  The main idea of "Quantum Chaos" studies is that Quantum Mechanics introduces
two energy scales into the study of chaotic systems: One is obviously the mean
level spacing $\Delta\propto\hbar^d$, where $d$ is the dimensionality; The
other is $\Delta_b\propto\hbar$, which is known as the non-universal energy
scale, or as the bandwidth, or as the Thouless energy. Associated with these
two energy scales are two special quantum-mechanical (QM) regimes in the theory
of driven system. These are the QM adiabatic regime, and the QM
non-perturbative regime respectively. Otherwise Fermi golden rule applies, and
linear response theory can be trusted. Demonstrations of this general idea,
that had been published in 1999, have appeared in studies of wavepacket
dynamics, survival probability, dissipation, quantum irreversibility, fidelity
and dephasing.
