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Periodic solutions of delayed periodic Nicholson’s blowflies models. (English) Zbl 1093.34554
The author considers the modified Nicholson blowflies model \[ \frac{dN}{dt} (t) =-\delta (t)N(t)+P(t)N(t-\sigma (t)) \exp (-a (t)N(t-\tau (t))), \tag \(*\) \] where \(\delta \in C(\mathbb R,\mathbb R), \;P, \sigma ,\tau \in C(\mathbb R, [0,\infty))\), and \(a \in C(\mathbb R , (0,\infty))\) are \(\omega\)-periodic functions with \(\int^\omega_0 \delta (t) \,dt >0.\) He derives some easily verifiable sufficient conditions for the existence of a periodic solution to \((*)\). The proof is based on the coincidence degree.

MSC:
34K13 Periodic solutions to functional-differential equations
92D25 Population dynamics (general)
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