Anomalous Diffusion — CTRW & Montroll-Weiss Theory

Continuous Time Random Walk with power-law waiting times · ⟨x²⟩ ~ t^α

Parameters

α<1 sub-diffusion
α=1 normal
α>1 super-diffusion
Montroll-Weiss theory: CTRW with waiting time PDF ψ(t) ~ t^{-1-α} gives MSD ⟨x²(t)⟩ ~ t^α.

α < 1: sub-diffusion (trapping, glassy systems)
α = 1: normal Brownian motion
α > 1: super-diffusion (Lévy flights)

Mittag-Leffler function E_α(-λt^α) governs relaxation instead of simple exponential.