CHARACTERISTIC SCALES FOR DOMINATED TIME EVOLUTION

Physical effects associated with the so-called quantum Zeno effect are governed by a time scale associated with first and second moments of the Hamiltonian computed in the initial state of the system. For the s econd moment, this involves matrix elements of the Hamiltonian with re spect to all other states of the system. For metastable states due to confinement by a barrier we find that the characteristic time is appro ximately the geometric mean of the decay time and the traversal (or tu nneling) time. Values taken by these times in some physical systems ar e presented.