RETRACTED: Stability and global Hopf bifurcation in a delayed predator-prey system (Retracted Article)

In this paper, we consider a delayed predator-prey system with same feedback delays of predator and prey species to their growth, respectively. Using the delay as a bifurcation parameter, we investigate the stability of the positive equilibrium and existence of Hopf bifurcation of the model. It is shown that Hopf bifurcations can occur as the delay crosses some critical values. Moreover, the model can exhibit an interesting property, that is, under certain conditions, the positive equilibrium may switch finite times from stability to instability to stability, and becomes unstable eventually. By deriving the equation describing the flow on the center manifold, we can determine the direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions. in addition, special attention is paid to the global continuation of local Hopf bifurcations. Using a global Hopf bifurcation result of Wu [J. Wu, Symmetric functional differential equations and neural networks with memory, Trans. Amer. Math. Soc. 350 (1998) 4799-4838.] for functional differential equations, we may show the global existence of periodic solutions. Computer simulations illustrate the results. (C) 2009 Elsevier Ltd. All rights reserved.