  An analytical solution to the time evolution of decay of one and two
identical noninteracting particles is presented using the formalism of resonant
states. It is shown that the time-dependent wave function and hence the
survival and nonescape probabilities for the initial state of a single particle
and entangled symmetric and antisymmetric initial states of two identical
particles evolve in a distinctive form along the exponential and long-time
nonexponential decaying regimes. In particular, for the last regime, they
exhibit different inverse power of time behaviors.
