RIEMANN-HILBERT PROBLEM, INTEGRABILITY AND REDUCTIONS

The present paper is dedicated to integrable models with Mikhailov reduction groups G(R) similar or equal to D-h. Their Lax representation allows us to prove, that their solution is equivalent to solving Riemann-Hilbert problems, whose contours depend on the realization of the G(R)-action on the spectral parameter. Two new examples of Nonlinear Evolution Equations (NLEE) with D-h symmetries are presented.