Examining the Chaotic Behavior in Dynamical Systems by Means of the 0-1 Test

We perform the stability analysis and we study the chaotic behavior of dynamical systems, which depict the 3-particle Toda lattice truncations through the lens of the 0-1 test, proposed by Gottwald and Melbourne. We prove that the new test applies successfully and with good accuracy in most of the cases we investigated. We perform some comparisons of the well-known maximum Lyapunov characteristic number method with the 0-1 method, and we claim that 0-1 test can be subsidiary to the LCN method. The 0-1 test is a very efficient method for studying highly chaotic Hamiltonian systems of the kind we study in our paper and is particularly useful in characterizing the transition from regularity to chaos.

A REVIEW STUDY OF THE 3-PARTICLE TODA LATTICE AND HIGHER ORDER TRUNCATIONS: THE EVEN-ORDER CASES — PART II

We complete the study of the numerical behavior of the truncated 3-particle Toda lattice (3pTL) with even truncations at orders n = 2k, k = 2, …, 10. We use (as in Part I): (a) the method of Poincaré surface of section, (b) the maximum Lyapunov characteristic number and (c) the ratio of the families of ordered periodic orbits. We derived some similarities and quite many differences between the odd and even order expansions.

A REVIEW STUDY OF THE 3-PARTICLE TODA LATTICE AND HIGHER-ORDER TRUNCATIONS: THE ODD-ORDER CASES — PART I

The numerical behavior of the truncated 3-particle Toda lattice (3pTL) is reviewed and studied in more detail (than in previous papers) and at higher energies (at odd-orders n ≤ 9). We further extended our study to higher truncations at odd-orders, n = 2k + 1, k = 1, …, 9. We have located the majority of the families of periodic orbits along with their main bifurcations. By using: (a) the method of Poincaré surface of section, (b) the maximum Lyapunov characteristic number and (c) the ratio of the families of ordered periodic orbits, we studied the topology of the nine odd-order Hamiltonians with respect to their order of truncation.

Conditional Entropy: A Tool to Explore the Phase Space

In this paper we show that the Conditional Entropy of nearby orbits may be a useful tool to explore the phase space associated to a given Hamiltonian. The arc length parameter along the orbits, instead of the time, is used as a random variable to compute the entropy. In the first part of this work we summarise the main analytical results to support this tool while, in the second part, we present numerical evidence that this technique is able to localise (stable) periodic and quasiperiodic orbits, ‘aperiodic’ orbits (chaotic motion) and unstable periodic orbits (the ‘source’ of chaotic motion). Besides, we show that this technique provides a measure of chaos which is similar to that given by the largest Lyapunov Characteristic Number. It is important to remark that this method is very simple to compute and does not require long time integrations, just realistic physical times.

Detection of Ordered and Chaotic Motion using The Dynamical Spectra

Two simple and efficient numerical methods to explore the phase space structure are presented, based on the properties of the “dynamical spectra”. 1) We calculate a “spectral distance”Dof the dynamical spectra for two different initial deviation vectors.D→ 0 in the case of chaotic orbits, whileD→const≠ 0 in the case of ordered orbits. This method is by orders of magnitude faster than the method of the Lyapunov Characteristic Number (LCN). 2) We define a sensitive indicator called ROTOR (ROtational TOri Recongnizer) for 2D maps. The ROTOR remains zero in time on a rotational torus, while it tends to infinity at a rate ∝N= number of iterations, in any case other than a rotational torus. We use this method to locate the last KAM torus of an island of stability, as well as the most important cantori causing stickiness near it.

The Role of Chaos in Barred Galaxies

Ordered orbits in barred galaxies appear along the bar and between the −4/1 and −2/1 resonances of the outer spiral. Chaotic orbits appear mainly near corotation. Such orbits support the bar and the spiral for long times and they are important for self-consistency. There are three main mechanisms for transition from order to chaos: (a) infinite bifurcations, (b) infinite gaps, and (c) infinite spirals. The Lyapunov characteristic number is zero for ordered orbits and positive for chaotic orbits. But much more information is provided by the distribution of the stretching numbers (one-period Lyapunov characteristic numbers). The spectrum of stretching numbers is invariant with respect to initial conditions in a connected chaotic domain. We provide examples of such spectra for 2-D maps, plane galactic orbits, 2-D dissipative systems, 3-D systems (represented by 4-D maps), and systems depending periodically on the time.