Figure 4
Schematic change of the real parts of the two eigenvalues of an originally stable fixed point 
. (a) 
has two negative real eigenvalues (compare also Figure 2). At 
, they coalesce to a pair of complex conjugate eigenvalues whose real part increases with Ï„. The system undergoes a Hopf bifurcation and the fixed point 
becomes unstable when this real part crosses the 
-axis at 
. For large time delays, the two eigenvalues are real from 
and approach the values 0 and 
. (b) Similar course, 
, has a pair of complex conjugate eigenvalues.