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Existence of positive periodic solutions for a periodic logistic equation. (English) Zbl 1031.45005
The paper deals with existence of $$\omega$$-periodic solutions for the following generalized logistic equations: $x'(t)=\pm x(t)\left[f\left(t, \int_{-r(t)}^{-\sigma(t)}x(t+s) d\mu(t,s)\right)-g(t, x(t-\tau(t, x(t))))\right],$ where $$\sigma,r\in C(\mathbb{R},(0,\infty))$$ are $$\omega$$-periodic functions with $$\sigma(t)<r(t)$$, $$f$$, $$g$$, $$\tau$$, $$\mu$$ $$\in C(\mathbb{R}\times\mathbb{R},\mathbb{R})$$ are $$\omega$$-periodic functions with respect to their first variable and nondecreasing with respect to their second variable. Using the well known Mawhin’s coincidence degree theorem [R. E. Gaines and J. L. Mawhin, Coincidence degree and nonlinear differential equations, Springer, Berlin (1977; Zbl 0339.47031), p. 40], the authors prove the existence of at least one positive $$\omega$$-periodic solution for each of the above equations.

##### MSC:
 45J05 Integro-ordinary differential equations 45G10 Other nonlinear integral equations 45M15 Periodic solutions of integral equations
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##### References:
 [1] Kuang, Y., Delay differential equations with applications in population dynamics, (1993), Academic Press New York · Zbl 0777.34002 [2] Gaines, R.E.; Mawhin, J.L., Coincidence degree and nonlinear differential equations, (1977), Springer Berlin · Zbl 0326.34021
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