Multisoliton collisions in nearly integrable systems

We describe basic features of multisoliton collisions in nearly integrable systems taking a perturbed nonlinear Schr\"odinger equation as an example. Collision of two solitons is shown to become inelastic only due to radiation losses, so that the change of the soliton parameters is small (~ε², where ε is the perturbation amplitude). For three-soliton collisions we demonstrate, by using a simplectic numerical integration, the existence of a nontrivial nonradiative energy exchange between the colliding solitons already in the first order in ε.