Figure 9. Phase portrait of birhythmicity for Model 3.

Simulation of the two oscillatory regimes in the phase space for Model 3. The dashed lines represent the thresholds K_Mc, K_Mn and K for P, K_P for Mn. The parameter values are the same as for Figure 6 (K_Mn = 0.1 nM) except K_Mc = 0.4 nM, K = 0.05 nM, K_P = 2 nM, d_P = 3 h⁻¹, Mc¹¹ = Mc²¹ = Mc¹² = 0, Mc²² = 5 nM, Mc¹³ = 9 nM, Mc²³ = 11.3 nM, Mc¹⁴ =  Mc²⁴ = 25 nM. Note that, since the degradation constants d_Mn and d_P have the same values, the trajectories in each domain are straight lines.