How does the mass transport in disk galaxy models influence the
  character of orbits?
  We explore the regular or chaotic nature of orbits of stars moving in the
meridional (R,z) plane of an axially symmetric time-dependent disk galaxy model
with a central, spherically symmetric nucleus. In particular, mass is linearly
transported from the disk to the galactic nucleus, in order to mimic, in a way,
the case of self-consistent interactions of an actual N-body simulation. We
thus try to unveil the influence of this mass transportation on the different
families of orbits of stars by monitoring how the percentage of chaotic orbits,
as well as the percentages of orbits of the main regular resonant families,
evolve as the galaxy develops a dense and massive nucleus in its core. The SALI
method is applied to samples of orbits in order to distinguish safely between
ordered and chaotic motion. In addition, a method based on the concept of
spectral dynamics is used for identifying the various families of regular
orbits and also for recognizing the secondary resonances that bifurcate from
them. Our computations strongly suggest that the amount of the observed chaos
is substantially increased as the nucleus becomes more massive. Furthermore,
extensive numerical calculations indicate that there are orbits which change
their nature from regular to chaotic and vice versa and also orbits which
maintain their orbital character during the galactic evolution. The present
outcomes are compared to earlier related work.
