Normal diffusion has mean-squared displacement ⟨x²⟩ ~ t (Brownian motion). In disordered media, particles get trapped at random sites and exhibit subdiffusion: ⟨x²⟩ ~ t^α with 0 < α < 1. This continuous-time random walk (CTRW) with power-law waiting times τ^(−1−α) captures anomalous transport in crowded cells, amorphous semiconductors, and porous rocks.
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