Aa. Zabolotskii, DEFORMED WHITHAM EQUATIONS FOR SOME NEAR-INTEGRABLE SYSTEMS, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 56(4), 1997, pp. 4813-4821
A perturbation approach for some near-integrable systems with periodic
boundary conditions is developed. Deformed Whitham equations includin
g perturbaton terms of a special type are derived in a common form for
Ablowitz-Kaup-Newell-Segur models, This approach is used for analysis
of the generation of a dense packet of solitons in a model of a two-l
evel laser with pumping of the upper level and relaxation.