Characteristic algebras of the discrete equations
It is well known that the characteristic Lie algebras, introduced by A.B. Shabat in 1980, play the crucial role in studying the hyperbolic type partial differential equations. For example, if the haracteristic algebra of the equation is of finite dimension, then the equation is solved in quadratures, if the algebra is of finite growth then the equation is integrated by the inverse scattering method. Recently it has been observed by A.V. Zhiber that the characteristic algebra provides an effective tool to classify the nonlinear hyperbolic equations. However, the characteristic algebras has not yet been used to study the discrete equations.
The notion of the characteristic Lie algebra of the discrete hyperbolic type equation is introduced. An effective algorithm to compute the algebra for the equation given is suggested. Examples and further applications are discussed.