A spectral view of wave propagation


  • L. B. Felsen


Wave propagation in environments characterized by weakly nonseparable conditions can be described by adiabatic modification of spectra pertaining to the unperturbed separable case. Recent developments are reviewed here, with emphasis on approximate adiabatic transform relations and adiabatic invariants, which permit reduction of the direct weakly nonseparable wave problem to spectral form and, conversely, reconstruction of wave spectra from measured data.