This section is about frequency dispersion for waves on a fluid layer forced by gravity, and according to linear theory.

According to linear theory for waves forced by gravity, the phase speed depends on the wavelength and the water depth.

As the primary modes grow and distort the mean flow, they begin to exhibit nonlinearities and linear theory no longer applies.

On large scales, gravity competes with cosmic expansion, and structures grow according to linear theory.

The scalar field, is a function of a set of spatial variables, , and a time variable, t. We first consider the linear theory.

This linear theory is often used to get a quick and rough estimate of wave characteristics and their effects.

Airy wave theory is a linear theory for the propagation of waves on the surface of a potential flow and above a horizontal bottom.

Everything discussed here is based on the linear theory of an ideal fluid.

The most basic scalar field theory is the linear theory.

Airy wave theory is the linear theory for the propagation of gravity waves on the surface of a fluid.