The scope of this book is to present in a systematic and unified manner the ray method (in its various forms) for studying nonlinear wave propagation in situations of physical interest (essentially fluid dynamics and plasma physics). The book could be used for an advanced graduate course on nonlinear waves. It should also be of interest to applied mathematicians, physicists and engineers, working in areas related to nonlinear waves.

Presents in a systematic and unified manner the ray method, in its various forms, for studying nonlinear wave propagation in situations of physical interest, essentially fluid dynamics and plasma physics.