  Numerical simulations of the scattering of a linear plane wave incoming onto
a nonlinear medium (sine-Gordon) reveals that: i) nonlinearity allows energy
transmission in the forbidden band, ii) this nonlinear transmission occurs
beyond an energy threshold of the incoming wave, iii) the process begins (at
the threshold) with large amplitude breathers, and then energy is generically
transmitted both by kink-antikink pairs and breathers.
