Stable periodic orbits for delay differential equations with unimodal feedback
Abstract
We consider delay differential equations of the form $ y'(t)=-ay(t)+bf(y(t-1)) $ with positive parameters $a,b$ and a unimodal $f:[0,\infty)\to [0,1]$. It is assumed that the nonlinear $f$ is close to a function $g:[0,\infty)\to [0,1]$ with $g(\xi)=0$ for all $\xi>1$. The fact $g(\xi)=0$ for all $\xi>1$ allows to construct stable periodic orbits for the equation $x'(t)=-cx(t)+dg(x(t-1))$ with some parameters $d>c>0$. Then it is shown that the equation $ y'(t)=-ay(t)+bf(y(t-1)) $ also has a stable periodic orbit provided $a,b,f$ are sufficiently close to $c,d,g$ in a certain sense. The examples include $f(\xi)=\frac{\xi^k}{1+\xi^n}$ for parameters $k>0$ and $n>0$ together with the discontinuous $g(\xi)=\xi^k$ for $\xi\in[0,1)$, and $g(\xi)=0$ for $\xi>1$. The case $k=1$ is the famous Mackey--Glass equation, the case $k>1$ appears in population models with Allee effect, and the case $k\in(0,1)$ arises in some economic growth models. The obtained stable periodic orbits may have complicated structures.
- Publication:
-
arXiv e-prints
- Pub Date:
- July 2024
- DOI:
- 10.48550/arXiv.2407.18016
- arXiv:
- arXiv:2407.18016
- Bibcode:
- 2024arXiv240718016B
- Keywords:
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- Mathematics - Dynamical Systems;
- 34K30;
- 34K39;
- 65G30