This paper is concerned with the orbital stability/instability of solitary waves for coupled BBM equations which have Hamiltonian form. The explicit solitary wave solutions will be worked out first. Then by detailed spectral analysis and decaying estimates of solutions for the initial value problem, we obtain the orbital stability/instability of solitary waves.
In this paper, we investigate a class of Hamiltonian systems arising in nonlinear composite media. By detailed analysis and computation we obtain a decaying estimates on the semigroup and prove the orbital instability of two families of explicit solitary wave solutions （slow family in anisotropic case and solitary waves in isotropic case）, which theoretically verify the related guess and numerical results.
