Figure 4.

Three-frequency devil's staircase. Contrary to the case of periodically driven systems, where plateaux represent periodic solutions, plateaux here represent quasiperiodic solutions (only the third frequency is represented in the ordinate). We have investigated these properties in three different systems: the quasiperiodic circle map, a system of coupled electronic oscillators, and a set of ordinary nonlinear differential equations, with the same qualitative results (23) that confirm the theoretical predictions (11).