Interactions of breathers and solitons in the extended Korteweg-de Vries equation

The extended Korteweg-de Vries model governs the evolution of weakly dispersive waves under the combined influence of quadratic and cubic nonlinearities, and is relevant to finite-amplitude wave motions in the atmosphere and the ocean. Analytic expressions for a multi-soliton are obtained by the Hirota bilinear method, and are shown to agree with those for isolated solitary waves or breathers obtained earlier in the literature. In particular, the interaction of a breather and a soliton can now be studied. Both the soliton and the breather retain their identities after interaction except for some phase shifts. Detailed examination of the interaction process shows that the profile of the breather will depend critically on the polarity of the colliding soliton.