Nearly Integrable Infinite-Dimensional Hamiltonian Systems

The book is devoted to partial differential equations of Hamiltonian form, close to integrable equations. For such equations a KAM—like theorem is proved, stating that solutions of the unperturbed equation that are quasiperiodic in time mostly persist in the perturbed one. The theorem is applied to classical nonlinear PDE's with one—dimensional space variable such as the nonlinear string and nonlinear Schr|dinger equation andshow that the equations have "regular" (=time—quasiperiodic and ti...