Overdiffussie

Overdiffussie is a term used in some Dutch-language scientific writings to describe a diffusion process in which the spread of a quantity—such as particles, heat, or information—proceeds more rapidly or extensively than predicted by classical Fickian diffusion. The term emphasizes excessive or anomalous spreading and is not a universally standardized category in diffusion theory.

In practice, overdiffussie can arise in systems with heterogeneous or active media, where diffusivity depends on position or time, or where transport is aided by external fields, advection, or active motion. It is often discussed alongside concepts such as superdiffusion and anomalous diffusion, including Lévy-type transport, though overdiffussie is not typically treated as a distinct formal model. Descriptions of overdiffussie may involve time-dependent or nonlinear diffusion equations, nonlocal transport, or other frameworks that yield faster-than-Fickian spreading.

Mathematically, the notion is used to characterize regimes in which the mean squared displacement grows more quickly than linearly with time, or where the effective diffusivity increases with scale or duration. Researchers may apply time- or space-dependent diffusivity, fractional diffusion equations, or hybrid models to capture the observed dynamics. Applications span physical contexts like porous media and plasmas, biological systems with active transport, and social or ecological networks where information or individuals disperse rapidly.

Etymology reflects its Dutch roots: over- meaning excessive and diffusie meaning diffusion. The term is informal and not universally standardized, and its precise meaning can vary by discipline and author. See also diffusion, anomalous diffusion, superdiffusion, Lévy flights, and fractional diffusion.