I want to prove the existence of a periodic solution for this differential

$$ \frac{dN}{dt}=(1+cos(\alpha t))r(c-N)-\mu N. $$

Plotting the solution of this equation in Matlab produces the graph below enter image description here

I was thinking of using a Poincare return map to prove the existence? and then using Floquet Theory for the stability? Would this work?

Any help would be much appreciated.


  • 1
    $\begingroup$ Yes, it can be done in a fairly elementary way. The Poincare map takes $[-1,\frac{4rc}{2r+\mu}]$ into its interior, and the existence of its fixed point is a consequence of the Intermediate Value Property. The resulting periodic solution is globally asymptotically stable, because the difference of any two solutions satisfies a linear homogeneous ODE which can be solved in a closed form. $\endgroup$
    – user539887
    May 3 '19 at 10:55

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