2008, Vol.11, No.2, pp.265-268
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
Full text: Acrobat PDF (1181KB)
Copyright © Nonlinear Phenomena in Complex Systems. Last updated: July 10, 2008