Multiple positive periodic solutions of nonlinear functional differential system with feedback control

AbstractIn this paper, we employ Avery–Henderson fixed point theorem to study the existence of positive periodic solutions to the following nonlinear nonautonomous functional differential system with feedback control: dxdt=−r(t)x(t)+F(t,xt,u(t−δ(t))),dudt=−h(t)u(t)+g(t)x(t−σ(t)). We show that the system above has at least two positive periodic solutions under certain growth condition imposed on F