Inverse scattering method with variable spectral parameter

In the traditional scheme of the inverse scattering method the spectral parameter of the auxiliary linear problem is usually considered as a constant. The authors propose to consider it as a variable satisfying an over-determined system of differential equations which is determined by the auxiliary linear problem. Nonlinear equations arising in this approach include, as a rule, the explicit dependence on coordinates. Besides the known equations (equation of gravitation, Heisenberg equation in axial geometry etc.) the method makes it possible to construct a number of new integrable equations valuable for applications.