Abstract
In this paper we study and investigate the Lag synchronization (LS) of hyperchaotic complex nonlinear systems by using passive control theory. LS of these hyperchaotic complex systems via passive control has not received enough attentions, as far as we know, in the literature. Based on the property of the passive system the passive controller is stated to achieve LS of two identical hyperchaotic complex Lorenz systems. These complex systems appear in many important fields of physics and engineering. The analytical results of the controllers, which have been calculated by using our scheme, are tested numerically and good agreement is obtained.