Stellar diffusion in barred spiral galaxies
  We characterize empirically the radial diffusion of stars in the plane of a
typical barred disk galaxy by calculating the local spatial diffusion
coefficient and diffusion time-scale for bulge-disk-halo N-body self-consistent
systems which initially differ in the Safronov-Toomre-Q_T parameter. We find
different diffusion scenarios that depend on the bar strength and on the degree
of instability of the disk. Marginally stable disks, with Q_T \sim 1, have two
families of bar orbits with different values of angular momentum and energy,
which determine a large diffusion in the corotation region. In hot disks, Q_T>
1, stellar diffusion is reduced with respect to the case of marginally stable
disks. In cold models, we find that spatial diffusion is not constant in time
and strongly depends on the activity of the bar, which can move stars all over
the disk recurrently. We conclude that to realistically study the impact of
radial migration on the chemical evolution modeling of the Milky Way the role
of the bar has to be taken into account.
