Nearly Integrable Infinite-Dimensional Hamiltonian Systems

The book is devoted to partial differential equations ofHamiltonian form, close to integrable equations. For suchequations a KAM-like theorem is proved, stating thatsolutions of the unperturbed equation that are quasiperiodicin time mostly persist in the perturbed one. The theorem isapplied to classical nonlinear PDE's with one-dimensionalspace variable such as the nonlinear string and nonlinearSchr|dinger equation andshow that the equations have"regular" (=time-quasiperiodic and time-periodic)