Fig. 2

Bifurcation curves in the $(k_1,k_2)$-plane. ${\tau }_1=11.6$ and ${\tau }_2=20.3$. The right plot shows a detail of the first quadrant only. Blue shows the conditions for fold or transcritical bifurcations (Equations 14a and 14b) and red and magenta depict Hopf bifurcations; equations ${\mathbf{h}}_{+}$ and ${\mathbf{h}}_{-}$, respectively. The gray area represents the stability region as in Corollary 4. The full stability region is hatched in the right diagram.