Noise-induced dynamic symmetry breaking and stochastic transitions in ABA molecules: II. Symmetric-antisymmetric normal mode switching

A typical trajectory in action-angle variables that shows antisymmetric-to-symmetric normal mode transitions in ABA molecules as a function of dimensionless time. The plot (a) represents the time-dependence of AB and BA bond phase difference: the stable oscillations around π/2 and 3π/2 indicate antisymmetric normal mode behavior, while the stable oscillations around π correspond to symmetric normal-mode behavior. Plot (b) shows the corresponding time-dependence of the local action variables J1 and J2: the complete energy exchange between J1 and J2 indicates the normal-mode behavior.