Regimes in the theory of wavepacket dynamics (2000)

In 1999-2000 I have proposed a generalized identification of the Fermi-golden-rule (FGR) regime also called Wigner or Kubo regime. The standard FGR condition states that the induced decay time (${t_0=\hbar/\Gamma}$) should be larger than the classical correlation time [equivalent phrasing: $\Gamma$ should be smaller than the bandwidth of the perturbation matrix]. The generalized condition involves a generalized FGR-Wigner time. For example for DC driving of a quantized chaotic system ${t_0=(\hbar^2/D_E)^{1/3}}$, where $D_E$ is the diffusion in energy space as determined by the Kubo formula.
 
The idea of regimes (FGR vs non-FGR) in the context of LDOS / wavepacket dynamics / theory of response studies has been later adopted (in 2001) by other groups in the context of quantum irreversibilty and fidelity studies, and has proved to be a useful concept.