Abstract:
We study the effect of the resonant phase locking in the problem of
the sine-Gordon equation breather under the action of a small oscillating
external force with slowly varying frequency. We obtain equations determining
the time evolution of the parameters of the perturbed breather. We describe
the regular asymptotic procedure of averaging such equations and show that
the averaged equations in the leading order already well describe
the phenomenon of resonant phase locking in which the breather oscillations are
strongly excited. We obtain necessary and sufficient conditions for the phase
locking relating the rate of the perturbation frequency variation and its
amplitude to the initial data of the breather.