Lax pair

A Lax pair is a mathematical construct used primarily in the study of integrable systems, particularly in the framework of soliton theory and the theory of nonlinear partial differential equations. It provides a way to understand the integrability of a system and is particularly useful for finding solutions to nonlinear equation systems. A Lax pair consists of two matrices, \( L \) and \( M \), which depend on a parameter \( \lambda \) (often interpreted as a spectral parameter).