Fig. 10

Continuation of the leading characteristic root and Hopf detection with delay. (a) Real part of the dominant eigenvalue \(\Re (\lambda )\) versus delay \(\tau\) showing a smooth crossing of the imaginary axis at the critical value \(\tau _c \approx 37.65\), marking the onset of a Hopf bifurcation. (b) Repeated computation confirming identical Hopf crossing behaviour. For \(\tau <\tau _c\) the system is stable; for \(\tau>\tau _c\), sustained oscillations emerge.