Figure 5.

The oscillation period τ is calculated by varying f ₀. Change of τ is much smaller when f ₀ δ ₀ is kept constant as f ₀ δ ₀ = 4 (blue) than when δ ₀ is kept constant as δ ₀ = 2.5 h (red). Other parameters are the same as explained in the caption of Fig. 2. Each point is the average of the data calculated from 10 trajectories, each having 2 × 10³ h length.