"Short Time Quantum Revivals in Chaotic Quantum Systems."
Classical dynamical systems are subject to the famous Poincare recurrence theorem: if the phase space available to the system is finite, the system will eventually return arbitrarily close to its initial state. In quantum systems having classical analogues, the initially localized wave packets will spread and disperse as they propagate, but will reconstruct after a relatively short time. The perfect and fractional revivals in such systems are considered a consequence of a special (e.g. quadratic) distribution of energy levels. In quantum systems with chaotic classical dynamics this reason for early revivals is no longer valid. For extended wave packets, however, there is an interplay of several other factors, such as selection of the energy levels, high dimensionality, and spatial overlap of the initial and final states, that allow early revivals to occur. Since Poincare recurrences are quite common for a variety of dynamical systems, both classical and quantum, I am going to discuss these factors in the context of a classical and a quantum systems.