NONLINEAR PHENOMENA IN COMPLEX SYSTEMS
An Interdisciplinary Journal

2008, Vol.11, No.2, pp.265-268


Does Chaotic Motion Support the Spiral Structure in Disk Galaxies?
P.A. Patsis

Spiral structure is observed in various different physical and biological systems. In astronomy it is encountered in disk galaxies, in accretion disks around black holes, in planetary rings, etc. However, spirals are ubiquitous in nature. They occur for instance in the well known Belousov-Zhabotinsky chemical reaction (see e.g. [1]) or in meteorological phenomena like the tropical cyclones. There is no unique dynamical mechanism explaining all of them. The physical processes that lead to spiral formation can be completely different from case to case. The present paper is about the spirals we encounter in disk galaxies, and discusses the possibility that different mechanisms may compete or collaborate for their formation even in the same physical system. We review briefly the work that has been done until now. This work points out that the spiral arms in some cases are build by regular orbits trapped around stable periodic orbits, in other cases their presence is the demonstration of the presence of Chaos on the disk and finally that there can be cases where both Order and Chaos shape the arms of a galaxy.
Key words: chaotic motion, spiral structure, galaxies

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