The inner cavity of the circumnuclear disc
  The circumnuclear disc (CND) orbiting the Galaxy's central black hole is a
reservoir of material that can ultimately provide energy through accretion, or
form stars in the presence of the black hole, as evidenced by the stellar
cluster that is presently located at the CND's centre. In this paper, we report
the results of a computational study of the dynamics of the CND. The results
lead us to question two paradigms that are prevalent in previous research on
the Galactic Centre. The first is that the disc's inner cavity is maintained by
the interaction of the central stellar cluster's strong winds with the disc's
inner rim, and second, that the presence of unstable clumps in the disc implies
that the CND is a transient feature. Our simulations show that, in the absence
of a magnetic field, the interaction of the wind with the inner disc rim
actually leads to a filling of the inner cavity within a few orbital
time-scales, contrary to previous expectations. However, including the effects
of magnetic fields stabilizes the inner disc rim against rapid inward
migration. Furthermore, this interaction causes instabilities that continuously
create clumps that are individually unstable against tidal shearing. Thus the
occurrence of such unstable clumps does not necessarily mean that the disc is
itself a transient phenomenon. The next steps in this investigation are to
explore the effect of the magnetorotational instability on the disc evolution
and to test whether the results presented here persist for longer time-scales
than those considered here.
