Interaction of a kink soliton with a breather in a Fermi-Pasta-Ulam chain.

The collision process between a breather and moving kink soliton is investigated both analytically and numerically in Fermi-Pasta-Ulam (FPU) chains. As it is shown by both analytical and numerical consideration low amplitude breathers and soft kinks retain their shapes after interaction. Low amplitude breather only changes the location after collision and remains static. As the numerical simulations show, the shift of its position is proportional to the stiffness of the kink soliton, what is in accordance with the analytical predictions made in this paper. The numerical experiments are also carried out for large amplitude breathers and some interesting effects are observed: The odd parity large amplitude breather does not change position when colliding with a widely separated soft kink-antikink pair, while in the case of a closely placed kink-antikink pair the breather transforms into the moving one. Therefore it is suggested that the "harmless" objects similar to the kink solitons in FPU chains could be used in order to displace or move the strongly localized structures in realistic physical systems. In particular, the analogies with quasi-one-dimensional easy-plane-type spin structures are discussed.