biophysics bäcklundtransformations chaoticbehaviorinsystems coherence(optics) congresses differential differentialequations dynamics evolutionequations geometry instantons integralequations integratedoptics inversescatteringtransform latticetheory mathematics nonlinear nonlinearoptics nonlineartheories nonlinearwaves numericalsolutions partial quantumfieldtheory scattering(mathematics) signalprocessing solidstatephysics theoryof wave-motion