Chaoticity in the vicinity of complex unstable periodic orbits in galactic type potentials

TL;DR

This study explores how weakly chaotic orbits near complex unstable periodic orbits in galactic potentials contribute to the formation and reinforcement of galactic structures like bulges and spiral arms.

Contribution

It demonstrates that orbits near complex unstable periodic orbits can support galactic features over significant time scales, expanding understanding of galactic morphology.

Findings

Weakly chaotic orbits reinforce galactic structures.

Phase space reshaping occurs near stability transitions.

Complex unstable orbits support observed galactic features.

Abstract

We investigate the evolution of phase space close to complex unstable periodic orbits in two galactic type potentials. They represent characteristic morphological types of disc galaxies, namely barred and normal (non-barred) spiral galaxies. These potentials are known for providing building blocks to support observed features such as the peanut, or X-shaped bulge, in the former case and the spiral arms in the latter. We investigate the possibility that these structures are reinforced, apart by regular orbits, also by orbits in the vicinity of complex unstable periodic orbits. We examine the evolution of the phase space structure in the immediate neighbourhood of the periodic orbits in cases where the stability of a family presents a successive transition from stability to complex instability and then to stability again, as energy increases. We find that we have a gradual reshaping of invariant structures close to the transition points and we trace this evolution in both models. We conclude that for time scales significant for the dynamics of galaxies, there are weakly chaotic orbits associated with complex unstable periodic orbits, which should be considered as structure-supporting, since they reinforce the morphological features we study.