Orbital Stability of Solitary Wave for Eckhaus-Kundu Equation

In this paper, the orbital stability of solitary wave for Eckhaus-Kundu equation is studied. Since the equation we studied is difficult to be expressed as a standard Hamiltonian system, the Grillakis-Shatah-Strauss theory about the orbital stability of soliton solutions for nonlinear Hamiltonian systems cannot be directly applied. By constructing three new conserved quantities and using special techniques and detailed spectral analysis, the above difficulty is overcome, then we obtain the conclusion that the solitary wave of Eckhaus-Kundu equation is orbitally stable.