Orbital stability of solitary waves of moderate amplitude in shallow water

Agraïments: This work was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) and the WWTF project MA09-003 "The flowbeneath a surface water wave" of the Vienna Science and Technology Fund. The authors gratefully acknowledge helpful suggestions by Prof. Gasull. We study the orbital stability of solitary traveling wave solutions of an equation for surface water waves of moderate amplitude in the shallow water regime. Our approach is based on a method proposed by Grillakis, Shatah and Strauss in 1987 [1], and relies on a reformulation of the evolution equation in Hamiltonian form. We deduce stability of solitary waves by proving the convexity of a scalar function, which is based on two nonlinear functionals that are preserved under the flow.