  Consider N particles moving independently, each one according to a
subcritical continuous-time Galton-Watson process unless it hits 0, at which
time it jumps instantaneously to the position of one of the other particles
chosen uniformly at random. The resulting dynamics is called Fleming-Viot
process. We show that for each N there exists a unique invariant measure for
the Fleming-Viot process, and that its stationary empirical distribution
converges, as N goes to infinity, to the minimal quasi-stationary distribution
of the Galton-Watson process conditioned on non-extinction.
