Important parameters for linearity are integral nonlinearity and differential nonlinearity. As a result of the interplay of nonlinearity and dispersion, solitons can form. The model does not account for fading, frequency selectivity, interference, nonlinearity or dispersion. Kerr nonlinearity underlies a wide variety of optical phenomena. Silicon has a focusing Kerr nonlinearity, in that the refractive index increases with optical intensity. All convolution layers use Leaky ReLU nonlinearity activation function. It can take place only in media with anisotropy of third order nonlinearity. Differential gain is a special case of gain nonlinearity. For larger amplitudes, the nonlinearity is pronounced. Specific loudness is a compressive nonlinearity and varies at certain levels and at certain frequencies. More specifically, the probabilistic interpretation considers the activation nonlinearity as a cumulative distribution function. The nonlinearity of the EFE distinguishes general relativity from many other fundamental physical theories. For example, the method can fail if the system emphasizes higher harmonics of the nonlinearity. This nonlinearity presents the most severe problem for optical communication applications. This is due to the nonlinearity of the generation process, phase matching and ionization.