Dynamics of an oscillator with delay parametric excitation

This paper involves the dynamics of a delay limit cycle oscillator being driven by a time-varying perturbation in the delay:ẋ=−x(t−T(t))−ϵx3with delay T(t)=π2+ϵk+ϵcosωt. This delay is chosen to periodically cross the stability boundary for the x=0 equilibrium in the constant-delay system.