On the stability of periodic orbits in delay equations with large delay
  We prove a necessary and sufficient criterion for the exponential stability of periodic solutions of delay differential equations with large delay. We show that for sufficiently large delay the Floquet spectrum near criticality is characterized by a set of curves, which we call asymptotic continuous spectrum, that is independent on the delay. 
Jan Sieber, Matthias Wolfrum, Mark Lichtner, Serhiy Yanchuk
math.DS