Boundary of two frequency behaviour in a system of three weakly coupled electronic oscillators

We review and report observations of complex dynamics associated with loss of stability of two frequency quasiperiodicity at a saddle-node bifurcation of invariant two-tori. In particular, for a system of three weakly coupled electronic oscillators we find 'bubbles' in parameter space interrupting a curve on which there is a saddle-node bifurcation of two-tori. These are comparable to Chenciner's bubbles found near a codimension two bifurcation of a planar map. (C) 1998 Elsevier Science Ltd. All rights reserved.