  We study the dynamics of a simple model for quantum decay, where a single
state is coupled to a set of discrete states, the pseudo continuum, each
coupled to a real continuum of states. We find that for constant matrix
elements between the single state and the pseudo continuum the decay occurs via
one state in a certain region of the parameters, involving the Dicke and
quantum Zeno effects. When the matrix elements are random several cases are
identified. For a pseudo continuum with small bandwidth there are weakly damped
oscillations in the probability to be in the initial single state. For
intermediate bandwidth one finds mesoscopic fluctuations in the probability
with amplitude inversely proportional to the square root of the volume of the
pseudo continuum space. They last for a long time compared to the non-random
case.
