Nonlinear Phenomena in Complex Systems, 2020, Vol.23, No.2, pp.153

NONLINEAR PHENOMENA IN COMPLEX SYSTEMS
An Interdisciplinary Journal

2020, Vol.23, No.2, pp.153 - 164

On the Behavior of the Generalized Alignment Index (GALI) Method for Regular Motion in Multidimensional Hamiltonian Systems
H. T. Moges, Th. Manos, and Ch. Skokos

We investigate the behavior of the Generalized Alignment Index of order k (GALI_k) for regular orbits of multidimensional Hamiltonian systems. The GALI_k is an efficient chaos indicator, which asymptotically attains positive values for regular motion when 2≤k ≤N, with N being the dimension (D) of the torus on which the motion occurs. By considering several regular orbits in the neighborhood of two typical simple, stable periodic orbits of the Fermi-Pasta-Ulam-Tsingou (FPUT) β model for various values of the system's degrees of freedom, we show that the asymptotic GALI_k values decrease when the order k of the index increases and when the orbit's energy approaches the periodic orbit's destabilization energy where the stability island vanishes, while they increase when the considered regular orbit moves further away from the periodic one for a fixed energy. In addition, by performing extensive numerical simulations we show that the behavior of the index does not depend on the choice of the initial deviation vectors needed for its evaluation.

Key words: dynamical system, hamiltonian, generalized alignment index, periodic orbit

DOI: https://doi.org/10.33581/1561-4085-2020-23-2-153-164

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