Anomalous diffusion through coupling to a fractal environment: Microscopic derivation of the "whip-back"effect

Two models for quantum Brownian motion -the Oscillator Bath (OB) model and the Random Band-Matrix (RBM) model-are compared and a relation between the spectral density function I (ω) and the variance bar V ab 2 is established. The extension to a fractal environment is then considered and the microscopic origin of anomalous diffusion is discussed. In particular, it is shown that the asymptotic behavior of the normalized velocity auto-correlation function (VACF) is entirely determined by the band form factor. This allows for a microscopic derivation of the "whip-back"effect.