell that a weakly hyperbolic invariant set is stable even if the Lipschitz condition fails to hold. However, the uniqueness of leaves of a weakly hyperbolic invariant set of a perturbed system remains an open question. We show that this problem is connected to the so-called plaque expansivity conjecture in the theory of dynamical systems.

On problems of the theory of stability of weakly hyperbolic invariant sets

On problems of the theory of stability of weakly hyperbolic invariant sets

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.

Shy shadows of infinite-dimensional partially hyperbolic invariant sets

Let${\mathcal{R}}$be a strongly compact$C^{2}$map defined in an open subset of an infinite-dimensional Banach space such that the image of its derivative$D_{F}{\mathcal{R}}$is dense for every $F$. Let$\unicode[STIX]{x1D6FA}$be a compact, forward invariant and partially hyperbolic set of${\mathcal{R}}$such that${\mathcal{R}}:\unicode[STIX]{x1D6FA}\rightarrow \unicode[STIX]{x1D6FA}$is onto. The$\unicode[STIX]{x1D6FF}$-shadow$W_{\unicode[STIX]{x1D6FF}}^{s}(\unicode[STIX]{x1D6FA})$of$\unicode[STIX]{x1D6FA}$is the union of the sets$$\begin{eqnarray}W_{\unicode[STIX]{x1D6FF}}^{s}(G)=\{F:\operatorname{dist}({\mathcal{R}}^{i}F,{\mathcal{R}}^{i}G)\leq \unicode[STIX]{x1D6FF}\text{for every }i\geq 0\},\end{eqnarray}$$where$G\in \unicode[STIX]{x1D6FA}$. Suppose that$W_{\unicode[STIX]{x1D6FF}}^{s}(\unicode[STIX]{x1D6FA})$has transversal empty interior, that is, for every$C^{1+\text{Lip}}$$n$-dimensional manifold$M$transversal to the distribution of dominated directions of$\unicode[STIX]{x1D6FA}$and sufficiently close to$W_{\unicode[STIX]{x1D6FF}}^{s}(\unicode[STIX]{x1D6FA})$we have that$M\cap W_{\unicode[STIX]{x1D6FF}}^{s}(\unicode[STIX]{x1D6FA})$has empty interior in$M$. Here$n$is the finite dimension of the strong unstable direction. We show that if$\unicode[STIX]{x1D6FF}^{\prime }$is small enough then$$\begin{eqnarray}\mathop{\bigcup }_{i\geq 0}{\mathcal{R}}^{-i}W_{\unicode[STIX]{x1D6FF}^{\prime }}^{s}(\unicode[STIX]{x1D6FA})\end{eqnarray}$$intercepts a$C^{k}$-generic finite-dimensional curve inside the Banach space in a set of parameters with zero Lebesgue measure for every$k\geq 0$. This extends to infinite-dimensional dynamical systems previous studies on the Lebesgue measure of stable laminations of invariants sets.

The Smale horseshoes in a class of non-invertible maps in with two-direction instability

We study the existence of Smale horseshoes of new type and the uniformly hyperbolic invariant sets for a class of non-invertible maps in three-dimensional Euclidean spaces with the dimension of instability equal to two. Parameter regions are given, for which the map has a horseshoe and a uniformly hyperbolic invariant set on which the map is topologically conjugate to the two-sided fullshift on four symbols.

On the stability of weakly hyperbolic invariant sets

The dynamical object which we study is a compact invariant set with a suitable hyperbolic structure. Stability of weakly hyperbolic sets was studied by V. A. Pliss and G. R. Sell (see [1,2]). They assumed that the neutral, unstable and stable linear spaces of the corresponding linearized systems satisfy Lipschitz condition. They showed that if a perturbation is small, then the perturbed system has a weakly hyperbolic set KY, which is homeomorphic to the weakly hyperbolic set K of the initial system, close to K, and the dynamics on KY is close to the dynamics on K. At the same time, it is known that the Lipschitz property is too strong in the sense that the set of systems without this property is generic. Hence, there was a need to introduce new methods of studying stability of weakly hyperbolic sets without Lipschitz condition. These new methods appeared in [16–20]. They were based on the local coordinates introduced in [18] and the continuous on the whole weakly hyperbolic set coordinates introduced in [19]. In this paper we will show that even without Lipschitz condition there exists a continuous mapping h such that h(K)=KY.

Topological horseshoe and its uniform hyperbolicity in the HP model.

A famous food-chain model proposed by Hastings and Powell is numerically restudied. The existence and uniform hyperbolicity of chaotic invariant sets are demonstrated by means of the topological horseshoe theory and the Conley-Moser conditions, indicating that, for a fixed cross section, the second return Poincaré map of the model possesses a closed uniformly hyperbolic chaotic invariant set, on which it is topologically conjugate to the 2-shift map.

Isolating blocks as computational tools in the circular restricted three-body problem

Isolating blocks may be used as computational tools to search for the invariant manifolds of orbits and hyperbolic invariant sets associated with libration points while also giving additional insight into the dynamics of the flow in these regions. We use isolating blocks to investigate the dynamics of objects entering the Earth–Moon system in the circular restricted three-body problem with energies close to the energy of the L2 libration point. Specifically, the stable and unstable manifolds of Lyapunov orbits and the hyperbolic invariant set around the libration points are obtained by numerically computing the way orbits exit from an isolating block in combination with a bisection method. Invariant spheres of solutions in the spatial problem may then be located using the resulting manifolds.

Chaotic Polynomial Maps

This paper introduces a class of polynomial maps in Euclidean spaces, investigates the conditions under which there exist Smale horseshoes and uniformly hyperbolic invariant sets, studies the chaotic dynamical behavior and strange attractors, and shows that some maps are chaotic in the sense of Li–Yorke or Devaney. This type of maps includes both the Logistic map and the Hénon map. For some diffeomorphisms with the expansion dimension equal to one or two in three-dimensional spaces, the conditions under which there exist Smale horseshoes and uniformly hyperbolic invariant sets on which the systems are topologically conjugate to the two-sided fullshift on finite alphabet are obtained; for some expanding maps, the chaotic region is analyzed by using the coupled-expansion theory and the Brouwer degree theory. For three types of higher-dimensional polynomial maps with degree two, the conditions under which there are Smale horseshoes and uniformly hyperbolic invariant sets are given, and the topological conjugacy between the maps on the invariant sets and the two-sided fullshift on finite alphabet is obtained. Some interesting maps with chaotic attractors and positive Lyapunov exponents in three-dimensional spaces are found by using computer simulations. In the end, two examples are provided to illustrate the theoretical results.

On the stability of hyperbolic attractors of systems of differential equations

We study small C 1-perturbations of systems of differential equations that have a weakly hyperbolic invariant set. We show that the weakly hyperbolic invariant set is stable even if the Lipschitz condition fails.

The anti-integrable limit

The anti-integrable limit is one of the convenient and relatively simple methods for the construction of chaotic hyperbolic invariant sets in Lagrangian, Hamiltonian, and other dynamical systems. This survey discusses the most natural context of the method, namely, discrete Lagrangian systems, and then presents examples and applications. Bibliography: 75 titles.