Asymptotic two-soliton solutions in the Fermi-Pasta-Ulam model
  We prove the existence of asymptotic two-soliton states in the Fermi-Pasta-Ulam model with general interaction potential. That is, we exhibit solutions whose difference in $\ell^2$ from the linear superposition of two solitary waves goes to zero as time goes to infinity. 
A. Hoffman and C.E. Wayne