“…Via the Smale-Birkhoff homoclinic theorem (Guckenheimer and Holmes [1983]), this situation leads to chaotic dynamics of phase points in the vicinity Orbits homoclinic to resonance bands arise in many physical models, particularly those models that are obtained by transforming coordinates into a rotating reference frame and averaging over a fast phase. Examples of such models are Bishop, Flesch, Forest, McLaughlin, and Overman [1990] in the theory of Josephson's junctions; David, Holm, and Tratnik [1990] in nonlinear fiber optics; Holm and Kovačič [1992] in laser-matter interaction; Holmes [1986], Gu and Sethna [1987], and Feng and Sethna [1989], [1990] in the theory of water waves; and Yang and Sethna [1991] in the theory of vibrating plates. All the resonant periodic motions of such physical models, that is, periodic motions whose frequencies coincide with the frequency of the rotating frame, become circles of equilibria.…”