TRANSITION FROM QUASI-PERIODICITY TO CHAOS OF A SOLITON OSCILLATOR

We study the properties of the quasiperiodic attractors of the driven and damped sine-Gordon system close to the onset of chaotic dynamics. Our system is a perturbed sine-Gordon equation with ac and dc forcing terms over a finite-size spatial interval. In this system the quasiper iodic trajectories are generated by the incommensurability of the soli ton oscillation and external drive frequencies. For increasing values of the ac drive amplitude the attractors of the system, displayed in a spatially averaged Poincare section, present the characteristic foldi ng and mixing properties of the transition to chaos through quasiperio dicity. In the parameter plane that we scan, the basic features of the transition are not dependent upon the particular ac drive amplitude a nd frequency causing the transition. Analysis of the singularity spect rum f(alpha) of several attractors at the chaotic threshold exhibits g eneral features of the transition.