Generation of high-energy localized vibrational modes in nonlinear Klein-Gordon lattices

We study numerically the exchange of energy and momentum between colliding breathers in nonlinear Klein-Gordon lattices as a means of obtaining localization of energy. Statistical calculations show a clear preference of the larger breather to take energy from the smaller one in the whole energy range of interest. Thus it represents an effective mechanism for energy localization in nonlinear Klein-Gordon lattices, originating from the discreteness and nonintegrability of the system. To get initial conditions for our simulations we numerically calculate exact single-frequency static breather solutions using a technique recently discovered by Flach [Phys. Rev. E 51, 3579 (1995)].