Arbitrarily large numbers of kink internal modes in inhomogeneous   sine-Gordon equations
  We prove the existence of an infinite number of internal (shape) modes of sine-Gordon solitons in the presence of some inhomogeneous long-range forces, provided some conditions are satisfied. 
J. A. Gonz\'alez, A. Bellor\'in, M. A. Garc\'ia-\~Nustes, L. E.   Guerrero, S. Jim\'enez and L. V\'azquez
nlin.PS