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Positive periodic solution for a two-species ratio-dependent predator-prey system with time delay and impulse. (English) Zbl 1111.34051
The paper deals with a predator-prey model with delay and impulses of the form \align \dot{x}(t)&=x(t)\left(b_1(t)-a_1(t)x(t)-{{c(t)y(t)}\over{m_1(t)y(t)+x(t)}}\right),\\ \dot{y}(t)&=y(t)\left(-b_2(t)+{{a_2(t)x(t-\tau)}\over{m_2(t)y(t-\tau)+x(t-\tau)}}\right), \quad\text{for }t\ne t_k,\endalign \align x(t^+_k)-x(t^-_k)& =c_kx(t_k), \qquad y(t^+_k)-y(t^-_k)= d_ky(t_k), \quad (x(0+), y(0+))=(x_0,y_0),\\ (x(t), y(t))&=(\varphi_1(t), \varphi_2(t)),\text{ for }-\tau\leq t\leq 0.\endalign The authors apply the continuation fixed-point theorem of coincindence degree theory to provide sufficient conditions for the existence of a periodic solution of the problem.

##### MSC:
 34K13 Periodic solutions of functional differential equations 34K45 Functional-differential equations with impulses 34K60 Qualitative investigation and simulation of models 92D25 Population dynamics (general)
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##### References:
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