Photo-erosion refers to the process by which materials, such as soil, rock, or other surfaces, are gradually worn away or eroded due to exposure to light, particularly ultraviolet (UV) radiation from the sun. This phenomenon can occur in various geological and environmental contexts, often influencing the stability and structure of landscapes.

The Cahn–Hilliard equation is a partial differential equation that describes the phase separation and motion of interfaces in a binary mixture or alloy. It is particularly important in materials science, as it models the process by which two phases of a material (such as solid and liquid) separate from each other, leading to the formation of distinct microstructures over time. The equation was introduced by John W. Cahn and John E.

The mild-slope equation is a mathematical representation used in coastal engineering and fluid dynamics to describe the propagation of surface water waves over varying bathymetry (the underwater equivalent of topography). It is especially useful for analyzing wave behavior in coastal areas, where the depth of the water changes gradually.

The Schamel equation is a type of nonlinear partial differential equation that is often used in plasma physics and fluid dynamics to model the evolution of wave phenomena, especially in the context of plasma waves and solitary waves. It is derived from the Korteweg-de Vries (KdV) equation and often appears in studies involving solitons and other wave solutions in dispersive media.

Washburn's equation describes the capillary action of liquids in porous media or thin tubes. It quantifies the rate at which a liquid will diffuse into a porous material due to capillary forces. The equation is often used in the context of materials science, fluid mechanics, and petroleum engineering, among other fields.

Gauss's law is a fundamental principle in electrostatics, part of Maxwell's equations, that relates the electric field generated by a charge distribution to the charge enclosed within a closed surface.