Modulating coherence resonance in non-excitable systems by time-delayed   feedback
  We propose a paradigmatic model system, a subcritical Hopf normal form subjected to noise and time-delayed feedback, to investigate the impact of time delay on coherence resonance in non-excitable systems. We develop analytical tools to estimate the stationary distribution and the time correlations in nonlinear stochastic delay differential equations. These tools are applied to our model to propose a novel quantity to measure coherence resonance induced by a saddle-node bifurcation of periodic orbits. 
Paul M. Geffert, Anna Zakharova, Andrea V\"ullings, Wolfram Just,   Eckehard Sch\"oll
nlin.AO