Driven response of time delay coupled limit cycle oscillators
  We study the periodic forced response of a system of two limit cycle oscillators that interact with each other via a time delayed coupling. Detailed bifurcation diagrams in the parameter space of the forcing amplitude and forcing frequency are obtained for various interesting limits using numerical and analytical means. In particular, the effects of the coupling strength, the natural frequency spread of the two oscillators and the time delay parameter on the size and nature of the entrainment domain are delineated. The system is found to display a nonlinear response on certain critical contours in the space of the coupling strength and time delay. Time delay offers a novel tuning knob for controlling the system response over a wide range of frequencies and this may have important practical applications. 
D. V. Ramana Reddy, A. Sen and G. L. Johnston