On the zeros of a third degree exponential polynomial with applications to a delayed model for the control of testosterone secretion. (English) Zbl 0982.92008
Summary: We first study the distribution of the zeros of a third degree exponential polynomial. Then we apply the obtained results to a delay model for the control of testosterone secretion. It is shown that under certain assumptions on the coefficients the steady state of the delay model is asymptotically stable for all delay values. Under another set of conditions, there is a critical delay value, the steady state is stable when the delay is less than the critical value and unstable when the delay is greater than the critical value. Thus, oscillations via Hopf bifurcation occur at the steady state when the delay passes through the critical value. Numerical simulations are presented to illustrate the results.
MSC:
92C30 | Physiology (general) |
34K60 | Qualitative investigation and simulation of models involving functional-differential equations |
34K20 | Stability theory of functional-differential equations |
34K25 | Asymptotic theory of functional-differential equations |
92C50 | Medical applications (general) |
93C95 | Application models in control theory |