Figure 3
From: Data-driven modeling of subharmonic forced response due to nonlinear resonance
The phase space of a nondegenerate integrable \(n\)-degree of freedom system is mostly foliated by invariant \(n\)-tori containing quasiperiodic orbits. Tori with resonant frequencies are instead filled by infinitely many periodic orbits, such as the three-periodic orbit illustrated on the middle torus. Upon every third revolution about the vertical axis, this orbit closes up with itself.
